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BROACHES AND BROACHING
McGraw.J///}ook Góże f
P U B L | S H E R S O F B O O K S R O R_,
Coal Age & Electric Railway Journal
Electrical World v Engineering News-Record
American Machinist v The Contractor
Engineering & Mining Journal & Power
Metallurgical & Chemical Engineering
Electrical Merchandising

|B R () A (; H E S
AND
|B R () A (; H | N (;
BY
ETHAN VIALL
MANAGING EDITOR AMERICAN MACHINIST
Al EMBER AMERICAN SOCIETY OF MECHANICAL ENGINEERS
MEMBER FRANKLIN INSTITUTE, AUTHOR OF UNITED
STATES ARTILLERY AMMUNITION, UNITED
STATES RIFLES AND MACHINE GU NS.
FIRST EDITION
McGRAW-HILL BOOK COMPANY, INC.
239 WEST 39TH STREET, NEW YORK
LONDON: HILL PUBLISHING CO., LTD.
6 & 8 BOUVERIE ST., E. C.
1918
CoPYRIGHT, 1918, BY THE
McGRAw-HILL BOOK COMPANY, INC.
“T H E NAA F L E P R E S S Y O R K PA
PREFACE
Just how far back the knowledge of broaching dates is not known, though
the great Leonardo Da Vinci, who was born in 1452 and died in 1519, made
numerous sketches in his note books, depicting the broach in practically
the forms used today, but it is extremely doubtful if he or his immediate
successors made use of them; it shows, nevertheless, how far ahead the
gigantic genius of the Florentine saw, to outline tools and machines that are
just being appreciated.
However early the broach may have been invented, it is only in recent
years that it has shown signs of taking the place its merits deserve. As one
of the numerous branches of mechanics which owes its principal develop-
ment to the evolution of the automobile, broaching has grown enormously in
application, and is used today to a considerable extent in almost every branch
of mechanical industry, and so quietly has it spread that few realize its great
importance.
It is to bring to the attention of those who would know more of broaching
work and machinery as it exists at present that this book has been compiled,
thereby placing in their hands data that will enable them to judge whether
it is applicable to their particular class of work or not, and if it is, to give
them whatever working directions and advice I have been able to gather.
ETHAN VIALL.
NEw York,
January, 1918.
CONTENTS
PREFACE .
CHAPTER I
BROACHING AND BROACHING TOOLS. . e e º e s e g º º e º e º e s 4 & 8
A Definition of Broaching—The Uses of Broaching Tools—Types of Broaches.
CHAPTER II
STANDARD TYPES OF BROACHING MACHINEs. e s e s = e s e e e s & is
The Pull Type of Machine–Machines of the Rack-and-Pinion Class—Machines
for Push Broaching—A Screw-operated Vertical Press—A Hand-operated Press.
CHAPTER III
ExAMPLES OF PULL BROACHING Work AND PRACTICE. . tº tº e º 'º & E - º
Cutting Keyways—Broaching Machine Made from a Lathe-A Burton Keyway
Machine–Cutting a Keyway in a Taper Hole–Broaching Spiral Keyways—
Broaching Round Holes—Broaching and Burnishing Bearings—Another Bearing
Broach—Broaching Square Holes—Broaching Tapered Square Holes—Broaching
Square Holes in a Jig–Broaching Rectangular Holes—Another Vise Job—Finish-
ing Ends of Expanding Rings—Broaching Four-spline Holes—A Double-end
Broaching Machine–Broaching an Internal Cam-Broaching a 22-in. Internal
Gear—Broaching Several Pieces at Once—Largest Broaching Machine ever Built
—A Very Unusual Job—External Broaching—Broaching Flats on Bearings—
Broaching the Outside of a Core for an Automobile Wheel—Two Vertical Pull
Broaching Machines—Lubricant Used for Steel Work—Time Required to Broach
Various Kinds of Work. *
CHAPTER IV
EXAMPLES OF PUSH BROACHING WoRK AND PRACTICE . . 8 * * * * * * *
Broaching Universal Joints—Broaching Connecting Rod Ends—Broaching Parts
of Lifting Jacks—Broaching Revolver Frames—Wrench Work—A Sub-press for
Motor Cams—Using Single Tooth Broaches—External Broaching Work—The
Mandrel Press as a Broaching Machine—Making Use of a Sub-press—A Hand
Broaching Press—Turret Broach for a Mandrel Press—Broaching Keyways to a
Shoulder—Cutting Oil Grooves in Eight Holes at Once–Horizontal Hand
Broaching Machine–Broaching on a Shaper—A Surfacing Operation—A Shaper
Turret—Broaching on a Planer—Broaching Spiral Slots in a Lathe-A Turret
Broaching Machine for Gun Recoil Valves—Turret Machine for Small Square
Holes.
PAGE
66
vii
viii CONTENTS
CHAPTER V
THE DESIGN OF PULL BROACHES . . . . . . . . . . . . . . . . . . . . . . Ioé
per Tooth—Differential Pitch—Design of Keyway Broaches—Design of Round
Broaches—Design of Square Broaches—Brown & Sharpe Broaching Practice—
To Save Time in Broaching Out Square Holes—Dimensions for Hexagon, Six-
spline and Button Broaches—Securing Clearance in Sliding Gear Splines—Design
of Spline Broaches—Repair and Upkeep of Spline Broaches—Broaches for Motor-
cycle Gears—Design of Diagonal Tooth Broaches—A Key-slot Broach—Inserted
Tooth Broaches—An Adjustable Broach—Broach Holders or Couplings–An
Eccentric Lock—Work Bushings and Work Holding Fixtures—Gear Holding and
Marking Fixtures—A Motor Cam Fixture.
CHAPTER VI
THE DESIGN OF PUSH BROACHES. . . . . . . . . . . . . . . . . . . . . . . I 57
Formulas and Data Available for Push Broaches—Tables of Push Broach Dimen-
sions—Squaring Holes in Universal Joints—Sizes for Babbitted Bearings—
Broaches for Bronze or Babbitt—Push Broaches for a Variety of Work—A
Built-up Internal Broach—Expanding Hollow Cylinders—A Pair of Peculiar
Broaches—A Diamond Tooth Broach—Power Required to Broach Steel.
CHAPTER VII
MAKING BROACHES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
Pull Broach Work—Turning Long, Slender Broaches—Planing Broach Blanks—
Milling the Teeth—Milling the Slot in the Shank—Angular Taper Broach Milling
—Making Push Broaches for Steel Work—Hardening Broaches—Grinding
Broaches—Testing Depth of Cut Per Tooth.
APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
BROACHES AND BROACHING
CHAPTER I
BROACHING AND BROACHING TOOLS
Just what machine work may be classed as broaching and what may not,
is, like So many other mechanical questions, not so easy to answer as it looks.
It is common shop practice to class many shop jobs worked out with a
single-point tool as broaching, whether the work is done on a shaper, punch
press, keyseater, mandrel press or some other machine or device. However,
no one ventures to call the work of a slotter broaching.
What then are the boundaries within which work may properly be classed
as broached work? Everyone admits without argument, that holes finished
to certain sizes or shapes by the use of tools having a number of teeth of
increasing size is broaching, no matter whether the tools are pushed or pulled
through. -
Again, it is evident that a hole finished to size at one pass, by means of a
single-point tool forced through by any means whatever, whether by the
ram of a shaper, a punch press, a mandrel press or a hammer, is not broaching.
It is either punching or drifting. Neither can the working out of a hole or
recess, in a number of cuts, by means of a single-point tool held in a shaper,
punch press or other machine, be called broaching. It is slotting.
A case that is not so clear, perhaps, is the work of a keyseater using a
multiple-tooth cutter. Where the keyseat is finished at one pass with a tool
having a number of teeth of increasing size, it is broaching. If it requires
Several passes to finish the keyseat with this kind of tool, it is still broaching,
as the successive cuts simply take the place of the passage of Several broaches
of increasing size. However, if the tool has a number of teeth, and all are
the same cutting length or size, and it is not backed by a taper strip to give
the effect of increasing tooth sizes, it is a saw and not a broach. It might
be well to state here, that the common file is also in the saw class.
Sometimes in cutting slots or certain shapes to a shoulder, it is impossible
to use a single broach with a number of teeth, and it becomes necessary to
employ several tools carried in a turret or otherwise, each successive cutter
having the proper shape and the correct increase in size, to produce finally
the finished hole. This also is broaching, as the different cutters represent
the successive teeth of a single broach, which would be employed did not the
shoulder prevent.
2 BROACHES AND BROACHING
Almost innumerable examples might be cited, but these are sufficient,
and taking the various factors into consideration, the following definition
seems to cover the case: Broaching is the working out of holes or slots, or the
machining of surfaces, by tools having a number of successive culting teeth of
increasing size, no matter whether these teeth are arranged singly or in multiple.
THE USES OF BROACHING TOOLS
Originally broaches were principally used to finish square holes, round
holes and keyways. Then gradually they began to be used for splines,
irregular-shaped holes, internal gears and numerous other applications of
internal finishing. Later external broaching was used for a variety of work,
though so far it is used very little in comparison to internal broaching.
No other machine-shop operation has relatively extended so rapidly in
use during the last few years as broaching. Only a little while ago, it was
looked upon as a very special method of machining. It was not considered
in the same class as the then common operations. But this has been changed
with surprising rapidity. -
The tremendous improvements made on broaching machines and broach-
ing tools, are largely the direct result of many years of experience and effort
on the part of a small group of men who will be given their proper share of
credit farther along in this book. The improvements made have greatly
cheapened the cost of production in broaching various kinds of work. It is
remarkable how interesting the proposition has grown since it has become so
specialized. Broaching is now at a point where it is considered indispensable
on certain classes of work.
One great advantage of broaching as a means of finishing certain parts,
over machining by any other method, is that the action of the broach itself
serves as a clamping medium and often nothing else is needed to hold the
work in place, it being slipped on the work bushing or broach shank in a
loose manner according to the work to be done. The work then becomes
fastened in its proper position as soon as the machine is started. This
single item is of great importance in many cases where the chucking of an
irregular piece, in order to finish it by boring or reaming, would be extremely
difficult. In a great many cases the operation of broaching may be finished
in the time ordinarily taken to chuck the piece. In the case of an ordinary
keyway, for instance, no clamps or setting devices are needed other than a
guide bushing and in many instances this is dispensed with. As a rule the
keyway is finished in one operation and but I min. of time is consumed.
Sometimes three or four pieces can be done in one operation, thus increasing
the usual output that many times.
For broaching square holes or other shapes, when the part is not over 2 in.
long, the work can usually be done in one operation, or in from 1 to 2% min.
Longer pieces will usually require the passage of two or more broaches, the
time being increased correspondingly.
BROACHING AND BROACHING TOOLS 3
Another great advantage of the broaching method is the fact that there
is so little resulting scrap. One large automobile factory, which was prob-
ably the first to use broaching to any extent, kept account of Io, ooo pieces
FIG. I.-Examples of broached work.
of all kinds, and found that less than 1 per cent. were spoiled in the process,
a record not approached by any other method of machining. Nor is the
expense of making broaches and maintaining sizes at all excessive, when the

BROACHES AND BROACHING
Fig. 2.-More examples of broaching.

BROACHING AND BROACHING TOOLS 5
tools are properly made, and judged by the accurate and quick results
obtained on the work, they are extremely economical tools for the work to
which they are suited.
A few of the more common examples of broaching work are shown in
Figs. I and 2. These represent pieces being broached daily in scores of shops
in all parts of the country. Some of these pieces will be taken up in detail
later. Other pieces more difficult or especially interesting for various reasons
will also be shown and described together with the machines and broaches
used in each case.
TYPES OF BROACHES
In Figs. 3 and 4 are shown some of the varieties of broaches for internal
work. A majority of those shown are of the pull type, though a few of the
push type are shown in Fig. 4. In a general way the push broaches are
shorter and heavier than the pull type, though they both have many charac-
teristics in common. As a rule the push type of broach is used in a hydraulic
press, though a crank, screw or hand press is often used. The pull type of
broach is commonly used in a regular broaching machine, built especially
for the purpose and unsuited to any other use. Shapers, planers, or other
machines are sometimes fitted up for doing special broaching jobs where no
regular machine is available. Various examples of all of these regular and
special machines will be shown as we proceed. In the number of broaches
illustrated are round, square, rectangular, spline, single keyway, double
keyway, burnishing, three-step, inserted tooth and other types.
The teeth of a broach of either type may be solid or inserted according to
size and uses. The teeth on round broaches may be either cut in spirals,
Something like a thread, or as usual with circular teeth having the edges par-
allel to each other. Rectangular broaches may have the teeth cut straight
across or diagonally, the latter giving a beautifully shearing cut on certain
kinds of steel or other metal. The spacing or pitch of the broach teeth may
be even, or cut differentially in order to eliminate chatter, as in the common
reamer. Broaches are also made for cutting helical grooves of various
kinds. All these, and many more, will be taken up in their proper order and
Specific directions given for their design, manufacture, use and care. Before
proceeding farther, however, the various types of standard broaching
machines will be taken up, and the principal types and makes described in
detail.
BROACHES AND BROACHING
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FIG, 3–Typical examples of pull broaches.


BROACHING AND BROACHING TOOLS
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Fig. 4-Examples of both push and pull broaches.

CHAPTER II
STANDARD TYPES OF BROACHING MACHINES
In classifying the machines described in this chapter as standard ma-
chines, we mean those that are manufactured expressly for broaching work
and as such put on the open market. Strictly speaking, the machines of the
pull, or draw type, are the only ones that can be classed alone as broaching
machines since they are unsuitable for other work. However, several ma-
chines generally used for push broaching are included even though they may
be used for a large variety of other work besides broaching. Allusion is
here made to vertical hydraulic presses, or presses of that class, which are
Commonly used for push broaching work, yet are adapted to other work with
no alterations in the machines themselves. No attempt will be made to
make the list of machines of all types complete, as that will be left to the
catalogs of the various makers, but enough will be shown to cover the better-
known and more commonly used machines as they are found today. A few
machines not included in this chapter may be found in the following chapters
illustrating actual shop operations.
THE PULL TYPE OF MACHINE
The pull type of machine is divided into two general classes: First, those
in which the drawhead is operated by means of a screw; and Second, those
in which the drawhead is operated by means of a rack and pinion. Those
of the first class are far more numerous and will be shown and described
before the others.
The machine shown in Fig. 5 may be taken as a representative Specimen
of the belt-drive, screw-operated broaching machine. It is made by the
J. N. Lapointe Co., New London, Conn. This company builds broaching
machines of various sizes, single and double screw and motor and belt drive.
The Smallest machine they make weighs approximately 445 lb. and has a
Capacity to cut a keyway 94 in. wide and of a reasonable length, and it will
broach a hole J/3 in. square and I in. long. The stroke of this Small machine
is 21 in. The machine shown in Fig. 5 weighs approximately 3750 lb. The
driving pulley is 4% by 22 in. ; size of driving screw, 334 in. in diameter;
I-in. pitch; stroke, 64 in. ; travel of draw head when on low gear, 3 ft. per min. ;
travel of head when on high gear, 5 ft. per min. ; capacity to cut from the
smallest to the largest work practical to broach.
This machine has two positive geared speeds, suitable for light and heavy
8
STANDARD TYPES OF BROACHING MACHINES Q
work; driving nut can be removed for replacement in 20 min., has large ball-
bearing thrust taking all pressure and avoiding heating under heavy broach-
|
FIG. 5.--Typical screw-operated pull broaching machine.
ing cuts. The gears are self-lubricating, running in oil cases; driving screw
is protected from dust and injury by a telescoping tube in rear of machine.
Fig. 6.-Pull type of machine fitted for outboard broach support.
Provision is made for attaching special fixtures on the front end not necessi-
tating extra length broaches.
The machine shown in Fig. 6 is also made by the same company and


IO BROACHES AND BROACHING
along practically the same lines as the one just described except it is made to
be fitted with a chip pan, such as shown under it. This chip pan carries a
Fig. 8-Double head machine with outboard broach supports.
sliding broach support, which is a very valuable feature on some classes of
work where the end of the broach needs support. Otherwise the weight of

STANDARD TYPES OF BROACHING MACHINES
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I2 BROACHES AND BROACHING
a long broach would have a tendency to cut downward and make an untrue
hole.
FIG. Io-Machine with self-sustained broach support.
A somewhat similar machine, but built with double screws and draw-
heads, is shown in Fig. 7. This machine is intended for shops having a
large quantity of duplicate work to do. When this machine is in operation,
º
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FIG. II.-Close up view of heavy broach supported on guides.
one head is on the cutting stroke and the other on the return. The returning
broach can be disconnected, cleaned up and prepared to operate on another
piece by the time the other head has neared the end of its travel. The






STANDARD TYPES OF BROACHING MACHINES I 3
machine is so arranged that one screw may be disengaged, making it a single-
Screw machine when desired. The large size of this machine weighs 48oo lb.,
has a low and high speed of head travel of 3 ft. and 6 ft. per min. respectively.
The screws are 234-in. in diameter, 2-in. pitch, 54-in. stroke. Capacity of
machine up to 3-in. Square holes. Floor space, 3 by 16 ft.
Fig. 8 shows one of these double-head machines fitted with a pan carrying
slides and broach guide supports similar to the one shown with the single-
head machine. All of these machines are also supplied with pumps and hose
for flooding the work.
A machine built on lines of approved broaching practice by the Lapointe
Machine Tool Co., Hudson, Mass., is shown in Fig. 9. It is motor-driven
though this company furnishes either belt or motor drive. This particular
machine weighs 2300 lb., has a capacity to cut keyways up to 1% in. wide or
broach square holes up to 3 in. across flats from a drilled hole in steel. The
stroke is 50 in. ; driving screw is 234 in. in diameter, I}% threads per in. ;
Cutting Speed, 48 in. per min. ; return Speed, 225 in. per min. ; floor space, to
allow for Screw travel and broach, 15 in. by 31 ft.; motor required, 5 hp.
Oil pump and other necessary equipment is furnished.
A machine of the same class, except belt drive, built by the same firm, is
shown in Fig. Io. This machine has a sliding broach support attached.
This support is on the same principle as the one previously described, except
that it is self-supporting and does not depend from the draw-head bracket.
A close-up view of this machine, showing a heavy internal gear broach
in place, is shown in Fig. II. This at once explains to the practical man
the advantage of such a support for heavy tools. These supports are fur-
nished to be fitted to the various sizes of machines made by this concern.
While the general looks of these machines do not differ materially, the
sizes differ considerably, one of the larger models weighing 4900 lb. and
having a screw 3% in. in diameter and a 60-in. stroke, with a capacity for
keyways 4 in. wide, or for holes 4 in. across the flats from a drilled hole in
steel. The motor for this size machine is a 10-hp. and the floor space 54 by
226 in.
MACHINES OF THE RACK-AND-PINION CLASS
A machine typical of those using a rack in place of a screw to operate
the draw head, and known as the Knowles type, is shown in Fig. 12. This
machine is made by the Pawtucket Mfg. Co., Pawtucket, R. I. Two sizes
of this machine are made, weighing respectively 1325 and 2450 lb. The
smaller machine will broach keyways up to 5s by 916 in., 6 in. long; its
cutter is 28% in. long and the bar 49% in.; extreme length of bed, 63 in. ;
width of rack, 2% in. ; length of stroke, 42 in. ; standard speed of cutter
bar, 7 ft. 4 in. per min. ; floor space, allowing for bar and all, II ft. 5 in. by
3 ft. 2 in. The larger machine will broach keyways I by }.3 in. by 12 in. long;
extreme length of bed, 98 in. ; width of rack, 6 in.; hole in head, I 1316 in. ;
14
BROACHES AND BROACHING

STANDARD TYPES OF BROACHING MACHINES I5
stroke, 59 in...; speed of cutter bar, 4 ft 6in. per min.; floor space, 16 ft 6in,
by 3 ft. To in. When using these machines on steel an oiling attachment
is used. These machines may be used for practically the same line of
work as the screw-operated type, up to the limit of their capacity. As a
rule, however, these machines are generally used for keyseating and work
of that character rather than for the more complicated class of broaching.
The machine shown is used in the shop of the New York Air Brake Co. for
broaching valve seats and some of the special broaches used are shown on
the rack at the left.
The broaching machine shown in Fig. 13, made by John T. Burr & Son
Brooklyn, N. Y., is primarily a keyway cutter. The model shown is known
FIG. I.3.−The Burr keyway broaching machine.
as their No. 4 Keyway Broaching Machine, and is of the rack-and-pinion
type. The main boxes and face plate are tied together by a pair of distance
rods, providing ample strength to resist the strains of broaching. The
driving pulley is 20 in. in diameter for a 4-in. belt. The machine may be
started, stopped or reversed at any point of its travel. Either straight or
taper keyways are cut with equal facility by a single pass of the cutter, in
from to to 20 sec. The largest keyway that can be cut is 33 by 916 by 6 in.,
and the weight is about 2000 lb.
The broaches used are of rectangular section, which reduces the bushings
to the most inexpensive form. These bushings are simply round stock the
size of the bore to be keyseated, channeled out to allow the broach to be

I 6 BROACHES AND BROACHING
drawn freely through. The channel is made deep enough for the insertion
of either a straight or a taper bearing strip, so that both straight and taper
keyways may be cut by using the same bushing with different bearing strips.
The foregoing four makes of machines cover the present-day field
the pull-broaching line as far as the public market is concerned. Other
makes will be described later, but they are not machines that are on the
open market.
Wherever the length of stroke is mentioned on any of these machines of
either type, the maximum is meant, as all are adjustable to suit the work
in hand.
MACHINES FOR PUSH BROACHING
Several classes of machines are used for push-broaching work. All of
the standard ones are of the vertical type, as those for pull broaching are of
the horizontal type, though exceptions may be found to both in special-built
machines. In the vertical push-broaching machines are found hydraulic,
Screw, rack, Crank and hand-operated lever machines. The hydraulic
machines are far more commonly used than any other for push-broaching
work, but most drawing presses are capable of being used for push-broaching
work under favorable circumstances. Sometimes the ordinary punch
press is used for broaching work of a limited nature. The well-known
hand-operated mandrel presses are also frequently used for Small amounts
of light broaching work. No attempt will be made to cover the entire field
of push-broaching machines, but a few of the better-known machines will
be illustrated and described to give the reader an idea of the classes, range
and capacities.
HYDRAULIC-OPERATED MACHINES
The press shown in Fig. 14 is but one of a number of models made by
the Watson-Stillman Co., New York City. The particular machine shown
has a capacity of Io tons, and weighs about 1650 lb. It was designed for
broaching small holes in automobile parts and for miscellaneous work in
machine shops. The pump, which is mounted on top of the press, has three
pistons 134 in. in diameter and of 194-in. stroke. The ram is double-acting
and is 6 in. in diameter with piston areas proportioned to cause it to move
down at the rate of 35 in. per min. and up Ioo in. per min, when the shaft
makes Too r.p.m. Its motion, which is 12 in., is controlled by a special
valve actuated by a lever. When the lever is in its central position the
valve causes the water to circulate without disturbing the position of the
ram. On moving the valve to one end the ram is forced downward, when
moved to the other end the ram is raised.
The platen is 12 by 18 in. inside of the rods; the maximum vertical
opening is 18 in. ; the height from floor to face of lower platen is about 31 in...;
the pulleys are 24 by 4 in., and the press as shown is 8 ft. 8 in. high.
STANDARD TYPES OF BROACHING MACHINES
17
Fig. 14-Watson-Stillman hydraulic broaching press.

18
BROACHES AND BROACHING
*Fig. 15.-Press made by Hydraulic Press Mfg. Co.

STANDARD TYPES OF BROACHING MACHINES I9
This press is modified to suit requirements, and the company also
makes other models, suitable for broaching work, up to 150 tons capacity,
ºr more.
FIG, 16,-75-ton, self-contained broaching press.
The press shown in Fig. 15 is very similar to the one just described. It
is made by the Hydraulic Press Mfg. Co., Mt. Gilead, Ohio. This company
builds various models of broaching presses. In this machine, which is known
as their No. 8 press, the ram is counterbalanced so that it can be run down to

2O BROACHES AND BROACHING
the work quickly and returned by the hand windlass attachment. The
wood-lined box below catches the broach without injury as it drops after
completing the operation. The specifications are: Diameter of ram, &
pressure capacity, 63 tons; size of platen, 24 by 24 in.; daylight space, 36 in...;
run of ram, 24 in. It is operated from an accumulator or by a pump sepa-
rate from the press, or by one mounted on it. A two-rod press of this type,
but of 15 tons capacity, known as a No. 4, is also made. The various dimen-
sions of this latter machine are approximately half those of the former.
Another machine built by the same firm is shown in Fig. 16. This is a
self-contained machine with both motor and pump mounted on an extended
base which is attached to one side of the press. It is suitable for the wide
range of broaching and forcing work coming up in machine and automobile
shops. The ram is counterbalanced and is controlled by a hand windlass
operating with slight effort on the part of the operator. The ram can thus
be raised or lowered to admit various sizes of work. When the ram is moved
downward by the hand windlass the cylinder is filled with water by the vac-
uum which is caused by the ram's downward movement. By this action
the pressure upon the broach or the material in the press is initiated as Soon
as the motor and pump are started.
The ram is fitted for extension blocks which may vary in shape or length
according to the size of the pressing surface, or the height of the daylight
Space.
The ram of this press is operated by a two-plunger horizontal pump,
having plunger diameters which if desired may vary from 9% to I in. but all
having a stroke of 3% in. The pump is equipped with an automatic knock-
out attachment which limits the pressure to predetermined maximum point.
This may be any pressure which the material requires within the maximum
rated capacity of the press. All parts of the pump are easily accessible,
thus eliminating difficulty in making adjustments and repacking the pump
plungers. The pump shown in the accompanying illustration has a single
reduction of gears. It may, however, be equipped with a double reduction
should it be desired. The motor and starting rheostat are conveniently
located, being within the easy reach of the press operator. A motor of 2-hp.
capacity is required.
The Speed at which this press may be operated varies with the plunger
diameters of the pump. The larger the pump plungers the more rapid will
be the movement of the ram, more water being forced into the cylinder at
one stroke of the pump.
The press as shown in the illustration has a Io-in. ram upon which can be
initiated a maximum pressure capacity of 75 tons. The entire press proper
is of steel construction, the beams being formed by steel lugs cast on the cylin-
der while the sills are formed by steel lugs cast on the base plate. Bright
Cold-rolled steel shafting is used for the strain rods.
The two brackets which form the pump base are cast iron and are bolted
STANDARD TYPES OF BROACHING MACHINES
2I
Fig. 17-35-ton Metalwood press,

22 BROACHES AND BROACHING
securely to the main part of the press. Bolts are used here because it is
sometimes desirable to operate the press from an independent pump or an
accumulator system. The motor base in this case is omitted.
Fig. 18.-A Io-ton light broaching press.
The daylight or stock space of this press is 18 in with a 12-in, run of ram.
The press bed or pressing surface is 24 in square. The press bed has an
opening directly under the ram to receive the broach as it passes through

STANDARD TYPES OF BROACHING MACHINES 23
the work. A wooden box receives it as it drops. The extreme height of the
press is 6 ft. 4 in. .
A press made by the Metalwood Mfg. Co., Detroit, Mich., is shown in
Fig. 17. This machine has an adjustable safety valve for the pump to pre-
vent overload, or it can be adjusted to a predetermined pressure. The pump
is controlled by a Metalwood single-lever quick-operating valve, giving
control of speed of ram, pressure applied and return of ram. Ram is returned
automatically at any predetermined stroke. All hydraulic connections are
of seamless steel tubing and drop-forged steel fittings. It is equipped with a
gage reading in pounds per square inch and tons applied on ram or work.
The principal specifications are: Ram, 4% in. in diameter; stroke, maxi-
mum, 30 in.; cutting speed, 4% ft. per min.; pull-back, weighted; distance
between columns, 23% in. ; distance between ram and platen, 44 in...; platen
to floor, 31 in.; hole in platen, 4 in...; height overall, Io ft. 6 in...; floor Space,
32 by 39 in.; weight, 3200 lb.; pressure capacity, 35 tons.
A smaller-size press, also built by the Metalwood company, is shown in
Fig. 18. This is a very convenient size for certain kinds of work. The
machines are made in Io, 15 and 20 tons capacity. An air pull-back oper-
ating at Ioo lb. pressure insures quick action, the operation being controlled
by the lever shown at the right. The ram stroke on the three sizes respec-
tively is 6, 6 and 18 in. and work 9, 9 and 15 in. in diameter is taken. The
weights are 9oo, I4oo and 3200 lb.
A SCREW-OPERATED WERTICAL PRESS
The broaching press shown in Fig. 19 is a vertical screw-operated machine
made by the Standard Machinery Co., Providence, R. I. It has a variable
stroke mechanism which can be adjusted to operate through any intermediate
distance between the extremes. The large screw operates the ram or slide,
the speed of which can be varied by changing the gear ratio on top of the
machine, or by giving the drive belt a different speed. The ram has a con-
stant speed throughout the stroke. A quick return and an automatic stop
are provided. Two sizes of this machine are built, the larger requiring
about 10 hp. The capacities and specifications of these two sizes are 20
and 40 tons; stroke, 7 and 12 in. ; diameter of screw, 2% and 4% in.;
pitch (double) 94 and 1 in. (single); height overall, 6 ft. 2 in. and 7 ft. 9 in.;
work space, 13 by 15 in. by Io in. high and 16 by 19 in. by Io in. high; weight
2Ooo and 5200 lb.
A HAND-OPERATED PRESS
The hand press, Fig. 20, made by the Atlas Press Co., Kalamazoo, Mich.,
may be taken as typical of presses of this class. It is suitable for numerous
broaching jobs, which will be elaborated upon later. This press may be
used mounted upon a base as shown, upon a bench or upon some other
24 BROACHES AND BROACHING
machine, such as the end of a lathe bed. The pinions on these presses are
made of chrome-vanadium steel forgings. The rams are of high-carbon
nickel steel. It will take work up to 20 in in diameter; has a capacity over
Fig. 19.-Screw-operated vertical broaching press.
table of 18 in.; ram is 2 by 2 in. by 24 in long; floor space of pedestal, 22 by
29 in.; weight of pedestal, 375 lb.; weight of head, 550 lb.; leverage, 16o
to 1; capacity, Io tons pressure. This press is known as their No. 3, but a
number of others suitable for broaching work are also made.

STANDARD Types of BROACHING MACHINES
25
FIG. 20,-Atlas hand-operated broaching press,

CHAPTER III
EXAMPLES OF PULL-BROACHING WORK AND PRACTICE
The simplest and most common broaching work is that of cutting key-
ways. For this the pull broach is practically in a class by itself, though in
Some cases push broaches are used. For gears, cams, flywheels, sleeves,
levers and the like, where keyways are to be cut in considerable numbers,
no other method can compare with broaching in speed, accuracy or economy.
Only on Small quantities or unusual sizes of work are other methods prefer-
able. The time taken to broach out a keyway, of course, varies with the size
and length of the keyway and the metal being broached. As a general rule,
any ordinary keyway may be broached at one pass with a single broach,
though occasionally two or more broaches have to be used; especially is
this true if the keyway is of unusual size and the metal tough. Where the
work is comparatively thin, several pieces are often broached at once with
One pass of the tool. The shape of a piece, however, does not always lend
itself to this. *
A good example of keyway broaching is done on Ford automobile wheel
hubs. Keyways 34 by }% in. and 3% in. long in a tapered hole are cut on
a Lapointe machine at the rate of Ioo per hr. Another case where key-
ways 916 in. wide by 962 in. deep, and 4 in. long were cut in steel, the time
required was less than a minute, which included the cutting and the placing
and removal of the piece. s
For ordinary keyway cutting, only a work bushing, which also is a guide
for the broach, is used to hold and locate the piece. The action of the
broach as it is drawn in serves to hold the work securely in place on the
bushing and against the face-plate of the machine. As soon as the broach
has finished cutting the work is simply pulled off by the operator. The
broach is then run out to starting position and another piece placed on the
work bushing ready for the next cut.
The machine shown in Fig. 21 gives a good illustration of common key-
way work. The piece shown in the machine is a long sleeved gear but the
method of locating and holding the work is exactly the same as used for
work not so long. Other examples of work are shown just in front of the
machine and as all are bored the same size and all have the same-sized key-
way broached in them, the same work bushing and broach does for all. The
steel sleeve A 13 in. long, is having a 93-in. keyway 94 in. deep broached
in it at the rate of 15 per hour.
Double-opposed keyways are cut with the same facility as are single
26
PULL-BROACHING WORK AND PRACTICE 27
ones, only a different form of work bushing or guide is used. As a general
rule a double-opposed keyway broach has a tongue or guide running along
its length on one side halfway between the rows of teeth, as shown in Fig.
4, Chapter I. This tongue fits a groove in the split work bushing or broach
Fig. 21.-Machine set up for broaching keyways.
guide and keeps the broach cutting evenly on both edges as it is drawn
through the work. In other cases, however, where the work will permit,
the body of the broach is made to fit the bore of the work and no work bushing
is used, the piece being butted against the face-plate or the end of the broach

28 BROACHES AND BROACHING
guide. This same plan of having the body of the broach fit the bore of the
work is also sometimes used for single keyways.
Where two keyways of the same size are to be cut at right angles to each
other, or quartering, it is common practice to cut the keyways in two opera-
tions with the same broach. For this purpose a work bushing slotted to
correspond to the positions of the keyways is used. The work is put on and
one keyway cut, then this keyway is moved around to coincide with the
quartering slot of the bushing. A slightly tapered piece is then forced into
the groove and keyway, locking the work into position for the next keyway.
An illustration of this type of bushing is shown in the section on work holders.
Another and better way where the quantity of work will warrant, is to
use a broach with two cutter bars. In this way the two keyways can be
FIG. 22.-Broaching machine made from a lathe.
cut as quickly as one. This also holds true where more than two keyways
are to be cut as broaches can be had with multiple cutters.
Still another way is to use an indexing fixture on the face-plate to hold
the work, using a single cutter bar. This method is of course slower, but
has the advantage of being adapted to various jobs where quantity is not
the main object.
BROACHING MACHINE MADE FROM A LATHE
To show that good work may be done on a home made machine a broach-
ing machine used in the shop of the Salem IronWorks, Winston-Salem, N.C.,
is shown in Fig. 22.
An old lathe, with a lead screw in the center of the bed, has been converted
into a draw broaching machine by planing off the V's and fitting it up as

PULL-BROACHING WORK AND PRACTICE 29
shown. A heavy cast-iron bracket A has been bolted to the end to hold
the work bushings. The sleeve of this bracket is split so that work bushings
of different sizes can be easily clamped in place. The engraving shows a
large drum in position for broaching out the keyway. The drawhead B
consists of a cast-iron plate channeled to slide on the planed top of the lathe
FIG. 23.-View of screw drive gears.
bed, having a nut underneath to fit the lead screw and a bracket on top to
hold the end of the broach shank.
Different drawing speeds may be obtained by shifting the drive belt on
the cone pulley, as well as by using the regular back gears, making six possible
Fig. 24.—Two of the keyway broaches and bushings.
changes in all. The fact that keyways in both iron and steel castings are
broached in this machine, makes the speed changes particularly convenient.
A better idea of the way the lead screw is driven from the spindle will
be obtained from Fig. 23. A heavy pinion A is keyed to the rear end of the


3O BROACHES AND BROACHING
spindle, and this meshes with a heavy gear B on the lead Screw; the ratio
being about 2% to I.
The broaches used to cut the keyways are made of a bar of rectangular
tool steel, in which the teeth are cut, set into a bar of machine steel. Two of
these broaches and work bushings are shown in Fig. 24. The bars of the
broaches are 6% ft. long and the cutters extend 3 ft. The teeth are I-in.
pitch and increase in length 362 in. to the foot, or approximately 2% thou-
Sandths each.
A BURTON KEYWAY MACHINE
The machine shown in Fig. 25 was made by the Burton Machine Co.,
Erie, Pa., and is the only one of this make the writer ever saw. It was in
use in a shop visited in Canton, Ohio. It differs in many ways from others.
It has two drawscrews geared together and set parallel with each other. The
drawnut is made up of two half nuts set back to back and running between
the two drawscrews. The drawbar or head to which the keyway cutter bar
is attached, is drawn back between the two screws as the cut proceeds.
Means are provided for automatically stopping or reversing the stroke. The
work to be keywayed is set over a cone-shaped holder and is locked in place
by means of a sliding block shown at the extreme right. This block slides
on the bar shown which is notched on the side for a pawl carried on one side
of the block. The machine complete probably weighed about 500 or 600 lb.
CUTTING A KEYWAY IN A TAPER HOLE
The method of holding the steering spindles of an automobile, while
cutting a keyway in a taper hole in it, is shown in Fig. 26. A wedge-shaped
plate, fastened to the front of the Lapointe broaching machine, has pins in
it to locate the end of the spindle correctly when the taper hole is placed over
the work bushing. The slant of this plate is just right to bring the upper
part of the taper hole parallel with the travel of the broach when the spindle
is set as shown. No holding clamps are necessary, as the draw of the broach
holds the work securely. The two pins shown at the upper left-hand corner
of the plate are used to locate the mate of the spindle forging being broached,
as they are made right- and left-hand.
In connection with keyway broaching it may be well to state here that
dovetail slots or keyways may be broached just as easily as the ordinary
kind, in either straight or taper holes.
BROACHING SPIRAL KEYWAYS
Spiral keyways or grooves are also cut as easily as any other when once
the machine is fixed for it. In most cases this necessitates the use of a
revolving broach holder as well as a master broach guide grooved to corre-
PULL-BROACHING WORK AND PRACTICE 31
spond to the groove to be cut. In other cases, however, the broach does not
rotate, but instead the work is placed on a revolving work holder or bushing,
Fig. 25.-Burton keyway broaching machine.
*
-
FIG. 26.-Broaching keyway in tapered hole. -
ball bearing or otherwise, so as to rotate according to the spiral of the broach
teeth.


Spiral Keyways
}%2/-A-
//o/aers
% %
Left and Right-Hand Spiral Keyways Spiral Keyway in Tapered Hole
FIG. 27.-Broached spiral keyways.
Aaaayer
km sºme me • * * *
sº
- - - - - -???
YZZZZZZZZZZZZZZZZZZZZZZZZ ZZZZZZZZZZZZZZZ2222222222222
C Sha/7A:
Brooch
FIG. 28.-Fixtures used for broaching spiral keyways,
‘.











PULL-BROACHING WORK AND PRACTICE 33
In an article published in the American Machinist, May 9, 1912, Frank
J. Lapointe Says:
Two 9%-in. spiral keyways in a 194-in. hole are shown in Fig. 27. These pieces
are about 3 in. long, and a production of about 25 to 35 per hour is obtained. The
gears are very accurately broached in regard to the width of the keyway and lead
of the spiral. This is a very high production for Such a piece. There are, no
doubt, many places where similar pieces could, but have not been, used because
the piece was considered too expensive. With the modern broaching machine and
with properly designed broaches, the cost of machining a piece of this nature is
very little indeed.
Two spiral keyways, one left- and one right-hand, are seen. The piece shown
can usually be done in one operation depending upon the length of the work and
material to be cut. It is accomplished by the use of a special double spiral broach
which cuts the two keyways at one stroke of the machine. This assures proper
indexing of the two keyways with relation to each other.
A spiral keyway in a tapered hole is shown. This can also be done in one
operation, and while it is very rare that a keyway of this shape would be called
for, this only gives an illustration of another peculiar piece that can be done with
properly designed broaches. This piece can be broached very accurately as regards
lead of spiral and width of keyway, but there is a slight defect as to the depth owing
to the taper of the hole. This being so slight, in most cases it is negligible.
In the March 16, 1916, issue of the American Machinist, M. Henry
writes:
A job accomplished on a standard type of broaching machine is shown in Fig.
28, the work being small and made in large quantities with two spiral keyways
cut in it. The piece is mounted in the bushing at A, while two broaches are drawn
through it—namely, roughing and finishing. The arrangement of the tools for
this operation is as follows: In the bushing A is placed the guide pin B. The shank
of the broach C, with the work slipped over it, is pushed through the work bushing
and gripped by the pin D in the broach holder E. The work is now held by hand
against the work holder and is prevented from turning by the sides F. The machine
is started and draws the broach through the work, the spiral twist being obtained
as the groove necessarily follows the line of the pin.
As there is no means of allowing the broach to twist in these machines, an
adapter is provided. It consists of the broach holder E in the adapter G, two check
nuts H and a ball bearing J. All these parts are mounted on the drawbar of the
machine in a manner similar to that employed for holding broaches on ordinary
broaching machines.
Fig. 29 is an illustration taken from the catalog of the Lapointe Machine
Tool Co., Hudson, Mass., to show the broaching of four spiral keyways at
once. Two broaches are used, a roughing and a finishing. The roughing
broach is shown in the machine and the finishing broach lying in the pan,
An end view of a piece of the work is shown next to the finishing broach.
BROACHING ROUND HOLES
Next to keyway work, the broaching of round holes is probably the most
familiar to the average machinist. The great variety of work for which it
3
34
BROACHES AND BROACHING
Fig. 29.-Machine set up for broaching four spiral keyways.
Fig. 30.-Finishing a round hole in a steel casting.


PULL-BROACHING WORK AND PRACTICE 35
is adapted is almost unlimited. On some classes of work, round-broaching
is much preferred to finish-reaming. In a large number of ordinary jobs,
the work is drilled close to size and then finished with a single broach. Other
jobs require two or more broaches in order to obtain the required accuracy.
A round-broaching job is shown at A, Fig. 30. This is a steel casting
which is located by means of a small plate screwed to the face plate of the

36 BROACHES AND BROACHING
machine. After a piece is broached it is removed, the broach run out and
disconnected, another piece put in place, the broach run in and Connected
to the drawhead and then the broach is pulled through the hole. The steel
castings were so hard and tough that reamers were of no use at all. The
hole is 1}4 in. in diameter by about 3% in. deep. The broach produces
about 30 per hour.
An unusually heavy broaching job done in the Rudge-Whitworth shops
is shown in Fig. 31. It is especially interesting on account of the size of
the broaches, the method of handling them and the way they are supported
on the overhang. The machine used is a No. 4 Lapointe. The broaches
shown are 434 in. in diameter, and made up of case-hardened steel disks
strung on a specially heat-treated nickel steel bar. By using the chain
hoist and hooks, the operator has little trouble placing or removing the
broaches from the wheeled carriers and then connecting or disconnecting
the drawhead.
BROACHING AND BURNISHING BEARINGS
The method of broaching and burnishing bearings, shown in Fig. 32,
was first obtained in the shop of the Locomobile Co., Bridgeport, Conn.
These bearings are of composition metal and the broach is made to finish
a 1%-in. hole and has 12 teeth which increase in size by o.oOos in. each from
first to last and the swage or burnisher A is o.oos larger than the last tooth
of the broach, being tapered slightly at the start, so that it doesn’t shear the
bearing. The bearings thus finished are very true and do not need to be
touched with reamer or scraper. The lubricant used is prime lard oil and
the engineer's figures show that it takes from 5 to 6 hp. to run the machine
and a pull of 5ooo or 6000 lb. to draw the broach through. The pressure
of the burnishing part of the broach on the bearings is so great that some other
means than the two regulation screws had to be devised to keep the parts
from spreading, which is done by using the jig shown in Fig. 33, which con-
sists of a heavy steel ring or box, into which the end of the connecting rod
is set and the setscrews shown used to keep the bearing caps from being
forced apart. This jig, of course, rests against the head of the broaching
machine when in use, as shown in the first halftone.
ANOTHER BEARING BROACH
The broaches shown in Fig. 34 were made for the Marathon Motor
Works, Nashville, Tenn., by the Lapointe Machine Tool Co. The white
bronze bearings of the connecting rods and the disk A are broached with
these tools. The blank spaces between the teeth both compress the metal
and act as truing guides for the cutting teeth. The spiral grooves assist
in keeping the parts lubricated during the process, lard oil being used. There
PULL-BROACHING WORK AND PRACTICE 37
is about ooro in difference in size from one end of the broach to the other.
The blank spaces are slightly tapered on the entering end to prevent bunging
up the metal of the bearing on the draw. These broaches do entirely
FIG. 32.-A sizing and burnishing broach.
away with reaming and are much faster working and give just as good results
for when finishing a hole by reaming, the cutting edge of each reamer blade
FIG. 33.-Holder used to prevent spreading.
travels a distance approximately equal to the circumference of the hole
multiplied by the number of turns made by the reamer in passing through
the work. In the case of a round broach, the distance traversed by any


38 BROACHES AND BROACHING
point on the broach in machining a hole is equal to the length of the work;
hence, it can easily be seen that broaching is a much faster operation than
reaming, especially when the broach has a cutting speed of at least 4 ft.
per min.; moreover, the broach will maintain its size for a longer period than
a solid reamer, because the finishing end of the broach has a number of
teeth of the same diameter, and as these only take very light finishing cuts

PULL-BROACHING WORK AND PRACTICE 39
they are subjected to very little wear. Even an adjustable reamer has no
longer life than a well-made round broach.
It has been demonstrated that the broaching of hard chrome-nickel
Steel, such as is used in automobile work, is a much cheaper process than
reaming. A typical job is shown in Fig. 35, which illustrates two connecting-
rods and their broaching fixture. The small end of one rod and the large
end of the other are broached simultaneously on a regular No. 3, Lapointe
machine. In this way, one complete rod is finished for every stroke of
the machine. The fixture is not absolutely necessary, but adds consider-
ably to the production. These connecting-rods are first drilled to the size
of the broach shank or to a diameter of from o.o.15 to o.o.30 in. under the
required size. They are then finished by broaching, thus eliminating both
machine and hand-reaming. After the rods have been broached, the large end
is split and the lining bushing for the large end is inserted. The bushing
for the small end is pressed into the rod. These bearings or bushings are
then broached, and the finish obtained can only be duplicated by scraping,
although broaching is, of course, much cheaper, and the metal is com-
pressed somewhat, thus giving the bearing a hard, glazed surface that resists
Wear.
The broaches used on this work are of the same type as those shown in
Fig. 34 and are made up with plain round sections for the purpose of keeping
the broach from “running” or “crawling,” as it is essential that the center-
to-center distance of these rods be kept fairly accurate. By introducing
plain blanks or sections between the teeth, the broach is kept properly
aligned with the hole, because there is always some portion of the blank
Section in the work while some of the teeth are cutting.
When using these broaches in cast iron, a soap cutting compound is
used, as this gives the broached surface a highly polished finish. For chrome-
nickel steel, a good grade of cutting oil will give satisfactory results. On
Some work, no drilling whatever is done prior to broaching, and very often
only one broach is used; but if the work is longer than, Say 2 in., a roughing
broach usually precedes the finishing broach. Of course, broaching from
the rough can only be done when the broaching operation comes first, as
otherwise the broach would follow the rough hole and, consequently, the
finished hole would be out of true with any other surfaces which might be
machined before broaching.
In discussing the broaching of bronze castings in their shop in Hudson,
Mass., Frank J. Lapointe says: These castings have a round hole 2 in. in
diameter and 4% in. long. We allow %-in. Stock to be removed, or 316
in. on a side, the hole being cored 3% in. Smaller than the finished size.
When we bored and reamed these, we allowed 94 in. and the time was about
Io min. each. We broach them in I}4 min. and do not have to bother to
clamp or chuck the work in any way. The finish is better than by ream-
ing. In reaming hard bronze it is difficult to overcome the chattering
4O BROACHES AND BROACHING
and waving of the reamer, but the broach properly made does away with
this difficulty. Of course the results obtained by broaching depend on the
broach itself. Our broaches are ground all over after hardening and are
backed off at the proper angle to give them a nice cutting edge. The teeth
are nicked to break the chips on the heavy cutting part of the broach, but
the last six or eight teeth that do the sizing are not nicked. Following the
last six or eight sizing teeth is a short pilot which supports and guides the
broach. One very important thing in broaching round holes is the proper
spacing of the broach teeth. At no time must there be less than three teeth
in the work, in order to properly support the broach; if the teeth were so
Coarse that only one tooth was cutting while another was entering, it would
give the broach a slight movement, causing waves in the work. The broach
must always be made up with differential spacing of the teeth. If the teeth
are all evenly spaced, as a rule very unsatisfactory results will be obtained.
When making broaches a number of things must be taken into considera-
tion, viz., material to be cut, length of work, amount of stock to be removed
On the outside, and the shape of the work, so that the proper support can be
provided. The length of the broach depends entirely on the metal to be
removed. Of Course in cases where the broaching operation is for sizing, a
short broach is used, usually having about Io in. of cutting edge. If the
broach is to remove 96 in. of stock, the length may vary from 28 to 40 in.,
depending on the length of the work.
The use of four broaches at once on a J. N. Lapointe two-spindle machine
is shown in Fig. 36. The broaches used were made by the H. J. Walker Co.,
Cleveland, out of carbon steel, and were hardened by the Vincent Steel
Process Co., Detroit, Mich. The holes finished are 2316 in. in diameter
and 6oo pieces are finished per day. It is claimed that these broaches have
the speed and nearly the length of life of those made of high-speed steel.
BROACHING SQUARE HOLES
To the man doing broaching work there is more than one kind of “square”
hole. There is the square hole with round corners but straight sides; the
hole with round corners and the sides only partly straight, as the round of
the drilled or reamed hole is not entirely cut away; and other variations of
these; and last and most rare, the perfectly squared hole, with sharp Corners.
For commercial purposes, the hole with fairly well cleaned-up sides and
round corners is plenty good enough as a rule, and usually can be finished
from the drilled hole at one pass, in almost any grade of metal.
A bevel gear blank being broached out is shown in Fig. 37. This is done
in the shop of Brown & Sharpe on a Knowles type of machine. The metal
is a particularly tough grade and several broaches are used to obtain the
finish and accuracy needed for their work. The blank is located on the
face-plate by means of a ring and is held securely in place by two strap
PULL-BROACHING WORK AND PRACTICE 4 I
clamps as shown. Speed is not sought after in this case as accuracy is the
principal aim.
FIG. 37.-Broaching a square hole in gear blank.
BROACHING TAPERED SQUARE HOLES
In broaching tapered square holes, a broach like the one indicated in
Fig. 38 is used, and one corner broached at a time. After one corner is

WoRK Bushing
CuTTER BAR
A
section at A B
Fig. 38.-Sectional view of cutter bar in work bushing and shape of tapered square hole when finished.
FIG. 39A.-Broaching square holes in jig. Fig. 39B.-Broach, holder and cutter.
t







PULL-BROACHING WORK AND PRACTICE 43
broached, the work is indexed a quarter turn and the next corner is broached.
The work bushing as shown is tilted according to the taper of the hole being
broached, in practically the same way as for broaching a keyway in a tapered
hole, which has already been described. In no way, other than by broaching,
Could holes of this character be machined on an economical commercial basis,
and accurate results be obtained.
BROACHING SQUARE HOLES IN A JIG
In a short article in the American Machinist, T. B. Greene says:
An interesting operation is shown in Fig. 39.4. It consists of a motor-car hub
detail in the shape of a flange 316 in. thick with six 716 in. holes, which have to
be squared out to o,468 in. The centers of the holes have to be kept good, so
that a jig is necessary for the broaching operation which follows the jig-drilling
operation.
The jig consists of a cast-iron plate bored to receive the check on the hub
flange and also to take an adapter, fitting the machine table. These holes are
bored to correct centers. Six holes are drilled and counterbored in the plate with
the same centers and spacing as the work. This is to allow the passage of the broach
and also to give clearance for burrs thrown up on the back of the hole after
broaching. -
The broach holder in the machine is set true with the holes in the jig by means of
a test bar, and the work is brought into alignment by the plain guide on the broach.
The broach is made of a special steel, which lends itself to straightening easily
after hardening, and is ground all over.
The teeth are 964 pitch and remove about o.o.o.2 in. per tooth. Two flats are
milled on the shank of the broach to take a U-shaped cotter for pulling purposes,
as shown in Fig. 39B. These flats are in correct relation to the sides of the broach,
so that it may be lined up from the flats to get the sides of the square hole true with
the center line of the work.
The work is turned out at the rate of Io to 12 an hour, i.e., 60 to 7o holes per hour.
Over 2000 holes have been done without the broach requiring sharpening. Roughly
speaking, it is eight times quicker than filing and finishing with a sizing drift, which
was the method used for finishing these holes before broaching was adopted.
BROACHING RECTANGULAR HOLES
The next job shown in Fig. 40, is the broaching out of rectangular holes in
connecting rods. This is representative of work of this class. The holes
broached as shown are 4 by 6 in. and 2 in. thick. The rods are rough drop
forgings and about 25 holes are broached per hour.
In Fig. 41 is shown a No. 4 J. N. Lapointe machine rigged up for broach-
ing out vise bodies. The hole broached is 4% by 6 in. The piece itself
weighs about 90 lb. The broach used in broaching this work weighs 265 lb.
Owing to its enormous weight it is arranged with shank on the rear end to
telescope into the support bracket, which is firmly fastened to the table, so
44 BROACHES ANDIBROACHING
that when the broach is disconnected from the machine, it is supported in
the bracket, and can be conveniently rotated to clean the chips out.
.
-
FIG. 40.-Broaching a connecting rod.
After the vise jaw is slipped on the end of the broach for the operation,
the machine is reversed, bringing the connecting bushing into the broach,
FIG. 41.-Broaching out vise bodies.
and by means of a key the broach is connected, and the machine started for
the operation, and before the shank leaves the support bracket the pressure
is sufficient to hold the broach in position without any further support of the


- PULL-BROACHING WORK AND PRACTICE 45
bracket. This makes the machine very convenient and handy for handling
such heavy broaching tools, and has been found most advantageous.
ANOTHER WISE JOB
The making of the Prentiss bench vise, which has been known to me-
chanics for many years, contains some interesting processes as carried on by
the Bagley & Sewall Co., Watertown, N. Y.
The tools used in broaching the bodies are interesting both on account
of their size and the way in which they are built up. They are shown in
Fig. 42. Arranged on the bench behind the broaching machine are a number
Fig. 42.-A special machine for vise work.
of vise bodies, most of them of the plain solid-jaw type, with the broaches in
place, giving something of an idea of the range of sizes.
The body to be broached is supported on the bracket at the end of the
machine, as shown, this being adjustable for various sizes, so as to easily
bring the work to the proper height. In the larger sizes these broaches are
built up of tool-steel toothed plates, on soft-steel bodies, as can be seen.
It will also be noted that there are small sections inserted on some of the
broaches, on top, just where they leave the work. This is especially notice-
able on the one in the machine. The use of sections inserted like this makes
it easy to keep the corners sharp, as a new piece may be put in or the old



46 BROACHES AND BROACHING
piece sharpened without working over the whole broach. Broken sections
may also be replaced in this way, without making an entirely new plate.
Another interesting feature is the method of locking the broaches to the
draw spindle by means of a pair of hooked jaws, which fit over the rounded
and notched head of the broach. This will be easily understood by closely
inspecting the ends of the broaches in the front of the machine. This allows
very rapid handling of the broaches, it being unnecessary to drive out keys
as usual. This method of locking has been in successful operation at this
plant for a long time.
Fig. 43-Finishing ends of expanding rings.
FINISHING ENDS OF EXPANDING RINGS
Special attention is called to the method of finishing the ends of expansion
brake rings shown in Fig. 43. The fixture was made by the Lapointe Machine
Tool Co. and is so made that the work is held securely and truly, yet is
easily removed or put in. A pin at the top goes through a reamed hole in
the ring while below two setscrews in posts locate and lock each end of the
ring on either side of the broach, so that they cannot spring away from the

PULL-BROACHING WORK AND PRACTICE 47
cut. The broach is channeled out on top and bottom and these grooves are
run over steel guides set into brackets on the face-plate of the machine.
By this method the broach is guided straight and true as it is drawn through
the work.
FIG. 44-Four splined steel gears.
BROACHING FOUR SPLINE HOLES
The Bullard Machine Tool Co., Bridgeport, Conn., broach four spline
holes in some gears made by them for outside parties. Fig. 44 shows two
of the steel gears, and a gear being broached is shown in Fig. 45. The teeth
Fig. 45-Broaching splines in gears.
of the broach for this particular job are 34 in pitch and o.44 in. in width.
The lands are oo'ſ in wide, with a 5-deg. slope. Back of the land, the
slope is 30 deg. to the channel at the base of the tooth. This channel is
316 in. wide and somewhat flattened on the bottom, having a fillet of 316 in.


48 BROACHES AND BROACHING
radius on each side of the bottom, and so made as to give a 3-deg. undercut
to the tooth. The undercut and smooth fillet give the steel chips a nice Curl.
The outside of the broach is 2.192 in. in diameter at its largest part,
and the broach, 48 in. in length, is made from a bar of 2% in. Steel, cut to
length, centered, and the scale turned off. The piece is then annealed,
after which it is turned and milled to shape, allowing o.o.24 in. for grinding.
After hardening, the broach is straightened on centers to within o.o.o.5 in.
of true and then ground to size.
This job is typical of splining work, whether of four or a dozen splines.
Solid keys or feathers are also cut in the same manner with equal facility.
A DOUBLE-END BROACHING MACHINE
In an article in the American Machinist, Fred. H. Colvin describes a big
double-end broaching machine built and used in the shop of the Winton
Motor Co., Cleveland, Ohio. After experimenting with quick returns for
the screw which pulls the broach, it was decided to build a double-acting
machine so that a constant cutting speed could be maintained and work be
done continuously. This machine is shown in Fig. 46.
After the operator starts a broach through a piece of work at one end, he
goes to the other end of the machine and repeats the operation, there being
ample time to do this during the cut; in this way there is always a broach at
work, even though each end, considered by itself, runs back idle as in the
usual machine. The broaches are held by a simple clamp, made in two parts,
and held in place by a sliding collar.
The principle of the machine is simplicity itself, as a single drawnut is
used, set in the middle of the machine bed between guide brackets, and re-
volved in either direction by means of a worm and worm wheel driven from
a pulley at the side. Two belt speeds are available by using the two-step
cone. By setting and driving the screw in this way, a screw only about the
length needed for a single machine is necessary. Several of these machines
are in use in this shop, and they are built powerful enough for any broaching
job they may have in the manufacturing line.
BROACHING AN INTERNAL CAM
We now come to some of the more specialized forms of broaching and
show a few jobs that will give something of an idea of what can really be
done where the quantity desired will warrant. Fig. 47 shows the broaching
of a gear which has four cam-like surfaces around the central hole. The gear
is steel I}4 in. thick. The cylindrical hole in it is 4% in. in diameter. The
width of the cam surfaces is about 11%. 6 in. by about 1946 in. at the deepest
part. The gear A is mounted on the stub B which is provided with a slot
for the broach. Indexing is taken care of by the index pin Centering a tooth
Space. From six to seven finish-broached gears are produced per hour.
PU-L-BROACHING WORK AND PRACTICE
49
ſºuſųoetu ſuſuotojų puº-eſqnop v−9° *b1，1

So BROACHES AND BROACHING
Fig. 48.-Cutting internal ratchet teeth.

PULL-BROACHING WORK AND PRACTICE 5 I
The cutting of internal ratchet teeth is illustrated in Fig. 48. This is
done on a Lapointe machine and the job consists of cutting 40 ratchet teeth
around the inside of a nickel-steel piece, like the one shown lying in the pan
under the face plate of the machine. The bore of these blanks is 4% in.
The blanks are held three at a time, in a special indexing fixture, and finished
in four draws at the rate of 30 complete ratchets an hour, within a limit of
o.OO2 in.
The blanks to be broached, are held in clamping fixtures, one of which
is shown on the machine and another on the floor. These clamps have an
arm on them carrying a locating pin, which fits notches in the rim of a
plate fastened to the face-plate, as shown. A work bushing serves to locate
the clamp and guide the broach. When one cut has been taken, the broach
is run out and the arm of the clamp is moved around, so that it fits into the
next notch of the index plate, and then another cut is taken, and so on till
completed. Two clamping collars are used, so that one may be loaded while
the machine is broaching a set of blanks. There are I 2 rows of teeth in
the broach, so that it cuts ten teeth at a time, and overlaps one on each side.
The next job shown in Fig. 49 is the squaring of the inside corners of a
chase used on a Hoe press. The chase is set on the adjusting pads A and
B, over the broach guide F and is locked in place by means of the screw D
and small handwheel C which operates a slide with a V-cut in the end where
it contacts with the corner of the chase. As the broach E is drawn through
the corners are machined out sharp and clean and true with the outside
finished edges of the piece.
BROACHING A 22-IN. INTERNAL GEAR
The illustration, Fig. 50, shows an interesting development of broaching
as a manufacturing operation. This is a No. 4 machine, built by the J. N.
Lapointe Co., New London, Conn., the gear being mounted on a large rotating
indexing fixture to which the supporting bracket for the broach is rigidly
connected. This indexing ring has three handles so as to be easily turned,
the indexing teeth being cut on the outside and the locating pin placed directly
above the broach.
This gear, which is a drive for a heavy auto truck, is 22-in. pitch diameter,
3 diametral pitch and about 2% in thick, the material being 45-point carbon
steel with a small proportion of nickel added.
There are two broaches—one for roughing and the other for finishing—
these being made from one solid piece of steel and for working on four teeth
at a time. They can be adjusted with regard to the work by means of a
tapered key on which they slide. The first broach roughs out the gear; then,
without dismounting this, the finishing broach is put into place and completes
the gear. The time for machining is about one-half that of any other method.
The pinion, which is 6 in. in diameter, is shown at the bottom of the gear,
The pull on the broach is given as 60,000 lb.
BROACHES AND BROACHING
Fig. 50,-Broaching a 22-in, internal gear.
-

PULL-BROACHING WORK AND PRACTICE 53
BROACHING SEVERAL PIECES AT ONCE
ſ While a number of those jobs already shown are broached in multiple a
few more special ones are shown here. Fig. 51 is unusual since the pieces
FIG. 51-Broaching three irregular pieces at once.
are irregular in shape and would ordinarily be thought impractical for mul-
tiple work. However, by the arrangement shown, three of these cast-iron
Fig. 52.-Broaching textile machine poppet heads.
pieces are broached at once. The pieces are indicated at A-A-A. They
are cast-iron brackets used in textile machinery. They are made right and


54 BROACHES AND BROACHING
left and have two rectangular holes in them, the larger of which is 1916 by
2% in. Three pieces are broached at a time in the fixture B, which is pro-
vided with the concave lugs C to take the thrust. These pieces were form-
erly filed out, and the time on them was from Io to 20 min. each depending
on the condition of the cored holes. The broach produces about Ioo per
hour. -
Fig. 52 illustrates the broaching out of poppet heads used on textile
machines. They are machined two at a time, two being shown in the
machine and two on the pan, all being indicated by A. The cast-iron
pieces are 3 in. thick and have a slot cut in them 134 in. wide and 2% in.
deep. The pieces to be broached are set on the platform B and the cross-
piece C put in place. The bar D is then screwed down on it by means of
the Small handwheel on screw E. The rate of production on these is about
60 per hour, or one a minute.
THE LARGEST BROACHING MACHINE EVER BUILT (1917)
It is seldom that one can definitely say when a certain machine is the
largest ever made of its kind, but this can be safely said of the broaching
machine shown in Fig. 53. It is shown here because it is not only the largest
machine of its kind ever made, but it is also illustrative of the latest practice
in the use of multiple broaches on a single piece of work. This machine
was made by the J. N. Lapointe Co., New London, Conn. and it weighs
I4,700 lb. and broaches I 2 rectangular grooves at once. These grooves are
% in. wide and 14 in. long. The machine was originally designed for the
use of a large electric company and the work shown being broached is a motor
frame. These frames are 22 in. inside diameter and the holding fixture or
work bushing on the head of the machine, alone weighs 7oo lb. Every part
of the machine is made especially heavy to support the great load. Triple-
operating handles are provided on each side to enable the operator to control
from the most convenient position. A telescoping housing protects the
Screw where it projects at the rear, keeping it safe from injury and also safe-
guarding the workmen. The drawhead nut is made of Lumen bronze, is
3o in. long and is threaded to fit the 5-in. operating screw. The drive is
direct through a silent chain from a 15-hp. motor. The return of the draw-
head is made at the rate of twice the working stroke, 5 min. being the total
time taken to broach the 12 grooves. The outer ends of the cutter bars are
Connected by means of radial springs which draw then to a common Center.
The rear ends of the bars are cut away on the inside so that when the draw-
head is out, ready for the return stroke, the cutters are drawn inward clear of
the work, which can then be easily slipped on or off the work holder on the face-
plate. The machine has a stroke of 6 ft.; is 18 ft. Io94 in. long; 56% in.
wide and 55% in. high, an extra length of 82 in. being required for the stroke
of the broach forward. The screw is 5 in. in diameter with }3 thread to the
inch. The 15-hp. motor runs at 6oor.p.m.
HULL-BROACHING WORK AND PRACTICE
55
-º

56 BROACHES AND BROACHING
A VERY UNUSUAL JOB
The machine and work shown in Figs. 54 and 55 were first shown and
described in the American Machinist of July 9, 1908, yet it is still an example
of unusual work. A Lapointe machine is used. The work itself is a steel
FIG. 54.—An unusual broaching job.
casting having a box-like opening as shown. This is all broached except
the grooves in the center of each side, and it tapers outward J3 in. from each
FIG. 55-The broach used and the work.
corner. The cut must start from the bottom in a shallow recess or chamber,
3 in long. The hole is approximately 8 in square and the cut is 14 in. long.
The broach is in four parts, each sliding on one side of the mandrel, which is


PULL-BROACHING WORK AND PRACTICE 57
tapered to correspond with the hole to be cut, and the four broaches are
pulled together by the rods shown. These rods are arranged so as to allow
the separation necessary as they are pulled up the incline. To put the work
on, the broaches are moved to the extreme outer end of the mandrel, and
project halfway over it. Then the work is slipped on over them. Starting
the machine pulls the broaches up the inclines and starts them to work.
The chips taken out are shown on top of the holder and in the broach. The
amount of stock removed is about 916 in. thick by 8 in. across or around
the corner, and 14 in. long. It is estimated by the builders of the machine
that these broaches require a pull of from 75 to Ioo tons.
EXTERNAL BROACHING
External broaching is continually growing in favor for work of various
kinds which have heretofore been done in other ways. Only a few examples
will be shown to illustrate the main principles involved. Fig. 56 shows a
method of squaring the ends of rods, some of the finished ends being shown
on the rods lying against the machine. The work is done in two operations,
that is with two pulls of the broaches. The arrangement is a jig made in the
form of a box in which slide two broaches with teeth on the inner side to
broach the two opposite faces of the square to be made on the rod. After
the broaches have finished the two opposite faces on the rod, the rod is reset
for the final cut, that is, the dog in which the rod is fastened is indexed 94
turn, bringing the work in position for the second operation to broach the
other two opposite faces on the square.
BROACHING FLATS ON BEARINGS
Another example of external broaching is shown in Fig. 57. These
bearings are broached to fit the fork shown at B, the piece being slipped in as
shown at A. Two pieces F are broached at a time, being set into the holder
C and the broaches D and E drawn through the outer guides, broaching the
flats as indicated.
A job that is commonly milled is shown being broached in Fig. 58.
The piece broached is shown in Fig. 59, the broached surfaces being outlined
in heavy black lines. The accuracy and finish are very close, and from
80 to Ioo pieces are finished per hour, two pieces being broached at one time
by the two external broaches shown. The method of holding is plainly
indicated on the machine.
BROACHING THE OUTSIDE OF A CORE FOR AN AUTOMOBILE-
WHEEL HUB
An interesting job is shown in Fig. 60. This consists in broaching
the outside of a core for an automobile-wheel hub, a blank and a finished
58
BROACHES AND BROACHING
FIG. 56.-Squaring the ends of rods.
FIG, 57,-Broaching flats on bearings.


PULL-BROACHING WORK AND PRACTICE 59
core being shown in Fig. 61. These cores are about 234 in. in diameter and
3 in long. The core is attached to a mandrel and is pulled through a die
broach which makes 36 grooves, 342 in. wide by 364 in deep, at the rate of 45
pieces per hour. This is a record that no milling or hobbing machine could
approach.
Fig. 58.-Broaching a piece that is usually milled.
Two VERTICAL PULL-BROACHING MACHINES
Vertical pull-broaching machines are only built special or are used
for some special job. Under certain conditions they have some advantage
over the horizontal types, though as a rule vertical broaching is push broach-
ing. The vertical machines here shown are the only ones of which we have
any record as being used for pull-broaching work.
2^
Fig. 59–The piece that is broached.
Fig. 62 shows a machine used by the Davis Boring Tool Co., St. Louis,
Mo., to broach out the rectangular tool slots in their boring bars. Another
feature is that diagonal tooth broaches and differential tooth spacing are
used. These broaches will be described in detail in another chapter. The
machine shown is geared 42 to 1 and the travel of the screw is from Io to
48 in per min. on the pull, with an accelerated return. The total possible


6o BROACHES AND BROACHING
screw travel is 38 in. The side bar and uprights are 3% in by 4 ft. and the
screw is 3% in. in diameter. The bars broached on this machine are
of 60-point carbon steel and range in size from 134 to 6% in. in diameter,
some of them weighing in the neighborhood of 3oo lb. The slots for
º V*
FIG. 60-Broaching a core for an automobile hub.
the cutters are first milled in the bars in a Pratt & Whitney double-
spindle automatic spline milling machine. The slots are milled to within
o.ood to o, or in. of finished width and o.o.o.5 to oor in. of the right length.
They are then broached to rectangular form. Owing to the toughness of
Fig. 61.-A broached and a blank core.
the metal the strain is too severe for a single broach to finish at one pass,
so three are used, two for the ends and one for the sides, the ends being
broached first. The first broach is rounded on the end to fit the milled hole
and gradually becomes rectangular in shape so as to square the ends of the
slot. This broach leaves about oor in, on each end for the second broach to


PULL-BROACHING WORK AND PRACTICE 61
cut. The second broach finishes the ends and is a very important tool, as
these ends must be absolutely square with the center line of the bar. The
third broach cuts on the sides only and to within about ooor in. of the
ends.
Fig. 62.-Vertical machine used for heavy rectangular broaching.
-
The machine shown in Fig. 63 is a keyseating machine used in the shops
of International Harvester Co., Milwaukee, Wis., to keyseat small gas-
engine flywheels. The keyways are finished at one pass of the broach.
The flywheels are placed on the top of the table down over the broach which
is then pulled down through the work. The drawscrew runs continuously

62 BROACHES AND BROACHING
and the drawhead is pulled down over it until the drawnut mechanism hits
a bevel stop at the bottom, which opens the split nut in the drawhead, and
allows it to return to the top as it is counterbalanced by weights which act
FIG. 63.-Vertical pull machine for keyseating.
on the two bicycle chains shown. After the drawhead and broach have
returned to the upper position and the work is in place, the operator closes
the split nut and the broach is drawn down again.

PULL-BROACHING WORK AND PRACTICE
63
LUBRICANT USED FOR STEEL WORK
The J. N. Lapointe Co., New London, Conn., recommends the use of
the following mixture, when broaching steel:
Soda ash. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2% lb
Mineral lard oil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 gal
Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 gal
Mix the Soda ash and the oil, with Io gal. of water, and then add the other
40 gal.
TIME REQUIRED TO BROACH VARIOUS KINDS OF WORK
In Fig. 64 is shown a collection of broached samples, which are numbered,
and following is a description of each numbered piece together with the time
required for the work. The illustration is taken from the catalog of the
Lapointe Machine Tool Co., Hudson, Mass., and is representative of the
average shop practice:
No. 1. HEXAGON HOLE WITH ONE ROUND SIDE.-Distance across flats 1% in., length
I}% in., material steel. No. 2 machine. Production 45 pieces per hour.
No. 2. Four SPLINEs.-Hole 1% in. diameter, splines 34 by 946 in., 2% in. long,
material steel. No. 3 machine. Production 20 pieces per hour.
No. 3. SQUARE HOLE.-Distance across flats I in., 1% in, long, material steel. No. 2
machine. Production 4o pieces per hour.
No. 4. Four SPIRAL KEYS.—Diameter of hole I in., keys 93 by }.6 in., 2 in. long, mate-
rial steel. No. 3 machine. Production 15 pieces per hour.
No. 5. CLUTCH USED ON MINING MACHINERY.—Diameter of hole 2% in. Double
depth of slots 3% in., length 2 in., material steel. No. 3 machine. Production
20 pieces per hour.
No. 6. SOLID KEY.-Taken from 194-in. round hole, leaving solid key 3% by % in.,
length 2% in., material steel. No. 3 machine. Production 15 pieces per hour.
No. 7. SIX RADIAL SPLINEs.-Diameter of hole 2% in., splines 5% by 36 in., 2% in.
long, material steel. No. 3 machine. Production 20 pieces per hour.
No. 8. HousING FOR BRONZE BEARINGs.-Openings 4% by 1% in., 2 in. through,
material C. I. No. 3 machine. Production from rough casting 20 pieces per hour.
No. 9. SQUARE HOLE.-Distance across flats 2 in., length 3% in., material steel. No.
3 machine. Production from a drilled hole, 15 pieces per hour.
No. Io. SQUARE HOLE.-Distance across flats 3 in., length 4 in., material steel. No. 4
machine. Production from drilled hole, 15 pieces per hour.
No. II. THREE DOVETAIL SPLINEs.-Diameter of hole 1% in., splines I by 316 in., 2 in.
long, material brass. No. 3 machine. Production 45 pieces per hour.
No. 12. EIGHT DoveTAIL SPLINEs.--Diameter of hole 3% in., splines 34 by }{6 in.,
3 in. long, material steel. No. 4 machine. Production 15 pieces per hour.
No. 13. SQUARE HOLE.-1% in. across flats. 5 in. long, material steel. No. 3 machine.
Production from drilled hole, 15 pieces per hour.
No. 14. UNIVERSAL Joint PART-Hole 2746 in. across flats, 34 in. through, material
C. I. No. 3 machine. Production 3o pieces per hour.
No. 15. BABBITT BEARING-Diameter 2 in., length 2% in. Broached to exact size,
compressed and burnished. No. 3 machine. Production 60 pieces per hour.
No. 16. RounD Hole.—3 in. diameter, 4% in. long, material C. I. No. 3 machine.
Production from cored hole 3o pieces per hour.
64
BROACHES AND BROACHING
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samples of broached work.
ical
—Typ
FIG. 64

PULL-BROACHING WORK AND PRACTICE 65
No. 17. CRUCIFORM USED IN MINING MACHINERY.—Splines 3% by % in., 7 in. long,
material steel. No. 3 machine. Production from 7%-in. round hole, 7 pieces per
hour. -
No. 18. OVAL-shapFD Holes.—1316 by % in., 34 in. through, material steel. No. 2
machine. Production approximately 600 holes per hour.
No. 19. REvolver FRAME.-Size of hole for chamber 14316 by 1% in., 34 in. through,
material steel. No. 2 machine. Production from rough forging 20 pieces per hour.
No. 20. HEXAGON HOLE.-Distance across flats 2% in., 2% in. long, material steel.
No. 3 machine. Production from drilled hole 4o pieces per hour.
No. 21. Two-SPLINE HOLE.-1}{8 by 916 in., 3% in. long, material steel. No. 2
machine. Production from 34-in. drilled hole, Io pieces per hour.
No. 22. HCLE.—% by }{6 in., 33 in. long, material steel. No. 1 machine. Production
from drilled hole 25 pieces per hour.
No. 23. SQUARE HOLE.-3% in. across flats, 2 in. long, material steel. No. 1 machine.
Production from drilled hole 20 pieces per hour.
No. 24. PEAR-SHAPED HOLE.-Diameter of round broach I in., 13% in. long, material
steel. No. 2 machine. Production 20 pieces per hour.
No. 25. INTERNAL GEAR.—Hole 1% in., 1% in. long, 15 teeth, material steel. No. 3
machine. Production from drilled hole 4o pieces per hour.
No. 26. INTERNAL RATCHET 14o TEETH.-Diameter of hole I in., length 13.6 in.,
material steel. No. 2 machine. Production 45 pieces per hour.
No. 27. Six SPLINEs.-Diameter of hole 2% in., splines 34 by }% in., I in. long, material
drop-forged steel. No. 4 machine. Production 35 pieces per hour.
No. 28. BRONZE BUSHING.-Hole 1546 in. in diameter, 1% in. long. No. 3 machine.
Broached to exact size, compressed and burnished. Production from cored hole
Ioo pieces per hour.
No. 29. MAGNETO COUPLING-Hole 134 in. in diameter, 9% in. long, 20 teeth, material
steel. No. 3 machine. Production from drilled hole 90 pieces per hour.
No. 30. Two SPIRAL KEYWAYS.–Diameter of hole 2 in., keyways 34 by }.6 in., 1% in.
long, material steel. No. 3 machine. Production 4o pieces per hour.
No. 31. TEN SPLINEs.-Diameter of hole 134 in., splines 34 by }.6 in., I}4 in. long,
material steel. No. 3 machine. Production 45 pieces per hour.
No. 32. Tool-STEEL DIE FOR PRESSING TIN TOP ON BOTTLEs.-Diameter of hole I }{6
in.., 7.6 in. long, 21 teeth. No. 2 machine. Production from drilled hole 6o pieces
per hour.
No. 33. FOUR SPLINE.-Diameter of hole 1% in., splines 316 by }.6 in., 1}.4 in. long,
material steel. No. 2 machine. Production 45 pieces per hour.
No. 34. TAPER SQUARE HOLE.-Distance across flats, small end, 134 in., large end 19.6
in., 2 in. long, material steel. No. 2 machine. Production I2 pieces per hour.
No. 35. Four SOLID KEYS.–Diameter of hole I}{6 in., keys 346 by }.6 in., 1% in. long,
material steel. No. 3 machine. Production 20 pieces per hour.
No. 36. BUSHING FOR TROLLEY WHEEL-Diameter of hole 3% in., six spiral keyways
% by }{6 in., I}% in. long, material bronze. No. 2 machine. Production Ioo pieces
per hour.
No. 37. Four SPLINES IN TAPER HOLE.-Hole $3 in. in diameter at small end, 5% in. in
diameter at large end, splines 3% by }{6 in., 33 in. long. Splines parallel with taper,
material steel. No. I machine. Production 25 pieces per hour.
No. 38. FOUR SPLINES.–Diameter of hole % in., splines 34 by 34 in., 34 in. long, mate-
rial steel. No. I machine. Production I 5 pieces per hour.
No. 39. SINGLE KEYWAY. —Diameter of hole 34 in., keyway 964 by }{6 in., 36 in. long,
material brass. No. 1 machine. Production approximately 250 pieces per hour.
No. 40. SINGLE KEYWAY. —Diameter of hole 34 in., keyway 316 by %2 in., I in. long,
material steel. No. I machine. Production 160 pieces per hour.
5
CHAPTER IV
EXAMPLES OF PUSH-BROACHING WORK AND PRACTICE
Many manufacturers consider that for certain kinds of work, the push-
broaching method is superior to the pull method. The broaches them-
Selves have to be made shorter and heavier in order to prevent deflection,
and usually a number, sometimes as high as 20 or more, are required to
finish a hole. This is not so remarkable when one stops to consider the
rapidity with which a push broach may be handled. However, a careful
Comparison of the various jobs described will do more to satisfy a man as to
whether this method is adapted to his particular class of work than would
any lengthy argument.
BROACHING UNIVERSAL JOINTS
Some interesting push-broaching work on universal joints is done in the
shop of the Spicer Mfg. Co., Plainfield, N. J., and the following data and
accompanying pictures were obtained there. Two kinds of presses are
used—hydraulic and crank. The latter, however, is used principally for
emergencies. One of the big 20-ton Watson-Stillman presses is shown in
Fig. 65. In using this machine, a set of broaches is laid in order at one side
of the work. The work is put into the holder and then the man at the
back of the machine sets the first broach in place. The press operator pulls
the valve lever and the broach is driven through, dropping down underneath.
The helper inserts the next broach the instant the ram rises, wipes the chips
off the previous one and lays it on the other side of the machine.
In this way, a set is transferred from one side of the machine to the other,
for each complete hole cut. The ram descends at a steady, uniform rate,
but the return is quick, which is one great advantage of this class of machine.
The average time for the descent and return of the ram is from Io to 15
Sec., depending on the size of broach being used.
The method of holding the work and placing the broaches is more clearly
shown in Fig. 66. Boards are provided to lay the broaches on to prevent
injury to the teeth and the marring of the machine. The method of applying
the lubricant in two good-sized streams close to the work is also shown.
BROACHING WITH A CRANK PRESS
A large crank press used for broaching is shown in Fig. 67. This is not
So Satisfactory a method of doing the work as by the use of a hydraulic
66
PUSH-BROACHING WORK AND PRACTICE 67
press, one reason being that the stroke and return of the ram are made at
the same rate. Another reason is that the speed of the stroke varies accord-
ing to the position of the crank, therefore the speed of the press must be set
so that the fastest speed of the ram, at any given point, does not exceed
FIG. 65.-Broaching on a 20-ton Watson-Stillman press.
the safe cutting speed for the broaches used. This makes the output of a
machine of this kind considerably below that of the hydraulic type.
For work of this kind, lard oil, as well as a number of other kinds, has
proved useless, as the metal would tear. After considerable experimenting,
a heavy oil, known as Vacuum Bolt Oil, selling around 5oc, per gal., is being

68 BROACHES AND BROACHING
used with satisfactory results. Apparently the pressure between the tools
and the work precludes the use of any of the lighter-bodied oils.
Fig. 66.-Closer view of broaches and work
BROACHING CONNECTING-ROD ENDS
Several examples of connecting-rod work with pull broaches were shown
in the previous chapter. Here is shown the push-broaching work done on
connecting-rod ends in the Detroit shop of the Continental Motor Co.
Fig. 68 shows the broaching of the small end. The final diameter of the small
end is o.877 in., the last tooth of the broach leaving it o'S76 in., an allow-

PUSH-BROACHING WORK AND PRACTICE 69
ance of a thousandth for final burnishing. These broaches have seven
lands, although the total length is but 9 in. These lands vary by steps of
o-ooos in. This is a hydro-pneumatic press built by the Chambersburg
Engineering Co.
Fig. 67-Broaching on a crank press.
The main air plunger of this press is 13% in in diameter with 80 lb. air
pressure. The intensifier piston is 2916 in, and the main ram of the press is
44 in. in diameter. The intensifier gives a pressure of 2115 lb. per sq. in.
or a total of 15-ton pressure on the ram. For this work, however, the
pressure runs from 5oo to 6oo lb.
-

7o BROACHES AND BROACHING
Fig. 69 shows the broaching of the large ends of the connecting-rods on a
Lucas power press. The finished size is 1.995 in., the last thousandth of an
inch being secured by a burnisher, which follows the broaching. The broach
*////
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FIG. 68.-Broaching small end of connecting rod.
is 13% in long but carries only seven cutting edges, or lands, as can be seen.
Each land removes o.o.o.1 in., and, with the remaining thousandth to be
taken care of by the burnisher, this makes o.o.o.8 in total allowance for
finishing. -

PUSH-BROACHING WORK AND PRACTICE 71
The pressure varies from 2000 to 25oo lb., while the burnishing requires
from 35oo to 4ooo lb. total pressure. These rods can be handled very
rapidly, 1200 being broached in a day.
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FIG. 69.-Broaching the large end of the rod.
Another connecting-rod job is shown in Fig. 7o. This picture was
taken in the shop of the Packard Motor Car Co., Detroit, Mich. The

72 BROACHES AND BROACHING
press used is of the vertical-screw spindle type. No holding jig of any kind
is used, except a cast-iron block with a hole in the center as shown.
Fig. 70.-Connecting-rod work in the Packard factory.
BROACHING PARTS OF LIFTING JACKS
The Joyce-Cridland Co., of Dayton, Ohio, machine a number of the parts
used in their lifting jacks by means of broaching operations performed in
an 80-ton hydraulic press of their own manufacture.

PUSH-BROACHING WORK AND PRACTICE 73
CHARACTER or THE WORK
Some of the jack parts handled in this manner are illustrated in Fig. 71,
which is a group representing several sizes and forms of broaches, a number of
gear wheels for automatic geared-lever jacks; a screw-journal jack frame, and
several parts for jacks of other types.
The hexagonal holes in the gears are broached before the teeth are cut,

74 BROACHES AND BROACHING
as indicated by the engraving, which shows a blank with the hole chucked
through the hub, and a pair of such gears with broached bores, one before
cutting the teeth, the other after. These gears are steel castings and they
are made in various sizes for the different jacks. The ones illustrated are
12 in. in diameter.
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FIG. 72.-Broaching hexagon hole through gear-blank hub.
BROACHING THE HEXAGONAL Hole
The hexagonal hole in the gear hub is 2% in across and the distance
through the hub is 3 in. The work is performed in the hydraulic press shown
in Fig. 72, with the gear blank placed in a fixture, through which the broach
can pass, on its way down through the work.


PUSH-BROACHING WORK AND PRACTICE 75
The operation is completed with one broach, leaving an accurate, Smooth
hole which in the assembling of the jack, receives the six-sided hub of the
pinion that operates the jack bar or ram.
FORMING A SOLID KEY, IN A BROACHED HOLE
In the foreground of Fig. 71 there are a number of bases or frames for
Screw-operated journal jacks, and one of these bases will be noticed to the
right of the group of work and tools in Fig. 72. A cylindrical ram is used
in this jack, the operating screw passing up inside the lower end of the ram,
and the latter having a keyway fitting a solid key in the neck of the base that
prevents the ram from rotating with the motion of the screw. This key is
plainly visible in the cylindrical opening at the top of the jack base in Fig. 71.
It is about 36 in. wide in the size of jack illustrated, and is formed at the
same time as the hole itself is finished. Two broaches are used for this
Operation, both of which are shown at the side of the jack base. The One
at the left, that is, the solid broach, performs the roughing of the bearing,
while the other, which is bored out to receive a guide arbor, is used for
finishing.
ORDER OF OPERATIONS
The broaching is accomplished under the same press. The first, or
roughing broach is pushed through the cored hole, leaving a few thousandths
inch of metal all the way round the hole and key for finishing. The jack
base then goes to the drill press, where a hole is put through the bottom for
the lower end of the jack screw and a concave seat machined for the re-
ception of the lower bearing plate of a roller bearing which takes the load
on the screw.
THE FINISH-BROACHING PROCESS
After the work in the drill press is completed, the jack bases are taken
back to the hydraulic press where, with the second broach, the bearing Surface
for the ram and the controlling key are finished.
In this operation, which is illustrated in Fig. 73, the broach is guided on
a spindle or arbor that passes down through the hole at the bottom of the
jack base and assures the broach taking a true course down through the neck
of the casting, leaving a smooth cylindrical guide for the ram, and a straight,
correctly sized key for the splined guide in the side of the ram.
BROACHING OUT A BEVEL-GEAR HUB
A bevel gear is shown in the background of Fig. 71, with a long broach
in front with which a hexagonal hole is formed in the gear hub. This gear is
used on the hexagonal shank of the elevating screw of the jack. Fig. 74
76 BROACHES AND BROACHING
illustrates the work and broach more clearly and also shows the fixture in
which the gear is held during the operation under the hydraulic press.
The hexagonal hole is 'I in across, and about 1% in deep. The ma-
terial is a tough grade of steel. The gear blank is slipped into the fixture,
and the broach is guided by the bore of the gear and the bushing secured in
the top of the fixture. The cut is divided over 12 cutting edges and one
broach does the work.
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Fig. 73.-Broaching a guide bearing and solid key in jack base for ram.
BROACHING REVOLVER FRAMEs
In the shop of the Iver Johnson's Arms and Cycle Works, Fitchburg,
Mass., the cylinder space in revolver frames is broached out in a vertical
machine, as shown in Fig. 75. The holding fixture is shown detached, and
without a frame in place, in Fig. 76, the method of clamping being clearly
shown. The broach is seen at A, and at B is a gage used to show whether the
frame is being broached out so as to leave enough for finish on the other
parts.


PUSH-BROACHING WORK AND PRACTICE 77
The method of using this gage is to place the frame over the block C,
holding it closely in contact with the fingers, and then push in the sliding
pins D. The pins have shoulders on them and are pushed in against the
frame. If the shoulders are flush with the block, the work is correct, but
if the shoulders go beyond or project from the block the work is incorrect.
WRENCH WORK
The following is an extract from an article by E. A. Suverkrop, which
appeared in the American Machinist, March 27, 1913.
Fig. 74-A sub-press fixture for broaching gears.
The drop-forged wrenches manufactured by the Billings & Spencer Co.,
Hartford, Conn., are so well known that the finished product needs no
introduction. However, the methods used in their making will probably
be of interest.
Apart from the operating screw and the small screw which holds this in
place, the adjustable automobile wrench consists of but two parts. Both
of these are drop forgings. The handle member has nothing of special
interest about it, but the moving jaw is a particularly interesting piece of
work. The rough forging with flash still attached is shown at A, Fig. 77,
and at B is shown the forging after the flash has been removed by trimming
dies. The interesting part of the manufacture begins at this stage.


78 BROACHES AND BROACHING
A hole of the correct size is drilled through the cylindrical part of the
forging B. After this the forging is squeezed in a header and assumes the
shape shown at C. The hole drilled in B is of such size that when headed
FIG. 76.-Fixtures and gage used.
up, the oblong hole will be small enough to clean up when the broaches D,
E, F and G are pushed through it.
These broaches are of the push variety used in a Billings & Spencer broach-
ing press. The upper end of each has a female center and the bottom end a

PUSH-BROACHING WORK AND PRACTICE
79
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BROACHES AND BROACHING
Fig. 78.-Billings & Spencer broaching press.

PUSH-BROACHING WORK AND PRACTICE 8I
male center fitting it. These serve to locate the bottom end of each broach
with relation to the one which has just preceded it. The sides of the upper
ends of the broaches are chamfered off so that they are readily located in the
chamfered female slot in the head of the broaching machine. The broaches
are about 6 in. long and it takes about 34 min. to push the entire set through.
The plain piece H merely acts as a pusher for the final broach.
Fig. 78 shows a Billings & Spencer broaching press pushing a broach A
through one of the jaw forgings B. Fig. 79 shows the broaching of the hole
A for the nut in the Billings & Spencer monkey wrench B. A thin sheet-
Steel inspection gage is shown at C. It is provided with a rectangular pro-
jection D to fit the hole broached by the broaches E and F.
A SUBPRESS FOR MOTOR CAMS
In Fig. 8o is shown a subpress designed to be used for broaching the key-
ways in cams for gasoline motors. The object sought and accomplished
was to cut the keyway in correct relation to the rise of the cam. The base
D is of gray iron, machined on the bottom, top of the two uprights and slotted
for the locating plate B. There are two of these plates, one for the inlet
and one for the exhaust cams, both being located on the bed of the subpress
by Screws and dowels. The plates were made of machine steel, case-hard-
ened, and carefully brought to size. The cross-piece C has a steel plate A
doweled and screwed to it, through which the broach slides, being guided by
two keys which fit keyways milled in the side of the broach, which gives posi-
tive location for the cutters. -
The bodies of the broaches E and F are each 8 in. long, case-hardened,
straightened and ground, the tool-steel cutters being doweled and screwed
into slots in the bodies. The holes in the cams are o.875 in. and the keyway
cut is 9% by }.4 in. The teeth of the broach increase in size by o.o.o.2 in. and
the first one takes out a little over }{6 in., leaving not quite as much more
for the second one. These broaches have been used on over 2000 cams and
are still in good shape.
USING SINGLE-TOOTH BROACHES
A rather unusual way of broaching out square holes in parts for pneu-
matic hammers is shown in Fig. 81. The piece A represents the class of
work broached, and B a finished piece. Seven single-tooth broaches, shown
in order at D, E, F, G, H, I and J, are used. The shanks of the broaches are
splined, so as to fit the holder properly to follow each other in the correct
position. One of the holders is shown in the press, and another near the
broaches, both being lettered C. The work is done in the Cleveland plant
of the Chicago Pneumatic Tool Co., and the press is a Watson-Stillman.
Very fast work is done with these broaches, and the cost of making and up-
keep is very low.
6
82
BROACHES AND BROACHING
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FIG 79.-Broaching a wrench handle.
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FIG. 80.-A sub-press for motor cams.




PUSH-BROACHING WORK AND PRACTICE
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Fig. 81.-Using single-tooth broaches,

84
BROACHES AND BROACHING
FIG, 82.-External broaches for splitting bearings.

PUSH-BROACHING WORK AND PRACTICE 85
EXTERNAL BROACHING WORK
The picture shown in Fig. 82 was obtained by Fred H. Colvin at the Ford
Motor Co., Detroit, in 1913, and represents the practice of splitting bearings
with an external broach. The bearings are first bored, reamed and turned
on the outside. Next a broach with small cutters on opposite sides is forced
through the inside. These cut V-grooves opposite each other through the
bore. Using these grooves to locate the position of the bushing in the punch
press, as shown in the illustration, the outside is cut so that it is an easy
matter to split the halves of the bushings apart by the simple but ingenious
device of inserting a split shell and forcing a taper mandrel through it.
This avoids all injury to the inside bearing surface, as might be the case if
a wedge were forced directly against the inside surface itself.
Some interesting external broaching operations are shown in Figs. 83
and 84. These are done in the shop of Frank Mossberg, Attleboro, Mass.
Fig. 83 illustrates the cutting of the type of rack shown at A, these being a
part of an invisible transom lifter. The job requires three settings in the
broaching fixture, but is easily located so that the racks match up nicely.
As will be seen by a close examination of the broach B, there are I6 broaching
Cutters, to divide the work up, avoid excessive chips and increase the life of
the broach. Each broaching cutter is separate and firmly held between the
spacing blocks shown. In this way any particular cutter can be replaced
in case of accidental damage. -
The broach slides in the opening of the broaching fixture, being well
guided on three sides and providing ample room for the chips between the
different broaching cutters. There remains little to be said in regard
to its operation, the work being satisfactory. -
Fig. 84, shows how the outside of the sliding jaw of a small monkeywrench
is finished. The broach A works through the opening C, the back bearing
against the plate D, which supports it while it is at work. The broach B,
connected to the same holder as the broach A; slides through the opening E
and is duly supported as shown. The work is held in the jaw F, operated
by the crank handle G. The surfaces broached are indicated by the arrows
at H.
THE MANDREL PRESS AS A BROACHING MACHINE
Paul Campbell, writing in the American Machinist, says:
We use a mandrel press to broach keyways in small cast-iron pulleys.
These pulleys have a 362 by 346 in. keyway, I in. in length cut in them with a
broach at a single pass, at the rate of one a minute.
The broach is made of a piece of tool steel I 2 in. long, set into a machine
steel bar 15 in. long and 1316 in. in diameter, which is the size of the pulley
bore. The teeth of the broach are 96 in. pitch and taper from ooo3 to
o.O93 in.
We also cut a 316 by 36 in. keyway in a steel gear with the same-sized
86 BROACHES AND BROACHING
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FIG. 83.-Rack-cutting broach and fixture.
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Fig. 84.-External broaching a wrench part.



PUSH-BROACHING WORK AND PRACTICE 87
hole, using two broaches, and the average time, including handling, is under
2 min. A cast-iron plate, counterbored to fit the pulley hub, is used to rest
the work on, and no clamping is required.
MAKING USE OF A SUBPRESS
E. A. Ermold, in the American Machinist of May 16, 1912, writes:
More than a year ago the hand reamer, as a means of sizing and finishing round
holes, was superseded in our shop by the broach, and since then a considerable
saving has been effected in the cost per hole finished, and in addition the work
produced has been so uniformly accurate that we are now able to manufacture our
product on what is known as the interchangeable plan.
On about 50 per cent. of this class of work an accurate round hole is the starting
point in the cycle of operations. In this connection when speaking of an accurate
hole it is not amiss to state that the average reamed hole is very inaccurate when
Subjected to the critical inspection which our work now undergoes. -
The principle involved in the broaching process is inherently more accurate
for several reasons. In the first place it permits a more accurate method of pre-
senting the work to the tool. To illustrate this, compare the manner of starting
a hand reamer with the method shown in Fig. 85. The fixture shown is a subpress
made very accurately and which, it will be noticed, is not subjected to any great
stresses. The press itself takes the strains and it alone is deflected when under the
cutting strain. The function of the subpress is to guide the broach and hold the
work in alignment with it, the work being located by the previously reamed hole.
The subpress, with its interchanging bushings and adapters, is shown so clearly
in Figs. 85 and 86 that a detailed description of the operation is not necessary.
There are, however, a few details which it might be well to explain.
The subpress was made wide enough between the posts to take our largest
piece of work and high enough to take the tallest piece and by using the Sub-
bases shown at A and B, Fig. 86, shallow pieces could easily be operated on.
The method of guiding the broach and locating the work is shown in detail in
Fig. 87. -
The guiding bushing B is a snug fit in A; C is the broach, the shank of which is
smaller than the body; in practice it must be slipped into the bushing B before the
latter is inserted in A. This procedure prevents injury to the cutting edges by .
being passed through a hard bushing. One end of the locating pin D fits the reamed
hole in the work; the other end is made larger in diameter and fits a supporting
block of hardened steel. The hole being larger than the broach allows it to pass
through without the cutting edges coming into contact with it.
It will be noticed that the broach is not long enough to be forced through the
work at one stroke of the ram; a pin is, therefore, placed on the broach at the second
stroke to accomplish this. It was necessary to make the broaches short on account
of the limits of the press. This is an advantage when making the broaches as they
are easier to make when short.
BROACHING AND REAMING COST COMPARED
The actual labor cost per hole when finished by the broaching method is slightly
less than when hand-reamed, but the greatest saving is in the tool cost. When
88 BROACHES AND BROACHING
reaming the holes we found that we could not ream 25 holes to size with one reamer,
but we have been able to broach 5ooo holes with one 33-in. broach and all the holes
were up to pluggage size. This broach was made for less than $5, which is some-
thing less than the 200 reamers necessary for sooo holes under the conditions
mentioned would cost.
Fig. 85.-Supress in position in the hand press.
Another mandrel-press job is shown in Figs. 88 and 89. The work is
done in the shop of the Dayton Electrical Manufacturing Co., Dayton, Ohio,
and consists of broaching out the brush slots in small generator spiders.
The broach is held by a setscrew in the ram of the press, and is guided by
means of a jig bolted to the press table, as shown in Fig. 88. The work to be

PUSH-BROACHING WORK AND PRACTICE
89
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BROACHES AND BROACHING
FIG. 88—the broaching fixture.
Fig. 89-Work in place for proaching.








PUSH-BROACHING WORK AND PRACTICE 91
broached is placed in the jig as shown in Fig. 89, and the brush slots are
finished at one stroke of the press ram.
A special fixture and broach are shown in Fig. 9o. The brass guide bush-
ing A forms part of a lens-grinding machine. It is about 8 in long and 1%
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Fig. 90-A special broach and work"fixture.
in. in diameter, and is chambered out so that the keyway in it is in two sec-
tions, each 1% in long, 1/4 in wide and 316 in deep. The broach is inter-
esting from the way the cutter is held in place by the two toe pieces. A
spline is cut in the back of the broach bar, to guide it.
1
Fig. 91.-Jig and tools for broaching wrist pin keyway.
BROACHING WRISTPIN KEY WAYS
The hollow-steel wristpins of the pistons used on Fiat motors made in
Poughkeepsie, N. Y., are keyed and pressed into place and secured by a
taper-end setscrew, which in turn is secured by a cotter pin. The keyway cut
in one end of the wristpin hole is broached out in a hand press, using the
broaches and jig shown in Fig. 91.





92 BROACHES AND BROACHING
In using this jig, the piston is slipped into it, till the wristpin hole is ap-
proximately under the bushed hole. The bevel-end pin A is then thrust down
through the bushing into the wristpin hole, lining the two up, so that the
first broach may be easily inserted in the bushing, with its pilot in the wristpin
hole. This broach is then pushed through and is followed by two others,
which cut the keyway to size.
A HAND-BROACHING PRESS
A hand press designed by A. C. Pletz, is shown in Fig. 92. This was not
intended for broaching keyways over 94 in. in size, or 2 in. long. Where a
number of holes the same size are to be keywayed, the broach holder may be
made the same size as the hole, or if desired, an eccentric work bushing may
be used and the broach holder made to slide through it. The broach is
made of rectangular stock and is set into a slot in the holder, as shown. The
capstan wheel is fastened to a threaded sleeve shouldered at H. The screw
C has a keyway cut its entire length, and a key is placed at G to prevent the
Screw and broach from turning when being run down.
While the cut shows the screw cut with a right-hand thread, it would
probably be more convenient for the operator to have it left-hand, as then
the movement would be more natural when forcing through the broach.
Though originally intended only for small work, this form of press can easily
be made for larger work, by varying its proportions.
TURRET BROACH FOR A MANDREL PRESS
Hexagon holes are broached in cylinder caps in a mandrel press, using
the turret broach shown in Fig. 93. The blind holes in the caps are cham-
bered out at the bottom for clearance, and then the turret broaches are
forced in, one at a time. The pin A serves to locate the broaches correctly
and also to lock them in place during the cut. The “teeth” of the broach
increase about o.o.o.2 in. in size.
BROACHING KEYWAYS TO A SHOULDER
The method used to broach out small brass parts to a shoulder is shown
in Fig. 94. The part is slipped down into the holder on the bed of the man-
drel press, the holes in the flanges fitting over pins in the bottoms of the slots
in the sides of the holder collar. A steel collar that fits the turned body of
the casting is then placed over it and locked down by the two thumb-screws
shown in the sides of the holder. The bored hole in the brass Casting is,
of course, chambered out where the two keyways end, so that the broaches
can make a clean cut.
The broaches are double-end cutters set into separate bars in a sort of
turret. There are six double cutters in all, each one being larger than the
PUSH-BROACHING WORK AND PRACTICE 93
preceding one. The bars that hold the cutters fit the bored hole of the cast-
ing and act as pilots for them. The indexing is done with the left hand as the
right operates the lever.
Fig. 93-Turrent broach for a hand press.
CUTTING OIL GROOVES IN EIGHT HOLES AT ONCE
Oil grooves are cut in the push-rod guide holes, in Ford cylinder castings,
by means of small broaches forced through eight at a time, in an ordinary
mandrel press fitted as shown in Fig. 95. The teeth of the broaches are cut
with a slight spiral, so as to give the oil grooves the proper twist.
The cylinder casting is placed upside down on the table of the press,

94 BROACHES AND BROACHING
and the operator places a broach on the inside end of each hole, where it
rests on the teeth which are to do the cutting. Having the eight broaches -
in position, the handle of the press is brought down, and the eight studs in
Fig. 94-Broaching keyways to a shoulder.
the special head B force the broaches through and out of the holes. It will
be noted that these studs are not all the same length, and, therefore, do not
all commence work at once, making it easier to force the broaches through,

PUSH-BROACHING WORK AND PRACTICE 95
though the cuts are not heavy, and the power required is not great in any
CaSe.
-
- - - -
Fig. 95-Cutting oil grooves in tight holes at once.
In the positions in which the broaches are shown at A, they are about
to drop through, to be picked up by the operator and used again. The dis-
tance between the projecting lugs, which form the guides for both the valve

96 BROACHES AND BROACHING
stems and the push rods, gives an idea of the length of the broaches and of
the simplicity of the whole proposition.
- -
FIG. 96.-Horizontal hand broaching machine.
HORIZONTAL HAND-BROACHING MACHINE
While the machine shown in Fig. 96 is not a push-broaching machine,
it belongs among the hand machines and may as well be shown here as
Fig. 97.-The adjustable broach used.
anywhere. In fact with slight modifications, it would make a good hand
press for numerous push-broaching jobs. This machine was made and is
used in the shop of Adolph Muehlmatt, Cincinnati, Ohio. It is used to
broach out the jaw slots in engraver's ball vises. These slots are first milled


PUSH-BROACHING WORK AND PRACTICE 97
to approximate size and then finished by broaching. The device consists
of a base D, a work holder E, a slide F for drawing the broach through the
work, and a long lever G for operating the slide through the medium of a
pawl and ratchet, and a rack and pinion under the slide. The broach used
is shown in Fig. 97, and is of T-section to correspond to the T-slot wanted.
There are two notches in the shank end of the broach which are adapted to
be engaged by pins in the coupling member H. The latter is attached to
the top of the slide F, and its outer end is pivoted to the body so that it may
be swung up to clear the end of the broach or dropped into the horizontal
position represented with its projecting pins engaged with the notches in
the bottom of the broach.
The turntable to be operated on is dropped into a seat in the fixture E,
the broach is slid into the T-slot from the rear, and the coupling member H
is swung down to engage the end of the broach and at the same time align
the work with the slide F. The two setscrews in the fixture E are then
tightened sufficiently to prevent the work from moving, and as these screws
take a bearing against the rounded upper portion of the turntable they hold
it firmly down in its seat. The broach is now pulled through by manipulation
of the long lever. The connection between the lever and pinion stud under
the slide being by pawl and ratchet, the lever is adjustable immediately to
any angle or height best suited to the operator, and can thus be operated
through the arc found most convenient and effective.
The broach itself is so constructed as to admit of a reasonable amount of
adjustment to facilitate holding to standard width. A slot is milled in the
body for over half the length and the broach in two sections is attached to
the metal at each side of the slot by screws passing down from the top. A
wedge of very slight taper is inserted in the slot and gives the necessary
degree of expansion for the broach sections.
BROACHING ON A SHAPER
The cuts, Figs. 98 and 99, illustrate the way the Smith & Mills Co., Cin-
cinnati, Cut keyways in small steel gears. An open box casting A, having a
hole bored in the front wall for the slotted mandrel B, on which the gear E is
placed for keyseating, is bolted to the knee. The cutter blade C, about 4
ft. long, I in. wide, and of the thickness required by the width of the keyway,
is drawn through the gear by the successive strokes of the ram. The teeth
on this broach are so made that each tooth removes about o.o.o.2 in. of metal.
The ram motion is transmitted to the cutter by the notched bar and the
latch H. The notches on the bar are 6 in. apart and the stroke of the ram
is set to a movement slightly more than this, or to 12 in. if the cut is not
very wide or deep. To pull the cutter 4 ft. on the short stroke, which is used
for the larger keyways, requires eight strokes. The thrust of the casting
is taken directly by the column through two screws, one of which is shown
7
98
BROACHES AND BROACHING
FIG. 98-Shaper broaching fixture.
º º ºn
º!
- º - -
--
FIG. Ioo.—Broaching out D-washers.


PUSH-BROACHING WORK AND PRACTICE 99
at D. Guides like G, bolted to the under side of the ram, support the bar
but do not interfere with the regular use of the shaper. The latch H
consists of two pieces of flat steel reduced to half thickness where they over-
lap, and which are pivoted on the screw I, on which they swing freely.
When the ram moves forward, the leaves swing apart and drop into one of
the notches of the bar on the return stroke, the action being the same as
that of a pawl. -
The method used by the Cincinnati Shaper Co. to broach out D-washers
on a shaper is shown in Fig. Ioo. The angle plate used to hold the washers,
which are first drilled out, has a hole through it for the broach and is also
slotted on the face just enough to hold the washer in the proper position.
The broach is held in a sort of split collar in place of the usual clapper box,
being clamped in by means of a setscrew. As a washer is broached it is
pushed back onto the shank of the broach, others being dropped into place
in the slot of the angle plate by hand at each stroke of the ram, till the shank
of the broach is full, when the setscrew is loosened, the broach removed and
the washers dumped into a box. The broach is then replaced and the opera-
tion repeated. -
A SURFACING OPERATION
A pair of broaches laid on parallels and clamped in a shaper vise were
used in one shop to finish off the sliding surfaces of wrench jaws, in the
absence of a suitable miller. The part of the wrench jaw to be finished is
shown at A, Fig. IoI, and the two broaches used at B-B. The piece C was
clamped in the tool post of the shaper to push the jaw over the broaches,
and as the broach teeth were properly proportioned, the job was done at
one stroke of the shaper ram.
A SHAPER TURRET
An interesting operation on a shaper is shown in Fig. IO2. This is done
in the Billings & Spencer shop, Hartford, Conn., and consists in broaching
the hole for the sliding jaw of an adjustable S-wrench. Two parallel holes
are first drilled through the forging and then the bridge between them is
removed by a species of end mill.
The forging then goes to the shaper. The head A carries either two
or three tools B. For this size hole two tools are used; the seat C, it will be
observed, has no tool in it. A trip fastened to the frame of the shaper lifts
the indexing pin on the return stroke of the ram and permits the head to
be rotated to bring the next tool into working position. The work is secured
in a fixture D.
BROACHING ON A PLANER
In a short article, H. B. McDermid says:
In manufacturing one type of Parsons turbines the problem of cutting a large
number of special slots in connection with the blading work was put up to the boss
*
• a vº
• * * *
e
IOO
BROACHES AND BROACHING
4–
FIG. IoI.-A surfacing operation.
FIG. Ioz.-A shaper turret broaching attachment.



PUSH-BROACHING WORK AND PRACTICE IOI
tool maker for Solution. The stock was brass or bronze in the form of disks about
34 in. thick, averaging perhaps 30 in. in diameter. Each disk contained a large
number of slots; and as there were quantities of the disks to be machined, it was
important to devise Some method that would permit rapid production.
Fig. Io94 shows the design of the piece, and an enlarged view of the special
slots to be cut. The disk was mounted on a heavy disk or jig of a diameter enough
Smaller So that the supporting jig or fixture just cleared the bottoms of the slots
of the finished piece.
The whole contrivance was then mounted upon the crossrail of a planer, and a
Spacing device was connected to the regular planer feed system so that with each
Stroke of the planer platen the work was revolved through an angle equal to the
Spacing of the slots and rigidly held in place during the cutting stroke.
The multiple-toothed broach was clamped in place on the planer bed. This
broach was made in sections, the first tooth being the shortest and the line of the
points of the others forming an acute angle with the planer platen, so that each tooth
would remove a chip from the stock and the last one would finish the slot to the
desired depth. The section A of the tool had side points parallel to the planer bed,
for cutting the side notch A in the slot. Its first tooth started the slot, and
its last completed the work to finished size. Thus with every stroke of the planer
a slot was completed to size, the tool withdrawn, the piece revolved by the feed
mechanism through the proper angle, and another cycle of operations started.
The work, being mounted on a tool head, could quickly be adjusted both hori-
Zontally and vertically; and once set at the proper height with its vertical center line
Over the tool, the work could be completed very rapidly, the changing of blanks
necessitating the only pause in the job.
It will be noticed that the small side slot complicated this tool problem some-
what, as for a plain slot several other methods might have been used. In this
instance only one block was machined at a time, but with a more rigid fixture
Several might be machined.
In another short article, Charles H. McCarter says:
The illustration shows a broaching operation on igniter stops for gas engines,
which may be applicable to pieces of a like nature in shops not equipped with a
broaching machine, or where the quantity of work turned out does not warrant the
expense of installing one.
In Fig. Io9 B is shown the drop-forged igniter stop before broaching. It is
first drilled and turned true on the sides preparatory to broaching. The work is
then placed in the fixture shown and located in its proper position by the two
pins. A V-block, set directly in front of the fixture, furnishes the seat for the stop
and also acts as the guide for the broaches.
The first broach is placed in position in the V-block, and the stroke of the planer
is adjusted. Then the planer is started, forcing the broach through the work by
means of a hardened block of tool steel fastened on the front of the head.
Three broaches are used to bring the hole to size. They are made with a pilot
on the end with about o.o.o.2-in. clearance in the work. Each broach is made with
a radius on the edges, the radius getting smaller toward the rear end. The fina
broach is made with a small radius gradually decreasing toward the back until about
I O2 BROACHES AND BROACHING
I in. from the end; the rest of the cutting part of the broach is left with perfectly
sharp edges. The broaches are made slightly taper on the rear end, as the blows
-Tjºs.
..~ ... -- ~~\}\} {j}} "-- ~,
2’ ~~~ ~, -
2 ”
" * - - - - - "
_ _ _ _ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * * * * * * * * * * * * * * * * * * *
1- - - - -
Elevation
ETI Part Plan
FIG. Io 3 A.—Turbine drum and broach.
_l11 =
N Şs
T
J-Chuck
;
FIG. IO4.—Broaching spiral slots in a lathe.
received tend to upset them a little. The speed of the planer is made considerably
slower than usual, in order not to break the tools and to give them time to cut.





PUSH-BROACHING WORK AND PRACTICE IO3
This operation is entirely satisfactory, and the pieces are done at a fair rate
of Speed. After the broaching operation the pieces are put on a square mandrel,
five at a time, and a milling cut is taken at 4, bringing this face correct with relation
to the square hole.
BROACHING SPIRAL SLOTS IN A LATHE
An adaptation of the lathe to broaching a keyway in a bushing is shown,
Fig. IO4. These bushings were required in small quantities and the keyway
had to be an accurate spiral. *
To accomplish this a number of short broaches of slightly increasing
diameter were used, one of which is shown in position; and in these broaches
a spiral slot A was cut.
The work is held in special chuck jaws, as shown, which give clearance
in the back to permit the broaches to go through the work. By throwing
in the back gears with the bolt that connects the gears to the pulley locked
up for direct driving, the spindle of the lathe is locked so that it will not
revolve. Over the tailstock spindle a sleeve B is placed. In the center of
the work to be broached a hole C is drilled, and in this hole is driven a pin D.
For broaching, the shank of the broach is placed in the sleeve B, the teat of
the broach is guided by hand into the hole of the work, while the slot A is
Caused to engage the pin D. Then by turning the handwheel on the end of
the tailstock the broach is forced through the hole in the work and made to
revolve as the spiral groove travels along the pin. Thus the keyway is a
true Spiral, following the groove. Each broach will follow the path of its
predecessor, as the broach teeth are cut with due regard to their relation
with the groove. It is necessary on this work to remove the part from the
chuck after each broach has been passed through, in order to withdraw the
broach.
A TURRET BROACHING MACHINE FOR GUN-RECOIL VALVES
A gun-recoil valve and casing are shown in Fig. Toš. These are used to
take care of the recoil of the guns by means of oil flowing through the ports.
The Special machine used to drill and broach out the ports is shown in Fig.
Ioff. Each valve has 1382 holes, o.140 in. in diameter, drilled through the
wall. Where the rectangular ports are to be broached, the holes are drilled
as close together as possible. The walls are 7.62 in. thick and the valves are
4}{6 in. in diameter. --
The work is mounted on the index centers B, the index flange being
drilled to receive the index pin H. Behind the flange is a worm gear and
worm operated by the handwheel C, when it becomes necessary to shift to
the next row of holes in circular spacing. For longitudinal spacing a pre-
cision screw G, cut by Brown & Sharpe, is used. The carriage C carries
the driller and its motor at the back, while on the front is mounted the
IO4 BROACHES AND BROACHING
turret. Secured in the turret proper are the seven broaching tools D,
which are of the single point, increasing-size variety. The broaching is
done by hand, the handwheel E giving ample power.
This machine is used in the shops of the Detrick & Harvey Machine Co.,
Baltimore, Md., on government work.
--twº
*******************************************************************************º-
FIG. Ios.-Gun recoil valve and casting.
FIG. Io9.—Gun recoil valve drilling and broaching machine.
TURRET MACHINE FOR SMALL SQUARE HOLES
A machine working on the same principle as the one just described, is
shown in Fig. Ioy. It is used for broaching out holes from 34 to 3% in square
and about 2 in. long, in forged steel. These holes are drilled on a slant, so






PUSH-BROACHING WORK AND PRACTICE Ios
that it would be almost impossible to broach them out with a single broach
of the usual type without the breakage being excessive. The holes are
drilled out first with a full-sized drill, and then they are squared out with
five tools held in the turret. The first three tools are octagonal in shape,
each a little larger than the preceding one, and the fourth is square, and
almost full size, while the fifth is full or finishing size. Owing to the tough
FIG. Io?.-Turret machine for small square holes.
ness of the steel used in the forgings, considerable force is required to push
the cutters through, and to do this the turret is fed forward by means of a
gear-operated screw. The pinion on the pulley shaft is made so that it can
be easily slipped out of mesh with the screw gear, enabling the operator to
run the turret back or set it where wanted. The work is held in a sort of
pillow block, set on an angle plate bolted to the end of the machine, and
the whole machine rests on a heavy wooden table.

CHAPTER V
THE DESIGN OF PULL BROACHES
In making any type of broach a number of things must be taken into
Consideration, such as the material to be cut, length of the work, amount of
Stock to be removed and the shape of the work. The last in order to decide
upon the manner of holding and whether special fixtures will be needed.
The length and number of broaches will depend largely on the amount of
metal to be removed, the size of the work and the machine available. Hard
and fast rules are not yet developed for use under all conditions, and many of
the Successful tools have been evolved through a series of painful and costly
experiments. There are a few formulas and general rules that may be used
as a basis, however, for ordinary broach designing, and their use will often
Save considerable worrying on the part of the designer. Warning must be
given here to the sticking to any certain formula in laying out broaches for
different kinds and sizes of work, and the formulas given farther along in
this chapter must be used with considerable horse sense. In a large number
of cases it is far better for a shop to send details of their work to firms making
a Specialty of broach making, and depend upon their judgement and experi-
ence to furnish them with satisfactory tools. There are cases, however,
where circumstances do not make this possible, or preferable to the manage-
ment. For these cases data will be found in this chapter sufficient to enable
the designer or toolmaker not to go at the job blindly. One big thing to
keep in mind, when laying out the tooth pitch or spacing, is that differential
Spacing should be resorted to wherever there is any tendency to chatter,
on the same principle as the differential spacing of reamer teeth, which is
now practically universal. Broadly speaking, the pitch of broach teeth
should increase as the length of the hole increases, in order to provide suffi-
cient chip space. The pitch should, within certain limits, be as coarse as
possible without weakening the broach. At least two teeth should be in
Contact with the work at all times. If the work is too thin for this, some
method must be devised of guiding the broach, or else, as in the case of
washers, a number of pieces are broached at once, the washers being held so
as to represent a practically solid hole. If teeth are too closely spaced,
they may either choke up, or require too much power to pull through the
work, either case resulting in a broken broach.
In calculating the pitch of broach teeth for ordinary work, a fairly good
rule is: The pitch of the teeth equals the square root of the length of the
hole multiplied by the constant o.35. Expressed as a formula, this is:
P = V/L X of 5. For convenience in calculating the pitch, R. C. Haynes
Ioé
THE DESIGN OF PULL BROACHES Io.7
has compiled Table I from this formula, giving the pitch of broach teeth for
holes from 94 to I2 in. in length. The table shows the theoretical length
and the nearest fractional dimension to which it is practical to make the
teeth.
TABLE I.—PITCH OF BROACH TEETH

-—º
Length of hole in Theoretical, Practical, Length of hole in Theoretical, Practical,
work, in. in. in. work, in. in. in.
% O. I 75 %6 4 o. 7oo 1}{6
% O. 2 I4 . %2 4% o. 72I 2%2
}% O. 247 % 4% o. 742 34
% o. 277 %2 4% o. 763 %
34 O. 3O3 %6 5 o.782 2%2
% O. 327 316 5% o.802 1346
I O. 350 1%2 5% o. 82O 1316
1% O. 37 I % 5% o.839 2%2
1% o. 391 | *%2 6 o.857 2%2
I}% O .429 %6 7 o. 926 1946
1% O. 445 M6 7% o.959 8%2
1% o. 463 1%2 8 O. 990 T
1% O. 479 | 1%2 8% I , O2O I}62
2 O. 495 % Q I. O50 I}{6
2% O. 525 1.%2 9% 1.979 1%2
2% O. 553 94.6 TO I. Iof 1%2
2% o. 58o 1962 Io9% ſ I. I.34 1%
3 o. 606 1962 II I. I60 J%2
3% o. 631 % II}% I. I87 I}{6
3% o. 655 2%2 I 2 I . 2 I 2 1%2
3% o. 678 1}{6
CHARTS FOR BROACH DESIGN
The charts herewith were plotted by L. A. Williams to assist in arriving
at quick results when used in connection with the design of broaches.
The chart, Fig. IoS, gives the difference in area between a hexagonal
figure and an inscribed circle, and between a square figure and its inscribed
circle. It also gives the corresponding cubic measurement for any length of
work up to Io in. The method of using the chart is as follows: Starting
at the left-hand side of the line opposite the desired inscribed circle diameter,
follow this line toward the right until it intersects with the curved line
representing either the hexagonal figure or Square, as the case demands.
Then from this point follow the intersecting vertical line to the bottom of the
chart, where the area is given in square inches. To read cubic inches fol-
low the vertical line to where it intersects with the angular line representing
the length of work; then from this point follow the horizontal line to right-
hand side of the chart, where the cubic inches may be read.
Io8 BROACHES AND BROACHING
The chart, Fig. Io9, is intended to give sectional area and cubic inches
of metal removed for multispline holes, such as are used in gearson automobile
transmissions. (The results derived from this chart are not strictly correct,
but the error is negligible.) The procedure in using this chart is similar
to that given for Fig. 108. The lower angular lines represent the total
length of all the splines added together; that is, four splines in a piece 3 in.
in length equal “12 L” on chart.
The third chart, Fig. IIo, deals with the relation between pitch and
number of teeth, length of taper, thickness of chip per tooth and the amount
of taper. This chart was made up primarily to give the thickness of chip
Per tooth, as given by the right-hand group of angular lines, but it will be
5
-D->|Area =
00%25 º
:
00 01 0203 04 O5 06 07 08 09 : 11 12 13 4 15 16 (7 8 19 2
Area in Square Inches
FIG. IoS.-Chart to obtain difference between a hexagon or square and inscribed circle.
evident that this may be used as a starting point if so desired, and the other
required quantities plotted from it.
DEPTH OF CUT PER TOOTH
Obviously, while the foregoing tables and formulas give a good foundation
for calculating the pitch of broach teeth they cannot be followed blindly or
for all metals or conditions without making due allowance. The examples
of actually made broaches and the detailed experience and directions of
practical shop men, which will follow in this chapter, will do much to give
the designer a safe working guide to be used in conjunction with the fore-
going data. The amount of metal that each successive tooth should re-

THE DESIGN OF PULL BROACHES Io9
30
-Z
{6 28
\ (o
3 & 2%
& T ÖV 24
@, § 22
3. !! 20
. tº 12%
§ 1014%|1=%3
^+- M Q
£ 3. fºLº |4 3
#5 |6 - "L |2 O
> ſ 24 201
8 8
6
4.
2
I (T) Lſ) l_ſ) t_ſ TY 0
s & 3 ºs s $g to is 83 & #3
C C C C C C C C C,
Approximate Area in Square Inches of One Spline
FIG. Io9.—Chart to obtain sectional area and cubic inches for spline.
P=Pitch of Teeth T-Thickness of
S|| Alſ .
^
^ T
+ T
Q)
tº #T
*S (94."
# ſº |
º H
T
T
5 0 |5 20 25 30 35 40 45 005 00 05 020 035040
—se —ko robe –K+ urbe ºnko rºls --le-
Length of Taper in Inches Taper(Included) in Inches
FIG. I.10.-Relation of pitch, number of teeth, amount and length of taper and thick-
ness of chip.



I IO BROACHES AND BROACHING
move depends greatly on the hardness or toughness of the metal to be
broached. The size of a hole and its relation to the length also affects
the amount the tooth should cut. Ordinarily, on medium-sized holes in
mild steel, the teeth may increase o.oor, o.o.o.2 or possibly o.o.o.3 in. per tooth.
On heavy pieces of brass or cast iron twice this is often safe. On large
broaches for holes above 2 in. in diameter, where the broach will stand the
pull, as much as o.o.o.5 or o.o.1o in. may be employed. One thing that should
usually be kept in mind in laying out the depth of cut, and that is that if the
cut of a tooth is too small it will have a tendency to drag and dull, thus
increasing the power needed to pull the broach through and also endangering
the finish and size of the hole. The length of a broach also depends greatly
on the toughness of the metal and the nature of the hole. On the possible
safe length of a broach depends the number to be employed to finish a
given hole. On ordinary square holes the cutting capacity of a single
broach is about twice its diameter. That is, if a broach is 1}4 in. Square
it has a capacity to cut 2% in. long. When the work is of greater length,
two or more broaches may be required to complete the operation, thus
necessitating two or three pulls.
This, however, depends on the nature of the metal being broached, also
the amount of radius which can be allowed on the corner of a square broach,
as the more flat or radius the work is allowed on the corner, the easier it
makes it for the broach, permitting same to cut a greater length.
Where a designer is in doubt about a broach being able to finish a hole
at a single pass, it is usually better to make two and then when the finishing
broach gets undersize, it can be ground and used for the first broach, and
another made to finish with at a less cost than would a long new one. This is
common practice where several broaches are employed on a hole, and the
entire set can be kept in good shape by making a new finishing broach
occasionally and eliminating the one that was used for the first cut, the others
being accordingly moved down in the order of their use.
The clearance angle on the top of a tooth is usually around 2 or 3 deg.
or less, some broaches having practically no clearance angle at all. In
many cases the best way to provide clearance on the top of the teeth is
to make a narrow land just back of the cutting edge, and parallel with the
center line. After the broach is hardened and ground, this land is stoned
with an oilstone so as to back it off slightly. Back of this land the clearance
may be several degrees to the real slope of the back of the tooth.
The front faces of the teeth may have as much as 6 or 8 deg. of rake, in
order to properly curl the chip, and the bottom of the tooth space should
have as rounding a fillet as possible in order to strengthen the tooth and
to assist in curling the chip. A curved tooth face is better than a straight
rake, though harder to machine properly. The better results amply repay
this on most work.
THE DESIGN OF PULL BROACHES III
DIFFERENTIAL PITCH
While differential pitch of broach teeth is used considerably, no definite
or uniform rule seems available. Some make a practice of increasing
the normal pitch o.o.o.5 in. for each Space up to five, then dropping back
and starting all over again. For instance: first Space, o.5oo in.; second,
o. 505 in...; third, o.5Io in. ; fourth, o. 515 in.; fifth, o.520 in. ; sixth, o.5oo
in. ; seventh, o. 505 in. and so on. One well-known firm uses the following
spacing: o,595 in.; o.605 in. ; o.61o in. ; o.615 in. ; o.625 in. ; o. 595 in., etc.
Other firms use as high as %4 in. or more increase in groups of three,
still others use o.o.o.2 or o.o.o.3 in. increase in groups of five. As a matter of
fact, the main object is to so differentiate the spacing as to do away with the
teeth following in each others chatter marks, which can be done with almost
any varied spacing within reason, and a few thousandths more or less
is not apt to materially affect the result.
DESIGN OF KEYWAY BROACHES
In opening a series of articles in the American Machinist in April, 1917,
Walter G. Groocock writes:
There are many points in broach design that are debatable, and this is particu-
larly true of keyway broaches. They may be made in three different ways, and
each of these ways has its own advantages and drawbacks. These broaches may
be constructed as a simple series of blades that are drawn through the work, being
held in position relative to the work by means of a locating center; or they may have
similar rectangular blades each Secured in its own stock or carrier; or they may be
made with the cutting portion integral with the stock—that is, solid broaches.
The first kind is shown in Fig. III and is especially suitable for single-keyway
jobs. The second system is much favored by Some tool designers on account of the
supposed cheapness of replacing the blades. The third system is at first sight the
most expensive. This, however, is open to question. But suppose they are more
expensive to make. In those plants where the closest of work is required—more
particularly with regard to double-keyway work—such small added cost is more
than offset by the accuracy of the product from the Solid type of broach.
The one great drawback to the loose-blade broach is the fact that it is impossible
to hold the blades sufficiently solid in their holder to prevent their springing to
either one side or the other. As mentioned before, the type shown in the illustration
is most suitable for single-keyway jobs, because the slight angle that may take
place in pulling it through the work is not readily apparent even when a good
gaging system is in vogue. Moreover, any angle that may exist can be readily
accommodated by the single key and, therefore, is not so detrimental from the
assembling point of view as a similar angle in the case of double-keyway jobs.
With this class of broach, the work is placed on the hardened work adapter A,
which has a rectangular groove B milled through it lengthwise. The broaches
should be a good sliding fit in this groove, but owing to the impossibility of keeping
this fit sufficiently close, any variation in the material being broached or any differ-
II 2 BROACHES AND BROACHING
ence in the sharpness of the corners of the broach teeth has a tendency to force
the broach over to one side of the slot. The result of this crowding over is a more
or less slight lean, or angle, of the finished keyway.
Two or more broaches are required to get a keyway out to the necessary depth;
but when the number of pieces to be done will not warrant a complete set, a make-
t
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shift arrangement, as follows, will answer fairly well: Arrange the broach to take
out half of the keyway at a pass, and for the second pass use a parallel gib key, as
shown at C. Should the depth be such that a third pass is necessary, then a thicker
gib will provide for this if the inclination of the broach teeth is adjusted to suit.
While this method may be used as a makeshift on a common grade of work, it


THE DESIGN OF PULL BROACHES II.3
should be pointed out that the more the broach is raised in the slot the greater will
be the error in the result. Obviously, the less bearing surface the broach has in its
adapter, the greater will be the liability of its leaning over sidewise when at work.
For this reason this system of using gibs should never be adopted when good results
are required.
A good method of pulling broaches of this type is by means of the wedge,
Fig. III. The wedge is serrated on its under side, and the broach blade is
serrated to correspond. The top side of the slot should be made rounded, as
shown. The under side of the slot in the pull adapter should also be rounded. .
The reason for this is as follows: In the tension-type broaching machine with
this class of broach it is impossible to get everything in line, and a certain amount
of float should be allowed. This is usually given in the slot and stem (of the round-
stem type of broach). In the type under discussion, if the key and the bottom of the
tension grip are flat, then when the tension comes on, the whole will be rigid.
Consequently, the broach will be sprung, if any misalignment exists. A further
reason for the rounding is that with some jobs the broach must be taken out, when
run back, to put a fresh piece of work on the work adapter. The straight-type
wedge requires a hammer to release it, whereas the curved wedge is easily released
by raising the end of the broach, as shown. º
OTHER USES FOR SINGLE-BLADE BROACHES
The single-blade broach is often used on double-keyway jobs. Where the
quantity of work to be done is small and accuracy is not of importance, it no doubt
fills a want. But compared with either of the other two systems it is slow. One
method used is as follows: The work is first broached out as if for a single keyway.
It is then slipped on the work adapter, Fig. III, and the operation repeated for
the second keyway. The drawbacks of this method are, first, the work is handled
twice for each broach; second, there is little chance of getting close results, because
to get the work on and off the adapter without losing time the key A must be fairly
free in the keyway already broached. Therefore, this allowance added to the
small allowance in the broach slot has an effect on the accuracy of the finished work.
This means that the assemblers have to ease the side of the keys to get the work
together. Consequently, money saved in the first cost of broaches is spent in
another section of the factory, quite apart from any question of interchangeability.
Another method of doing this class of work with a single broach is to have a
dividing arrangement on the broaching machine whereby the work may be indexed
for the second keyway. The drawbacks of this system are the first cost of the
dividing arrangement, the slowness of the method—for not only must each broach
be pulled through twice, but the work must be secured to the indexing fixture—
and the uncertainty of the result, from reasons already stated. There is also another
source of trouble through this method. Owing to the fact that, no matter how well
a broach may be cutting, a certain amount of burr is thrown up, it is necessary to
have the work adapter, or broach guide, rather slack in the bore of the work or it
cannot be indexed without using considerable force. This means additional error
in the result.
The second type to be discussed comprises broaches with blades inserted in a
solid stock. This construction does not appear to give Satisfaction in Service.
8
II.4. BROACHES AND BROACHING
Two methods that have been used are as follows: The broaches were designed to
have the blade secured by means of screws, and each blade was in two parts, held
by a screw at each end. The blades were let into slots in the stock and butted to
the slot end. Although this set of broaches did much work, they were a constant
Source of trouble.
A METHOD OF HOLDING THE BLADES
The other method, which is illustrated in Fig. III, had some interesting points.
It will be seen that the way in which the blades are held is the one adopted on
reamers. The blades are secured in the center by a pad wedge, bearing on a ridge
formed on the blades. This is not shown. The body for the broach has a groove
cut in the end for the ring A. The two slots for the broach blades are milled from
end to end. The ring A forms a stop for the blades, which are kept tight in position
by the screwed ring B. For large broaches where this design can be applied, it
has distinct advantages over the one already mentioned. From the tool maker’s
point of view, advantage is derived from the fact that the slots for containing the
blades are milled through and can thus be ground true after hardening. This
admits grinding the blades correct to width in their flat state and, incidentally,
spare blades may be kept ready for insertion.
Ground ſoffat) Grindina/7 -
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`--Turners Sizes
FIG. II 2.--Double keyway broach with solid cutters.
Coming now to the Solid type, Fig. II2, I have found that this style of keyway
broach gives the best results because of the various reasons stated and for the
further reason that I have never yet been able to keep the inserted blades tight in
their position. Invariably they work loose and are a constant source of trouble.
On the other hand, the only drawback to the solid broaches is that, because they are
solid, they appear to be costly. -
Experience has, however, demonstrated that, when accurate production is
required, the solid type costs less to install and keep in order than do those with
loose blades. In making the solid-type double-keyway broaches the stock is cen-
tered and turned, the size for the tooth portion being taken at the first and last
tooth and turned parallel. Afterward a taper cut from one to the other completes
the turning. Before the broaches are taken from the lathe, the positions of the
teeth are lightly marked by rings made with a pointed tool. The next operation
is milling away the bulk of the material, leaving 962 in. all round for the final
milling. The teeth are cut in the shaping machine with a form tool made to the
correct shape of the Space. This tool is fed downward at an angle of Io deg.,
thus giving the necessary front rake to the teeth. The operation of shaping the
teeth is a very rapid one, as a boy can do this work on Ioo teeth in 6 hr. After
the key slot is milled in line with one of the rows of teeth, the whole broach is milled
down to o.o.15 to o.o.25 in. over size. It is then ready for carbonizing.

THE DESIGN OF PULL BROACHES II 5
ALLOWABLE LOAD PER TOOTH
The allowable load per tooth of a double-keyway broach can only be—with
Safety—the same as for a six- or eight-spline broach working on the same material.
The figuring up, however, must be done differently. The reason for this is as
follows: In double-keyway broaches with the keys at right angles to each other,
when measurements are taken after the milling is done, the measurements are not
TABLE II.-SUCCESSIVE DIAMETERS IN INCHES FOR SET OF SOLID, DouBLE-
KEY WAY BROACHES
No. of broach
No. of tooth --------- - - - - - - - - - - - - -––
I 2 3 4 5 6
|
I I . 49 I I. 564 I.614 I. 664 I. 490 I. 624
2 I. 494 I. 566 I. 616 I. 666 I. 495 I. 628
3 I . 497 I. 568 I. 618 I. 668 I. 5 I. 632
4 I. 5 I. 54 I. 62 I.67 I. 505 . I636
5 I. 503 I. 572 I. 622 I. 672 I. SI I. 64
6 I. 506 I. 574 I. 624 I. 674 I. SIS I. 644
7 I. 509 I. 576 I. 626 I. 676 I. 52 I. 648
8 I. 5I 2 I. 578 I. 628 I. 678 I. 525 I.652
Q I. SIS I. 58 I.63 I. 68 I. 53 I. 656
IO I. 518 I. 582 I. 632 I. 682 I. 535 I. 66
II I. 52 I I. 584 I. 634 I. 684 I. 54 I. 664
I 2 I. 524 I. 586 I. 636 I. 686 I. 545 I. 668
I3 I. 524 I. 588 I.638 I. 688 I. 55 I. 672
I4. I. 53 I. 59 I 64 I. 69 I. 555 I.676
I5 I. 533 I. 592 I. 642 I. 692 I. 56 I. 68
I6 I. 536 I. 594 I. 644 I. 694 I. 565 I. 684
I7 I. 539 I. 596 I. 646 I. 696 I. 57 I. 688
I8 I. 542 1.598 1.648 I. 698 I. 575 I. 692
IQ 1.545 I. 6oo I. 65 I. 7 I. 58 I. 696
2O I. 548 I. 602 || I.652 I. 702 I. 585 I. 7
2I I. 551 I. 604 || I. 654 I. 704 I. 59 I. 7O4
22 I. 554 I. 606 I. 656 I. 706 I. 595 I. 708
23 I. 557 I. 608 I.658 I. 708 I. 6 I. 7I 2
24 I. 56 I. 61 I. 66 I. 7 I I. 605 I. 7 I4
25 I. 563 I. 612 I.662 I. 7 I 2 I. 61 I. 714
26 I. 563 I. 612 I. 662 I. 7 I4 I. 615 I. 7I4
27 I. 563 I. 612 1.662 I. 714 1.62 | 1.714
28 I. 563 I. 612 I. 662 I. 7 I4 I. 62 I. 7I4
T. S. | |
Ist tooth 1.52 1.675 1.745 1.865 I. 52 I. 75
26 Tooth I. 675 1.745 1.865 I. 965 I. 75 I. 96
B I. 488 I. 55 I. 59 I. 64 1.7% I. 59
C O o. 404 o. 403 O. 4O2 O. 4. o. 439
R 1% in. 1%2 in. 1946 in. 1916 in. 1%6 in. 1% in.
W o. 406 o. 405 O. 4O4. O. 4O3 O. 439 O. 439
F | . . . . . . . . . . . | . . . . . I. 693 . . . . . I. 693
*Turn I. 93 |
i |
II 6 BROACHES AND BROACHING
made the full diameter, but only across the body and one tooth. This, of course,
applies also to spline broaches with an odd number of splines. Therefore, the rise
per tooth to be allowed on the table showing sizes for a six-spline broach would be
double the rise per tooth given on the table for a double-keyway broach having the
same load per tooth. -
A standard sheet for this type of broach is shown in the table, made for broaches
with 28 as the maximum number of teeth. This covers the range of length that
can be made on an ordinary-size miller. Two points in Fig. II 2 need special
mention. Keyways, when finished, have square bottoms, while the dimension D is
finished as a radius. This means that the last few teeth have to be ground flat on
the surface grinder. The dimension F covers this point and represents the size of
the hole plus the depth of the keyway in the work. Another point is the dimension
G. This may be expressed either as shown or as the depth of the chip space. As
shown, the chip space would vary in depth. When the spaces are shaped in with a
form tool, R is best expressed as the depth to be cut. To avoid repetition, the load
per tooth and the method of applying the load for keyway broaches will be discussed
under spline broaches, from which they do not differ in any essential detail.
The sizes that were used for a very successful set of broaches are given in
Table II. These broaches have done good work on deep keyways in gears made
from tough steels used in the automobile trade. The lengths of the holes varied
from 3 to 4 in.
DESIGN OF ROUND BROACHES
For years reamers have been used to size holes—say in the drilling
machine—and those who have had most experience with reamers must
know what an uncertain tool a reamer is, yet the round broach for sizing
work is comparatively neglected. While the broach will never entirely
displace the reamer, there are in every plant innumerable pieces of work that
are particularly suitable for broaching purposes, such as levers, single-hole
brackets and the like. Take, for instance, levers; these can be rough-drilled
%2 in. undersize and then broached to size, thus giving a cheaper and better
job.
Broaching is cheap, because a round broach costs little more to make than
a solid reamer of high-speed steel; and yet the broach will produce more
holes within predetermined limits than will a solid reamer. This means
that the tool cost per piece is relatively low and much in favor of the broach;
and while the actual time of sizing the hole does not differ much for Small
holes, for holes over I in. in diameter the broach has a decided advantage.
A type of standard drawing for making round broaches is shown in Fig.
113. The table gives dimension details of a few standard sizes the pro-
portions of which have given satisfaction. It is best to leave the table blank
on the tracing of the broaches, filling the sizes in on a blue-print as different
sizes are put in hand. By so doing any change that experience Suggests as
desirable may be embodied in future broaches without erasures on the
tracing.
THE DESIGN OF PULL BROACHES II 7
TABLE III.-DETAILS OF STANDARD SIZES OF ROUND BROACHES, IN INCHES

Nomi- -
nal A B C D E IV G | J L P | N R r ..&emarks
S126
34 || 0.75 I | O. 735 | . . . . . 1.%2| 134 742 || 4 || 342 25 || 36 || 8 |% |%2 Five notches
% O. 876 O. 86 | . . . . . 94 6 I}.4 %2 4 || 36 || 25 || 36 || 8 |}3 |}{6|Six notches
I I . OO I O. 984 |. . . . . % I}4 % 4 | }.6 25 || 36 || 8 |}6 |}{6 || Six notches
I}% I . I 26 I . I I 34 I}4 34 4 || 36 || 25 || 36 || 8 |% |}{6 Six notches
I}4 I . 25 I I. 2 I5 I}; % I}4 1}42 || 4 || 36 || 25 | 3% | 8 |% |}{6 | Six notches
I93 I. 376 I. 34 I}4 I 1546 || 332 || 4 || 94 || 25 || 36 || 8 |% |}{6 Six notches
I}} | I. 50 I I.47 I36 | I }; 1546 1362 || 4 || 34 || 25 || 36 || 8 |% |}| 6 | Eight notches
I 36 I. 6265 I. 59 || 133 I}4 1546 || 1342 || 4 | }.6 || 25 | }} | 6 |}{6}{6} Eight notches
I34 I. 7515 I. 72 I5% I5'ſ 6 || 13% % 6 || 4 | }.6 || 25 | }% | 6 |}{6%2| Eight notches
1% I. 8765 | 1.84 15% 1746 | 15% 34 6 || 4 | }.6 25 | }.3 || 6 |%i 61%. 2 Ten notches
2 2. OO I5 I 96 I9% | I 91 6 I}3 |. . . . . . 4 | }.6 || 25 | }% | 6 |}{6%2 | Ten notches
Changes that may be found advisable are pitch of teeth, spacing of
notches, or total load. For instance, it will be obvious that the pitch of the
broach teeth must be less than the width of the work, or the work will drop
into the teeth. Consequently, for a thin job like a washer the pitch may
have to be finer, failing some special means of holding the work. On the
other hand, for a very long hole the pitch may have to be coarser, to lessen
the total load on the broach or to provide more chip space. The notching
may have to vary to suit a given material. Usually, however, for sizing
holes up to 1% in. in diameter 3% pitch is satisfactory, and 3.3-in. pitch
gives good results up to 1% diameter. For broaches larger than this the
pitch should be wider; and the depth of the spaces may be materially in-
creased, thus lightening the broach, which makes for easier handling.
While there is no limit to the size of round broach that may be used—
except the power of the machine to pull it—it should be stated here that all
round broaches have a tendency to work downward, owing to their un-
supported weight. Naturally, the effect of this would be greater with the
heavier broaches.
For this reason—among others—it is desirable that broaching machines
should be built with an outboard support, or extension, which should be
integral with the main casting of the machine. A sliding block on this
extension could then be used to keep the broaches in line. Where there is
no support for the broach other than the pull adapter, the work adapter
must be renewed frequently so that the broach cannot sag too far out of
line. These adapter bushings may be bored out to the next larger size and
Consequently may be used again.
Apart from ordinary standard broaches there are many cases where
Special round broaches are of advantage. Malleable-iron castings may be
broached direct from a cored hole when the location of the hole is not im-
portant. For this work, round broaches that have lost their size may be
ground to take out the necessary amount of material. Such a broach would
of course be followed by a standard broach to size the hole. When, the
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II.8 BROACHES AND BROACHING
cored hole is not more than }{6 in. below the required size, a reground
broach may be used without rehardening, but generally, owing to irregular-
ities in the cored hole, the reduction of the broach will necessitate rehardening.
Large round broaches made from case-hardened steel, which have lost
their size, may be brought back to standard by rolling up the last few of the
glūlſº |E|
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L.F.ſ.
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FIG. II.3.−Standard drawing for round broaches.
teeth, say six, and then regrinding these to do the sizing. To do this a
small rollis mounted on the end of a pin I in. square. This holder is mounted
on the lathe rest at an angle, the roll is applied to the front of the desired
teeth, and pressure is applied while the broach is slowly revolving in the
>H3+/67hreads
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FIG. I. I.4.—Broach with detachable end.
lathe. If the tooth faces have been frequently reground to sharpen them,
it is a simple matter to increase the diameter of a tooth to the extent of
o.Or in. If, however, the case at this point is still deep, it takes considerably
more effort to get an increase of, say, o.o.o 5 in. in diameter.
FIG. II 5.-Broach for removing burrs from splined holes.
Very large round broaches may be made with a detachable end, like the
one shown in Fig. 114, the detachable portion being secured in position by a
nut. In this type of broach it is advisable, to get the best results, to work
along the following lines: When the broach is first made, only about two
of the teeth on the auxiliary broach do any work, the remainder being idle
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THE DESIGN OF PULL BROACHES II9
teeth. When the broach has lost its size, beyond the rolling-up stage, the
detachable portion is taken off and a new one taken from stock and secured
in position. The detachable ends should be kept in stock, hardened, ground
in the hole and on the end, but not on the teeth. After the broach is again
built up, the new portion should be ground to size and the remainder of the
broach reground. To do this the taper, or slope, of the broach is slightly
changed, which allows all the teeth to be resharpened on their diameter,
the replaced end having fewer idle teeth than the original end, according
to the condition of the broach teeth that have not been changed. This
design of detachable ends is only applicable to the larger type of round
broach.
Another type of round broach that has been found useful for taking off
burrs from splined holes is shown in Fig. II.5. This needs little description.
Only a few teeth are cut about the center of the broach, the front part of
which is grooved to clear the burrs. The plain back portion acts simply as
a guide to keep the work in alignment. -
Owing to the fact that there is little work for such broaches to do—
that is, they only have to remove burrs—they retain their size for quite long
periods. -
DESIGN OF SQUARE BROACHES
As with other types of broaches, when designing square broaches one is
Confronted with several different methods of arranging them. In the long
broaches it is customary to have the width of the flats practically the finished
size from end to end. There is, however, one very good reason why this
System is not particularly sound practice; and that is, when the broach
loses its size, and it must do so sooner or later, then one has either to put
in another short broach just to size the hole or make a complete long one
and Scrap the one that is under size. Further, if the broaches are designed
to pull out the hole to its finished size across the flats from the start, it will
be found invariably that there are several nasty scores or marks in each
hole. While these drags may not be sufficiently bad to scrap the work,
they certainly do not add to its appearance or utility.
Obviously, the best holes, from a wearing point of view, are those that
have the Smoothest surfaces. This being so, then the endeavor must be
to secure this desirable feature. The cleanest holes that can be produced
by broaching are obtained by making the set of broaches in two parts, one
part of the set pulling the holes out—for square holes—to within, say,
o.oos in. of size across flats for small squares and within o.o.1 in. for large
squares; the final broach in this system then just takes a scrape all over the
hole and leaves it in good condition. Aside from excellent finish by this
method of arranging the broaches the useful life of the set is very much pro-
longed because the finishing broach, having so little to do, will produce many
I 2 O BROACHES AND BROACHING
more holes within predetermined limits than it would if it had part of the
roughing out to do.
There are other good reasons why the finishing of the hole should be
done by the last broach in the set. The time will come when the hole pro-
duced will not be to gage. Although a good sharpening across the face of
the teeth and a second pull through of the finisher will temporarily over-
Come this difficulty, another broach must be used to finish with; and it must
of necessity take a shave around the flats. Aside from the possibility of
replacement by using the last broach to size the flats, one can considerably
lessen the cost of a set of square broaches.
Each roughing broach may be made to just clear the hole left by the
previous broach, and in a general way they may vary, say, o.o.o.2 in. across
the flats below the size that it is intended to make them. This means, of
Course, that the finish grinding of the flats can be considerably hastened,
because less care will be required with such a limit. Consequently, by
adopting this system only one broach in the set needs particular care in
finishing. Those who know the difference between attempting to work to
size and working to a limit of o.o.o.2 in. will appreciate the importance of this
point. The set of broaches should be so designed that the finisher has
nothing, or at most only a few thousandths of an inch, to take out of the
Corners, and this work should be spread over the first few teeth, say o.o.o.1
in. per tooth, thus insuring clean finish to the corners.
By giving the finishing broach very little to do on its corners when new,
one is enabled to regrind the roughers when required; and whatever reduction
takes place on their corners owing to grinding, it can be met by reducing
the first few teeth corners of the final broach. Thus, it is assured maximum
life, while at the same time the broaches are kept in such condition that
they will give good clean results on the very toughest material. To do
this they must be kept sharp.
Besides just touching the corners of the hole the last broach of the set
must take a slight scraping cut along the whole of the flats of the square hole;
and to do this, every tooth must be carefully backed off to a cutting edge.
The roughing broaches should not be relieved on the flats, but should have
a ground land, approximately as shown at A, Fig. 116. The curved front
is due to the undercutting of the face of the teeth, and it will be referred to
again.
In designing Square broaches there is no infallible rule by which success
may be achieved, except the rule that is common to all design—that is, to
base the proportions on the proportions of some successful set, embodying
any new data that experience points to as being either necessary or desirable.
The best way undoubtedly is to draw two teeth of each broach very care-
fully as to size, after one has figured out roughly the load per tooth and the
number of broaches to a set. Two longitudinal views should be drawn,
one taken across the flats and one across the corners. In this way one is
THE DESIGN OF PULL BROACHES
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I 2.2 BROACHES AND BROACHING
enabled to see clearly whether there is enough chip room and whether the
tooth looks strong enough in the corner view. The root diameter should be
checked to see that it is a stronger section than one taken across the pulling
slot of the broach. The difference between a corner view and a view of the
flats is clearly shown in the illustration.
These broaches were for use on steel forgings of from 3 to 4 in. through
the hole. The data for the full square are given at the bottom of the data
sheet, and it will be seen that the set consists of six broaches. The first
and Second broaches appear to have an abnormal load, but in reality their
load is Small. The articles to be broached, one of which is shown in Fig. 117,
are Stamped with a square hole; and naturally the forged hole has consid-
erable draft. After it is bored to 3 in. in diameter, the hole looks as it
appears at A, the line B representing the square.hole on the edge of the forg-
ing and the line C being the center of the piece. The portion shown hatched
at D is the material to be broached out at the corners. It will be seen that
the first and second broach—the first in particular—act on only a short
portion of the hole, hence the apparently heavy load.
This set of broaches proved particularly clean in their cutting, and from
the easy way in which they did their work it is evident that they might have
been loaded still more. But to have put sufficient work on the leading
broaches to enable the cutting out of the fifth broach would, without a
doubt, have considerably shortened the life of the set. It is a great tempta-
tion to the designer, when a set of broaches have been very successful, to in-
Crease the load per tooth on the next similar set that he may design; but it
is always well to remember that every year the material that we have to
broach is getting more and more difficult to deal with. Consequently, the
proposition to be considered is not so much “how many pieces per hour”
as it is “the cost per piece to be broached.”
A set of four broaches may be designed to do a job and work satisfactorily
until they have done, say, Iooo pieces. Then they may fall down badly and
have to be replaced. Suppose the cost of such a set of broaches is $1oo.
The introduction of another broach into this set would increase the cost of
the set by 25 per cent., but it would probably mean that such a set would be
in good order after doing 5ooo holes. If, now, the labor cost for broaching be
considered, in the case of the four-broach set it would be only 20 per cent.
less than that for the five-broach set. One can see at once that the small
saving in labor cost is very much overbalanced by lower broach cost per piece
of the five-broach set. In this, then, as in all good shop practice, the unit
cost of production must be considered and not the labor charge alone.
PROPER LENGTH OF CUTTING EDGE
There is one point in connection with the design of large square broaches
that should be mentioned; that is, the length of cutting edge in the first two
THE DESIGN OF PULL BROACHES I 23
broaches is such that it is preferable to notch the cutting edges, so as to break
up the chips. This notching should be carried out all along the first broach
and part of the way along the second. The notching should of course be
^T.A
D-?
B->ESS » SNSSN
FIG. II 7.—Article to be broached.
FIG. II 8.—Grinding broach with edge of wheel.
staggered, so that, as in milling, one tooth takes out what the previous tooth
leaves.
An interesting Contrast to the large set of square broaches just discussed
is provided by considering the second set of data given in the accompanying
table. This set of four broaches had to pull out a 34-in. square hole up to 3




I 24 BROACHES AND BROACHING
in. long and almost to a sharp corner. The material was a high-grade alloy
Steel used on automobile gears, and on this material the broaches worked well.
This set gave excellent results, and they undoubtedly have sufficient chip
room to work in holes up to 4 in. long. They were designed to work from
a 34-in. rough bored hole.
GRINDING THE FLATS ON A BROACH
The grinding of the flats of square broaches may be accomplished in a
variety of ways; but if a Bath spline grinder is available, then with a cup
wheel Square broaches are a simple proposition. The roughing broaches
should be ground parallel the whole length, and afterward the table should
be tilted so as to taper the guide portion slightly. When grinding the finish-
ing broach, the finishing end—about six teeth—should be ground parallel
and about o.oO1 in. over the size of the hole required. Afterward the guide
and the remainder of the teeth should be ground taper, the guide being of
such size as freely to enter the hole made by the roughing broaches. After
this all the teeth along the taper portion of the finisher must be relieved to a
Cutting edge.
The method adopted to relieve these teeth will of course depend on what
machine is available; but as most tool-rooms now have a small surface grinder,
I will assume that small Brown & Sharpe machines can be used and will
discuss two ways of relieving the teeth, which have been found to give good
results in minimum time. These two methods are outlined in Figs. I 18
and II9.
In the first case the wheel is trued up to a bevel of 3 deg. The work is
laid across the table of the surface grinder and is held at right angles to the
wheel—that is, parallel to the wheel axis—by means of two parallels clamped
to the machine table. The wheel is brought down on each tooth in turn, and
the grinder table is moved by the handwheel, thus traversing the broach under
the wheel. By this means each tooth is in turn brought up to a cutting
edge. When working this way the broach passes through the standards of
the machine and also between the belt. With large-sized broaches there is
likely to be interference by the belt. To protect it from accidentally catch-
ing on the corners of the broach teeth and thus getting cut, it is advisable
to bend a U-shaped piece of sheet steel and lay it across the broach where the
belt may foul.
METHOD TO BE USED FOR LONG BROACHES
For square broaches over 2 in. this method cannot be used, because the
belt rubs badly before the wheel is across the tooth; that is, the travel by this
method—on a small Brown & Sharpe—is limited. In such cases we may fall
back on the method outlined in Fig. I 19. More skill is required in the opera-
THE DESIGN OF PULL BROACHES - I 25
tor, but the process is perfectly safe for any tool maker who has acquired
the “feel” of the machine. The broach to be relieved is laid longitudinally
on the table, being held at right angles to the wheel axis by parallels clamped
to the table. The wheel is brought down between two teeth to a predeter-
mined depth, which need not be varied, and the table is moved longitudinally
So that the wheel just touches the tooth to be relieved. The broach is then
traversed by hand underneath
the wheel by means of the cross-
traverse handwheel; and the
platen of the machine, carrying
the broach, is moved just far
enough to allow the grinding
wheel to relieve the tooth to a
Cutting edge.
This operation, which takes :::::::::
Only a fraction of the time re- *:::::::::
quired to describe it, is then re- \ ^ C º º
peated on all the teeth. The (º
teeth left parallel at the end of º
the broach should not be *-62
brought up to a cutting edge, FIG. I.I.9.–Grinding large sizes of broaches.
but should have about 9%.2-in.
land. The only drawback to this method is, of course, the fact that a curved
relief is obtained, which is greater at the cutting edge than it need be.
However, by using a 7-in. diameter wheel the hollowness of the relief is not
very pronounced.
There is another point about the grinding of the finishing broach that
must be mentioned here, because it materially affects
the design. To get good clean cutting at the corners
of square broaches it is advisable to undercut the face
of the teeth to the extent of about Io deg. If this is
carried all the way along the finishing broach, one will
have difficulty in getting a square hole with perfectly
flat sides, because as mentioned before, the under-
cutting of the teeth gives a curved outline to the
FIG. I.20.-Diagram cutting edge. Consequently, the cutting edge is re-
#: * * lieved by moving a grinding wheel across it in a straight
line. It will be found that the center of the flat comes
to a cutting edge before the outside. This means that if the whole of the flat
be relieved, the broach will be lower in the middle than on the outside of the
flats, and naturally the hole produced will be larger measured at the sides
than it would if measured in the center. This result is shown exaggerated, in
Fig. 120, by the curved lines. The following method gets over this difficulty.
As the finishing broach will never be called upon to cut on the corners,



I 26 BROACHES AND BROACHING
except the first few teeth, the broach need not be undercut the whole of its
length. Differential undercutting may be used, as follows: First four
teeth, Io deg.; next four teeth, 7 deg.; and four following teeth, 5 deg. under-
Cut. All the remaining teeth should have flat faces. The result of this is
that, when all these teeth are relieved to a cutting edge by a straight-line
relief, those that are undercut will cut on the flats near the corners first,
while those with less undercut will take more from the center. The teeth
with flat faces will take a scrape right across and leave a square hole with a
flat side.
The standard drawing recommended for square broaches is given in Fig.
I 21. Blank dimension sheets should be prepared, which may easily be filled
out with the dimensions necessary for any set of broaches. The drawing
can also be used for hexagonal broaches by changing the end view. This
may be done in the way suggested for spline broaches—by means of an aux-
iliary print showing the end views of the various shapes.
All that was said with reference to the data sheet shown in a previous
article applies with equal force to the data for square broaches, in Table
FIG. I2 I.—Standard drawing for square broaches.
IV. This sheet gives the essential particulars of a few successful sets of
Square broaches and needs no further comment.
>k :k :k :}; >}: >}: sk >k >k ::
In estimating the power required to pull a broach through a cored hole,
4% in. Square, and 4 in. long, in a steel casting, in which the cored hole was
broached to a 4%-in. round-cornered hole, J. N. Lapointe estimated the power
needed to be about 16,000 or 17,000 lb.
BROWN & SHARPE BROACHING PRACTICE
Besides doing broaching on various parts for machines built by them, the
Brown & Sharpe Mfg. Co., Providence, R. I., does considerable work of this
kind for automobile or other concerns. A few examples of work done in its
Shops are shown in Fig. I22 and include spur and bevel gears, and cranks
and Collars in which keyways or square and hexagon holes are broached.
Some of the gears in which round-cornered, square holes are broached,
are for automobile transmissions, and Consequently, are of particularly
tough steel, so that for the 1% size, seven broaches are necessary to produce
accurate results without tearing the metal or overtaxing the broaches. The
Set of broaches used for this size of hole is shown in Fig. 123. From this it

Fig. 123.-Set of broaches for round-cornered square holes.
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8& I


THE DESIGN OF PULL BROACHES I 29
will be seen that none is of the excessively long type often seen, but now less
used than formerly. The semicircular recesses in the shanks, in which the
eccentric clamp of the holder fits, are also plainly shown. Details of the
various dimensions and tooth sizes of the I}4-in. Set of broaches are given
in Fig. I24.
TO SAVE TIME IN BROACHING OUT SQUARE HOLES
The fit of gears on a square shaft depends almost entirely on the flat
surfaces at or near the corners, and very little on the center portion of the
flat surface. With this in mind, drill the round hole in the gear slightly larger
than the diameter across the flats of the squared shaft, as shown in Fig. I 25.
Taking a 1%-in. Square shaft and boring the hole 346 in. larger or 1%. 6
in. in diameter, we see in the illustration exactly what this means. The
amount of metal to be cut out is materially reduced, the portion A to B
not being touched by the broach in any way. Yet the remaining surface in
| |
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FIG. I.25.-Broaching saved by boring hole larger.
the corners is ample to carry all the load of the gears at work, and the clear-
ance A to B allows the best of lubrication for the gear and shaft.
There is also another point. The center relief as shown, gives consider-
able added chip space as well as reduces the amount of chip, thus allowing a
heavier chip per tooth. This reduces the length of the broach or allows a
longer hole (such as two gears at once) to be broached with the same length
of broach.
DIMENSIONS FOR HEXAGON, SIX-SPLINE AND BUTTON BROACHES
The fact that in order to stand the terrific strain, gears used in modern
automobiles must be made of the toughest steel that it is possible to use,
renders the machining processes interesting from a number of viewpoints.
Especially is this true of the broaching proposition.
The transmission gears used in the automobiles made by one of the big
companies, are made from chrome-nickel steel, and the broaches used
for working out hexagon and six-spline holes in these gears will be described
in detail.



9
13o BROACHES AND BROACHING
Fig. 126.-Steps in the broaching of a hexagon hole.

THE DESIGN OF PULL BROACHES 131
Three broaches are used to broach out the hexagon holes in the bevel
gears shown in Fig. 126. The separate operations are represented in order
-ººººººººº.
- |.
- - - - - *** * -
Eº
- ºf ººººººººº-ºº: º
- - wº- º - |
E. Hººpºº. --
Fig. 128-First and last steps in broaching a six-spline hole.
by the gears A, B, C and D, two gears being shown for each operation, in
order to show both ends of the hub.







©
ſ
|| || || |
o KM->..N
--> --8 | : K-o-'k Pº
HO L- ) “YS || UD
- d y ^ D–S.
| | STYLE | |
R--------------------------- H-Cuf Teefh fu// Length ---------------------------->|<------ J.------->|<------ K------>
Broac/?
Broach 1.4
1.54
STYLE NO. 1
BROACH D
6-Teefh egva/ly spaced
STYLE NO. 2
FIG. I.30.-Dimensions of six-spline broaches.
3.




THE DESIGN OF PULL BROACHES I33
The proportions of the broaches used are given in Fig. 129, and it will
be observed from this that the first tooth of the first-broach is the same size
as the shank, but that several thousandths are allowed for the entering
teeth of the following broaches. This is done to allow for the wearing or
grinding down of the final teeth of the preceding broach. The last four
teeth of the finishing broach are left the same size to prolong the life of its
accuracy. The length of these hubs varies from 134 to 3 in. and the time
for each broach is I min. 20 sec. and 25 sec. return stroke.
On the gear blanks shown in Fig. 128, five broaches are used. The
first operation is illustrated at A. The fifth operation is shown just
below, and by carefully examining the splines, it will be noted that
Small grooves are cut in the corners, obviating the necessity of cutting to a
sharp corner in order to make the gear slide well on the feathered shaft,
and incidentally greatly prolonging the life and usefulness of the finishing
broach, as it is difficult to keep sharp corners on the teeth of a broach of this
type in such tough metal. The length of these hubs varies from 134 to
3 in. and the time for each broach is 32 sec. with 18 Sec. return, or an actual
Cutting time for the 5 broaches of 4 min. Io Sec.
The complete set of broaches is shown in Fig. 127, and the exact propor-
tions are given in Fig. 130. The practice here, it will be observed, is
to make the broaches rather short, the tooth length for the hexagon broaches
being 27 in. and for the six-spline only 15 in. This not only makes them
easier to make, harden and handle, but quicker work can be done with them,
as five of these broaches can be run through the work in less time than
three long ones. -
Right here is a good place to bring out the fact that in designing all
broaches, it should be borne in mind not to have the teeth so closely spaced
that too many of them will be in the work at the same time. If there are, too
much power will be required to draw the broach through, resulting in slower
and more costly production and danger of stalling the machine or pulling
the broach in two. Closely spaced teeth also increase the danger of clogging
with chips. These are points often overlooked by those designing broaches
for special work.
MACHINING THE BROACHES
The practice at the Alco shop is to center bars of steel of the proper size,
then turn and cut the teeth in a lathe, the larger sizes not even needing a
steady-rest, but the small slender broaches being either supported in a steady-
rest or by a follower.
A very important point in making broaches for hard steel, like the gears
shown, is to undercut the teeth about 2 deg. and form a smooth fillet at the
root of the teeth, so as to give the chip a nice curl and not merely Scrape
the metal off. As a general rule, about o.o.o.2 in. is allowed as the increase
I34 BROACHES AND BROACHING
in size per tooth. This allows the tooth to “bite” properly, even when
slightly dull.
After the teeth are cut, they are shaped in a miller, using a dividing head
and a tail center to hold the broach. About o.o.2 in. is allowed on the diam-
eter for grinding, and on the spline broaches, about o.o.15 in. is allowed on
the sides.
A BUTTON BROACH
A rather peculiar looking broach is shown in Fig. 131. This is called a
button broach, and is used to run through a six-spline gear after broaching,
to remove or burnish out any burrs or unevenness, so that the “bores”
will all be of exact size. It is not intended primarily to remove any metal;
but to provide against possible excessive pressure caused by too much
metal, two scraping teeth are provided at A. The exact proportions of the
type of broach are given in Fig. I32.
SECURING CLEARANCE IN SLIDING GEAR SPLINES
Fig. 133A shows the sliding gears and the main shaft of the transmission.
This, it will be seen, has three feathers its whole length, on which the sliding
gears move and by which they are driven. A close inspection of the end
view, showing where the shaft comes through the front gear, will show a
plan of providing clearances on broached work, which avoids a large amount
of hand work in draw filing corners and in assembling. These clearances
are shown at A and B.
It will be seen readily from this, that a small clearance tooth is raised on
each of the cutting portions of the broach, in order to provide the clearances
shown and avoid any tendency of binding at the corners. The same effect
is produced in the transmission main shaft by having similar projections on
the milling cutter in order to produce the groove B shown and afford clear-
ance for the inside corners of the broached gear. By this method an ex-
tremely small allowance can be made for clearance when the gear is sliding
on the shaft, and a first-class fit can be secured without hand work of any
kind.
DESIGN OF SPLINE BROACHES
Much that has been said of the solid type of double-keyway broaches is
applicable to spline broaches. The main point that has to be considered
here is the best method for a proper distribution of the work. There are
Several ways of designing the teeth, and of these methods two will be dis-
cussed. First, the splined teeth of the broaches may be made all one width;
that is, if it is desired to have the finished spline 36 in. wide, then all the
broach teeth will be made to this width or just as much larger as will give
a splined hole the keyways of which will be slightly under the predetermined
maximum limit.
THE DESIGN OF PULL BROACHES I35
There are several objections to this method. In pulling out the hole,
particularly if the broaches are loaded up-and this must be done, if it is
A
A
Fig. 131.-A button broach.
desired to get the maximum output—there will certainly be occasional drags
along the side of the spline. Further, with very tough steels there may be
Tooſ Sfeeſ, Harden *.003" -0/6"/ºad
Fig. 132,-Button-broach dimensions.
undesirable drags at the end; sometimes pieces will pull out. Again, with
this method all the teeth must be of exactly the same width; and the divid-
- - - -
FIG. I.33A-Transmission gears, showing corner clearance on splined shaft.
ing of the teeth—that is, their angular spacing—must be accurate, or ridges
will show on the work.






I 36 BROACHES AND BROACHING
This extreme accuracy applied to every broach in the set adds to the
expense of making them. Apart from this, the question of holding the work
to close limits will be more difficult of attainment because of these ridges,
and the fact that all the broaches are of the same width generally results in
keyways that are more or less tapering toward the hole.
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Grinding the Broach
A Diamond Holder
FIG. I.33 B.-Machine operations on spline broaches.
The alternative method is to make the spline teeth of different widths.
Suppose that a set of broaches are to be designed to give a hole suitable for
a 2 by 134-in. shaft having eight 36-in. splines. Then the broach teeth will
be as follows. Assume that five short broaches are required. The first
four broaches should be so proportioned as to diameter that they will bring
out the splineways to the full depth, the fifth broach being used to bring them







THE DESIGN OF PULL BROACHES I37
out to the required width; that is, the fifth broach should just take a light
cut up each side of the splineways.
To insure that the roughing broaches work easily, without undue fric-
tion on the unrelieved sides of the teeth, it is best to have each successive
broach with slightly narrower teeth than the preceding one. The sizes that
will work successfully for such a set of broaches are given in the diagram,
Fig. I33B, which shows the teeth exaggerated and Superimposed. Some
designers give the finishing broach more to do on either side, but I have found
that 364 in. per side produces cleaner results together with longer broach life.
Of the many different ways of arranging the roughing broaches so as to
take a maximum cut for any given material without loss of efficiency there
is no other so effective as that of staggering the teeth of the broach; that is,
arranging for successive teeth to cut alternately at the center and corners of
the splineway.
The best practice is to have only the last few teeth of the broach, which
bring the hole out to the full depth, left unnotched. These unnotched teeth
should never have much load and should only be used to give an even ap-
pearance to the top of the splineway.
ADVANTAGE OF NOTCHED TEETH
The greatest benefit derived from the system of notched teeth is found
in the fact that less room is required for the chips. It is generally recognized
that the longer the hole that has to be broached the wider must be the spac-
ing of the teeth. There are two reasons for this: First, the total load on the
broach may be more than the cotter will stand without shearing, if too many
teeth are in action together without reducing the load per tooth; Secondly,
the longer the hole for any given load per tooth the greater the required
chip space. Now, for maximum life of the broach a minimum load per tooth
is necessary, and consequently for any given length of broach the aim must
be to divide the work among the largest number of teeth that is consistent
with ample chip space. This, then, is why the notched-tooth system is so
effective. *
When the teeth are not notched—that is, the chip is full width—the
chips pile up in front of the cutting tooth and only about one-half of the
Space provided is actually used to accommodate chips. On the other hand,
when the teeth are notched, the chips do not stay in front of the teeth, but
will fall on either side. Thus, for any given load of tooth and length of hole
a shorter pitch can be used for notched teeth than for teeth that are of full
width. . This means fewer broaches to the set, or the same number of broaches
may be provided and the load per tooth decreased, thus insuring a longer life.
STAGGERING THE TEETH
The staggering of the teeth may be accomplished in several ways, but
the following methods have been well tried out and can be recommended as
I38 BROACHES AND BROACHING
easy of application and rapid in action. The corner may be quickly removed
by means of a pair of straddle mills, as illustrated in Fig. 133 B.
The mills are set at the correct distance apart to take off two corners at
once, as shown at A. As the width of the tooth that is left should be con-
stant, then as the height of the teeth is gradually increasing by a definite
amount, the knee of the miller must be lowered to allow for this difference
in height. For this reason it is best to notch all the corners of each tooth be-
fore proceeding to the remaining teeth. The method is as follows: Set the
cutters central over the first tooth and take a trial cut; lower the knee and
divide; then follow the same process all around, noting the setting of the
knee.
If the corners are notched sufficiently, move the table of the miller a distance
equal to two pitches and repeat the notching, taking care that at each suc-
cessive row of teeth the setting of the knee is diminished by the amount of
the rise of the teeth. This small amount may be calculated, or it can easily
be determined by trial on the first few teeth. By this method the cutting
portions of the teeth are of approximately the same width, and this is a very
important factor in the cutting efficiency of the broaches.
One setting of the mills—as to distance apart—will do for the set of
broaches, because although the chordal distance between each successive
set of corners is increased, the width of the straddle mills will cover this
difference.
USING 45-DEG. ANGLE MILLS
Another way is to use two 45-deg. angle mills, but the disadvantage of
this method is that on the first and second broach, where the height of the
tooth is small, unless the mills are quite narrow, enough is not taken off the
corner of the tooth. With a pair of mills made specially for the job this
disadvantage disappears, but it entails a change in width–spacing of the
cutters—to complete a set of broaches.
The groove in the center of the teeth—even numbers—may be cut in a
similar manner, but here the varying chordal distance will have its effect.
Consequently, the setting of the two half-round cutters should be altered
for each broach, as the groove must be approximately central. If the
broaches have only a few splines—say of the order of four or five—it will be
best to put this central groove in with a single cutter, as shown dotted at B.
For an eight-spline broach the difference apart of center of the teeth is negli-
gible. For broaches having narrow splines this central groove is best put in
with a narrow grinding wheel, dressed to the required shape, after the
broaches are hardened and finish-ground on their periphery.
There is another operation in connection with making spline broaches
that is worthy of mention, because if it is not properly attended to, the result
will be poor holes. Spline broaches work best in holes that are a good fit on
the broach bottom. Should the hole be oversize, then the weight of the work
THE DESIGN OF PULL BROACHES I39
would take it over to one side of the broach, with the consequence that the
spacing of the splines would not be accurate with the axis of the work. When
the next broach is put through, the work may be put on the other way up;
and this broach would then probably bind along the side of the spline.
However, the worst feature of badly sized holes is that occasionally some
will be small, and then the front of the grinding portion of each tooth may try
to take a cut. As there is no relief on this part, naturally, the result of a
tight hole is almost invariably a bad tear. For this reason holes that have
to be broached with spline broaches should be kept to fairly close limits. As
a large number of splined holes have to be ground out after hardening, there
is a tendency in such cases to allow a wider limit in the hole than is desirable;
but for the reasons given, it is unwise, and it is sound practice to hold all
such holes between grinding size and minus two-thousandths of an inch.
With such limits the broaches must be made so that the minus-sized holes
will go on.
To prevent any possibility of the guide portions of the teeth tearing,
the front of each guide should be rounded or beveled off. This can be
readily accomplished by dropping a small milling cutter—of the right
curvature—on the front of each guide, as shown in the section through
broach (Fig. 133B). This puts a distinct bevel on the front edge and entirely
prevents any tendency to drag. The beveling done by the cutter may be
supplemented by forming a radius with a file; but this is a slow process,
and unless the rounding off is well done, it will disappear when the guide
portion of the broach is ground.
GRINDING SPLINE BROACHES
To grind spline broaches, no special machinery is needed, but accurate
and careful methods are necessary. Where spline broaches are required, a
Bath spline grinder is most useful. When such a machine is available,
the grinding of the broaches is considerably simplified. On this machine
there is provision for dividing and indexing the broaches, and there is also an
attachment for giving the grinding wheel the correct curve. The wheel-
truing attachment will also bring the sides of the wheel to the shape required
to grind the sides of the splines, but in the case of broaches the wheel should
never be allowed to work on the body of the broach and the sides of the teeth
at the same time.
The reason for this is as follows: When the grinding wheel passes along
the broach, there is sure to be some slight springing of the broach. As the
wheel passes off a tooth, the broach rises slightly, with the result that if the
grinding wheel is grinding the sides of the teeth, these will be somewhat
smaller back and front than in the middle; that is, there will be a high place
on the center of the tooth. This means of course that the teeth will bind in
passing through the work and will need to be relieved before they will pro-
I40 BROACHES AND BROACHING
duce the desired result. The best way to grind the broaches is to grind the
body first, as shown at A, in lower part of Fig. 133B, and then to grind
each side of the teeth with the flat side of a wheel, as shown at B.
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After grinding one side of all the teeth with the wheel in the position
indicated by the full lines, the wheel should be reset to the position shown
dotted and the other side of the teeth ground. As there is a possibility of
Some of the teeth being scant—owing to distortion in hardening—it is always








THE DESIGN OF PULL BROACHES I4 I
advisable to go over the teeth twice, first roughing them down to within a
few thousandths of an inch of size, then with a nice true clean-cutting wheel
bringing them to size.
But while a Bath spline grinder is a convenience in making broaches,
it is not absolutely necessary, because the grinding may be done on any tool
grinder that has a table of sufficient length. The requirements are means
of accurately indexing the broach and some arrangement for turning the wheel
to the desired curve for the body. The dividing head of a miller may be
readily adapted to the grinder for indexing the broach. The diamond holder
shown in Fig. 133B, although crude, will true the wheel to the desired
radius.
In this device the bar A is a piece of cold-rolled steel drilled and tapped
at one end for the screw B, into which a small diamond is set. When the
diamond is set to the required radius, the grubscrew Clocks it in position.
The length of the stock A should be the same as that of the broaches to be
ground. There is then no need to move the centers of the dividing head in
order to use the diamond. In utilizing this device the broach is removed
from the centers and replaced by the wheel-truing fixture. The grinding
wheel is brought directly over the diamond and the radius is swept out by
oscillating the diamond by means of the pin D, driven into the other end of
the stock. -
In Fig. 134 is shown a standard for spline broaches. It will be noticed
that a short plain piece is left on the end of the broach. This is shown to a
larger scale at A, Fig. 135. Both in making the broaches and in subsequently
grinding them this plain portion will be found convenient for the application
of the carrier to drive them. When broaches are made without this piece,
the end teeth frequently get damaged by the carrier.
To prevent mistakes it is best to paste on the drawing an end view showing
the correct number of splines. An auxiliary tracing should be made, show-
ing all these end views, to the same scale as the standard sheet; and one of
the blueprints from this can be cut up and the correct view pasted in position.
The auxiliary sheet would look like Fig. 136. The slope for the back of the
tooth may be expressed as a dimension, but it has been found more con-
venient to express it as an angle. This really depends on the method of
turning the broaches.
The method used by the writer is shown diagrammatically in Fig. 137 and is
as follows: After the broaches are turned, the teeth are spaced by means of a
parting tool taken down to the full root depth. After this slope is put on
by means of the tool A, which is fed in the correct angular direction, the slide
of the lathe is set to the angle given on the standard sheet. The final
operation on the teeth, which is turning the Io-deg. undercut on the face
of the teeth, is performed as indicated by the tool which is fed in at Io
deg. -
A table of dimensions may be filled out in various ways. One method
I42
BROACHES AND BROACHING
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number of teeth on the broach its dimensions
may be taken directly from the table.
Another way is to figure the first tooth and
the last effective tooth, also the few idle teeth
at the end.
The method of grinding the tops of the
teeth is as follows: The last few, or idle,
teeth are ground parallel, and the first tooth
is ground to size. The grinder is then set for
a taper that will join these teeth in one slope.
Afterward the table of the grinder is set to
3 deg., and each tooth is backed off to a cutting
edge. By applying Prussian blue to the teeth
before starting to back them off, the relieving
can be performed expeditiously, because the
blue is distinctly visible while the work is re-
volving and forms a good guide as to when
the tooth has acquired a cutting edge. This
is of course when the blue is just about to
disappear.
The experience gained from previous sets
of broaches, taken in combination with the
conditions to be met, is the best guide in
designing new sets. Experience is always
valuable, but tabulated experiences are the
most reliable, as they do not depend on
memory. For this reason ample notes of
each set should be taken, together with the
conditions under which they worked and how
they performed. The data sheet I have used
for some years is given in Table V. It gives
the size of broach and number of splines,
number of broaches to a set, load per tooth,
and is filled in with the data of a few suc-
cessful sets.
To use this data sheet when a new set of
broaches are made, the details are entered on
the sheet. Each fresh set is given a reference
number on the data sheet, and this reference
number always prefaces any entry that is
made in regard to the operation of the
broaches, the length of the work and the
material broached. By such a procedure
THE DESIGN OF PULL BROACHES I43
all notes relating to any particular set are brought together; and used in
conjunction with the data sheet, they form a reliable guide for the design
of any subsequent set.
REPAIR AND UPKEEP OF SPLINE BROACHES
The repair and upkeep of broaches, says Walter G. Groocock, in the
American Machinist, is such an important item that the broach designer
must of necessity pay some attention to this side of the subject. It will be
readily recognized that the life of a set of broaches depends very largely on
the attention they receive after they are put to work. Consequently, the
design should be such that careful attention will prolong the life of the
broaches without any sacrifice of accuracy or utility.
Spline broaches should never have dead sharp corners on the cutting
teeth, except for the last few teeth of the finishing broach. It will always be
noticed by any close observer of broaching that the corners are the first to
fail. This, of course, is in accord with a turner’s experience with a parting
tool. If the sharp corners of the broach teeth are just rubbed off with an
oilstone so as to give about ¥100-in. radius, they will stand up much better
than if they are left quite square; and if the corners are subjected to periodical
examination and those teeth showing any signs of wear are touched up,
then the life of the broaches will be prolonged.
When working on very tough or hard materials this periodical examina-
tion is absolutely essential, because one bad tooth on a spline broach will
Soon bring disaster to other teeth near it unless some precaution is taken.
The preventive means that may be adopted are various and will naturally
depend on the disorder; but whatever the method adopted, it must be such
that no double load can fall on the teeth following. When a tooth is bad–
that is, is beyond the usual point where a local sharpening will give it a fresh
lease of life—the best thing to do is to grind it until it presents a cutting edge.
As it will not, when so treated, do any real cutting, the work it should have
done must be shared among, say, the next four teeth in order.
Thus, suppose the load per tooth on a broach is o.o.o.4 in. and a tooth
has failed; then instead of the next tooth to it having to take o.o.o.8 in., as it
would have to do if the broach was left in its damaged condition, the next
four teeth to the damaged one should be ground so that each of them will
take a cut of o.o.o.5 in. The question may be asked, If the damaged tooth
will not cut, why grind it to a cutting edge? -
Teeth that have to be ground below the cutting line should always be
ground so as to cut, because there is always a distinct possibility of pieces
of chip getting in front of them; and if the tooth has a cutting edge, no harm
will result. On the other hand, should it be just roughly rounded off and
a chip get on it, a bad rub will result in the broach getting crowded to the
opposite side of the hole, with the possibility of serious damage.
I44 BROACHES AND BROACHING
REASON FOR GRINDING BAD TEETH
There is yet another very good reason why the bad teeth should be care-
fully ground to a cutting edge and not merely rounded off. Accidents will
happen; and after a time, particularly with spline broaches working on tough
alloy steels, so many of the teeth get chipped and show signs of failing at
the corners that it is necessary to do something that will keep the broaches
in Service. This may be accomplished in several ways; for instance, another
broach may be made to replace the damaged one, or an extra broach may be
put in the roughing set and by so doing reduce the load per tooth.
To take a concrete case for an example, suppose a set of broaches used for
pulling out a 2 by 1%-in. six-splined hole is in bad order. There are four
broaches to the set (roughing), each having 32 effective teeth. Then the
diameter increase per tooth would be i. = o.o.o.2 in. per tooth Or, say,
}í6 in. per broach. Now if it is decided to have only four broaches to a set,
then a new No. 4 broach must be made; and Nos. 2, 3 and 4 must be ground
respectively to the sizes required for Nos. 1, 2 and 3. Properly case-hardened
broaches should always have a good 316 in. of case, and consequently by
reducing the broaches as mentioned the case-hardening will have been ground
only about halfway through.
If, on the other hand, the broaches are thought to have been overloaded
and it is decided to introduce another broach to ease the load per tooth,
then only sufficient should be ground from No. 1 to make it clean up; and serv-
ing the others the same quite possibly would only need about half the teeth
on the additional broach to cut, leaving the other half available for subse-
quent grindings to bring the Corners into good condition.
THE QUESTION OF RESERVE TEETH
The question of having a reserve of teeth is one that is closely allied to
the design of the broaches. All new broaches should have several teeth
at the back end that do not cut when first used, and these teeth will be avail-
able when grinding takes place. To illustrate this point, take the case of a
broach with 36 teeth, the total increase in diameter of which is to be 946 in.
Now the broaches may be made by spreading this work over the whole of
the 36 teeth, or o.o.o.2 in. per tooth can be taken and leave four teeth idle.
This latter is to be preferred, because when the corners are bad the face of
the teeth can be ground; and this will reduce their diameter so that after a
few grinds it will be found that there are only three idle teeth.
Apart from this orthodox grinding of the face of the teeth the corners
may, through mishandling, wear, etc., get into such a poor condition as to
necessitate grinding the tops of the teeth, as mentioned before. If three
idle teeth are in reserve, this means that the diameter of all the bad teeth
THE DESIGN OF PULL BROACHES I45
can be reduced by oooo in.—quite an appreciable amount to grind off—and
still have the broach the same size at its finishing end. For this reason alone,
short spline broaches should never be designed to have less than four idle
teeth each, and on finer pitches six teeth would be preferable.
Another point in connection with the making of broaches, which will
materially assist in their maintenance, is this: After the broaches have been
in use for some time and require sharpening, they will be found to be sprung
out of truth. If the sharpening is to be just a local grinding of the face, this
error from truth will not matter; but should it be desired to grind the tops of
the teeth, then naturally the broach must run true before the wheel can be
applied to it. -
If, when the broaches are made, one of the chip grooves about the middle
of the broach is also ground concentric with the tops of the teeth, then when
it is desired to grind the tops after use, the work can be kept running true on
the grinder by running on a small steady-rest.
BROACHES FOR MOTORCYCLE GEARS
The broaches shown at A, B, C and D, Fig. 138, are used at the factory
of the Pierce Cycle Co., Buffalo, N. Y., for the purpose of broaching quad-
ruple keys in steel gears used in motorcycles.
Owing to the toughness of the steel gears, and the fact that sharp-cornered
keys are wanted, four broaches are used. The broach A cuts away the
greater part of the metal between the keys and has 32 teeth of o.5o-in. pitch,
which increase in diameter by o.oos in. each, from start to finish, except the
last, which is only o.o.o.3 in. larger. The chip clearance is o.375 in. wide and
has an angle of 30 deg. back of the tooth, and is slightly undercut at the cut-
ting edge to curl the chips. This leaves a land back of the cutting edge
o. 125 in. in width.
The main tooth dimensions of B and C are the same as for A, except
that the teeth increase only o.o.o.25 in. in diameter. The finishing broach
D is considerably shorter and less expensive to make when it gets worn
undersize, there being only II teeth of o.o.5-in. pitch, having a land o. 187
in width. The chip clearance at the back is 30 deg. and there is Io deg.
undercut to the cutting edge.
The gear blanks, in this case were 2 in. thick and made of 3% per cent.
nickel steel, o.20 to o.30 point carbon. -
DESIGN OF DIAGONAL-TOOTH BROACHES
The broaches here shown represent the shop practice of the Davis Boring
Tool Co., St. Louis, Mo., and are the ones used in the machine shown in
Fig. 62. In Fig. 139, A is a very large broach for finishing the ends of rec-
tangular holes. E and B are a pair used for finishing the ends and sides of
IO
I46
BROACHING
BROACHES AND
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THE DESIGN OF PULL BROACHES
147
B
|E.
F C
Fig. 139.-Diagonal-tooth broaches for rectangular holes.
-
\
\
\
V
V
º 3"Undercut
s"Back Slope
§
|
+=
side of Broach.” *** * *
7eefhan Božh Sides on Edge of Side cuffing Broach
Fig. 140.-Proportion of diagonal-tooth broaches.




148 BROACHES AND BROACHING
a smaller hole of the same shape. F and C, and G and D, are also pairs used
for the same purpose. Details of the design of
these broaches are given in Fig. 140.
The broaches are made of both high-speed and
carbon steel, the latter being preferred for accurate
finishing, as it keeps a keen edge longer. The
teeth are undercut and diagonal. The opposed
sets of cutting teeth are balanced to prevent the
tendency to creep. The tendency to chatter, so
troublesome in many cases, is overcome by differ-
ential spacing of the teeth, in addition to the shear-
ing angle. The sizes used vary from 34 by 1916
in. to I by 3%. 6 in. in cross-section, and from 16.
to 24 in. in cutting length. The main proportions
of the teeth are the same for all sizes, as can be
seen from Fig. 140. It will also be seen that the
angle gives a shearing cut of great efficiency in
steel, and the undercut curls the chip nicely. The
taper per foot varies somewhat, but is usually
about o.o.15 in. for the roughing, and o.o.o.9 in. for
the finishing broaches.
ECEY-SLOT BROACH
The broach and sample of work shown in Fig.
141 were first shown in the American Machinist
iſ ºntº; April 3, 1903. With broaches of this type, slots
|
of all sorts of shapes may be made from the com-
º plicated paracentric slots of the Yale locks to simple
| i curves or the common straight slots. When made
| of thin saw metal, a heavier back is used to pre-
vent springing or buckling on the cut. In the illus-
tration a piece of work in position for the broach
to start the slot is shown at A. A broach of this
character must naturally be rather long in order to
have slope enough to cut the slot at one pass.
No exact details of the tooth spacing or other
details of this broach are obtainable, but the prin-
ciple will be easily understood by any mechanic.
i.
º
|||}|{
|| || i
INSERTED–TOOTH BROACHES
As a general rule, inserted-tooth broaches are
Fig. 141–Broach for cut- unsatisfactory, but two broaches are shown in Fig.
ting crooked key slot. 142 which are used in one of the plants of the


THE DESIGN OF PULL BROACHES 140
International Harvester Co., to broach keyways in heavy traction-engine
flywheels. The bodies of these broaches are made of machine steel, and the
cutter blades are inserted in slots milled in the bodies. The one at the back
has staggered teeth, made by inserting two blades in the same slot side by
side, but with the teeth set as shown.
Fig. 142.-Two inserted-tooth broaches.
AN ADJUSTABLE BROACH
E. A. Suverkrop writes as follows:
A Colt automatic-pistol stock, the hole in which is finished by broaching, is
shown at A, Fig. 143. Considerable trouble was at first encountered in broaching
these pieces. Three sides of the hole are finished, while the fourth, which is left
Fig. 143.-The work and the broach.
half-round as it comes from the Pratt & Whitney slot miller, acts as a guide or bear-
ing for the fourth side of the broach, which has no teeth.
The original broaches were made with teeth at right angles to the direction of the
cut and gave poor results. The spaces became choked with cuttings and sometimes


I5o BROACHES AND BROACHING
the work was torn to pieces by the broach. The broach shown in Figs. 143 and
144, was then made. In it the teeth are at an angle giving a shearing cut. A
tapered gib B is fitted at the back end of the broach and can be adjusted by the
screw C to compensate for the wear of the teeth and thus retain the depth of the
slot in the work. This dimension is important.
With these broaches the operator can turn out 200 pistol stocks a day. One
broach has finished as high as Sooo pieces.
BROACH HOLDERS OR COUPLINGS
There are numerous ways of coupling the broach shank to the drawhead
of the machine, the simplest being a sleeve into which the end of the broach
- -
Fig. 144-Showing the wedge adjustment.
shank is slipped and fastened by means of a cotter pin run down through
slots in the sleeve and broach end. On many small broaches, an adapter
is screwed onto the end of the shank, the adapter fitting the sleeve on the
drawhead. The use of this kind of an adapter makes it necessary to only
have one adapter for a number of sizes of broaches, the shanks of these
broaches all being threaded alike. As a rule, an adapter of this kind which
is made to screw onto the end of the broach, should have some means of
locking or clamping it securely to the thread to prevent any tendency to
loosen or twist as the broach is pulled through the work. This can be done


THE DESIGN OF PULL BROACHES I51
by splitting the threaded sleeve or nut and using a clamping collar with a
setscrew in it, placed over the end of the sleeve. Another but not such a
satisfactory way for commercial work is to use one or more setscrews in the
sleeve itself, the ends of the setscrews being “padded” with brass where
they come into contact with the thread of the broach shank. If any “float”
is required, it can be given by having the cotter a loose fit in the coupling
slot.
Several kinds of couplings have already been indicated, and two shown
in Figs. 39 and 111 respectively. The first shows the split-cotter type and
the second the toothed-wedge type, and need no further description here.
Two other kinds of couplings are shown in Fig. 145. The one at the right
is a modification of the split-cotter type and is used for broaches with round
shanks notched on each side, and when in use is fastened to the draw spindle
with the square end outward. The slide is then dropped down till the round
part of the slot is opposite the hole in the square block. The notched shank
of the broach is now inserted and the slide allowed to drop down, the rec-
tangular slot of the slide fitting over the notched place in the shank, locking
it securely to the spindle.
The other holder is used for keyway broaches made of a single bar of
steel of rectangular cross-section. In order to use this type of holder, the
draw spindle must either be grooved all around close to the end, or else
fitted with a cap or adapter turned down on the end and grooved to suit.
The lock itself consists of three parts—two semicircular pieces and a collar.
But one groove is cut in the flat broach shank, and one of the semicircular
pieces has a key running crosswise, that fits this groove. The opposite
end of both pieces is chambered out, and has a circular key in it to fit the
groove on the draw spindle. In using this holder, the collar, shown in the
middle, is slipped on over the draw spindle, the two semicircular pieces are
placed together over the end with the broach shank between them, and then

152 BROACHES AND BROACHING
the collar is slipped over all, locking broach and draw spindle together
securely, but allowing a certain amount of play, which is essential in practi-
cally all holders used for this purpose.
At the left in this cut, is shown the end of a cutter-bar or keyway broach
resting in the slot of a work bushing, used to guide the tool while cutting.
FIG. I.46.-An eccentric coupling lock.
AN ECCENTRIC LOCK
Another quick-acting and very satisfactory coupling lock is shown in
Fig. 146 and in detail in Fig. 147. This type was developed in the shop of
Brown & Sharpe, Providence, R. I., and is used for the broaches shown in
Fig. 123, which have a rounded recess milled in one side of the shank. The
• *-
Aºi -->
Fºf Machine
k
/
-
i.
s
FIG. I.47-Details of an eccentric lock.
holder is held in the drawhead by means of a pin through the shank, and is
positioned by a setscrew. The eccentric is operated by a T-wrench, and
stop pins on the collar of the eccentric limit its movement to the on and off
positions.
On some machines a threaded sleeve is screwed directly into the draw-
head. These sleeves are split and threaded to receive the coupling proper,



THE DESIGN OF PULL BROACHES I53
which is attached to the end of the broach shank. The drawhead and
sleeve made by the Lapointe Machine Tool Co., shown in Fig. 148 illustrate
this method. For use in this type of head sleeve, the couplings used in the
Alco shop are especially adapted. These couplings are shown in Fig. 149.
FIG. I.48.-Threaded draw-head sleeve.
In this shop there are two common types of locks used to fasten the broach
shank into the coupling, one is the straight and the other the forked key
the couplings for these being shown at A and B respectively. The former
is usually used on large broaches with round shanks of sufficient size and
FIG. I.49.-Various types of couplings.
strength to stand having a slot cut through them for the key. The other
type is used for smaller broaches having a notch on each side of the shank
near the end.
The coupling C is used for three different keyway broaches of rectangular
cross-section. The coupling shown at D was designed at the Alco shop to


I54 BROACHES AND BROACHING
hold very small broaches which it was undesirable to either slot or notch.
The holding device consists of two jaws, like chuck jaws, set into a turned
block, and operated by a hand screw, as shown.
WORK BUSHINGS AND WORK-HOLDING FIXTURES
Besides the work bushings and holders for the common run of work, there
are numerous indexing work holders for special or unusual jobs, but as these
usually have to be designed specially in each case and fitted to the face-
plate of the machine, no further mention need be made of them except
what has already been touched upon in a general way. A number of
bushings are shown in Fig. 150. The one at A is used to cut two keyways
at right angles to each other. Two broaches are not used, but one keyway
is broached, then the piece is turned till the keyway is coincident with the
blank slot, after which a key is thrust in to hold the work while the other
keyway is broached.
This differs only slightly from the one shown at A, Fig. III, which can
be used only after the keyway is broached on another holder. Again refer-
ring to Fig. 150, the bushings B, C and D hold work with taper holes, and
E with a straight round hole. The bushing F is for locating a small lever
in which a square hole is broached, the lever being placed lengthwise of the
groove across the end of the bushing. Only part of H shows, the other
part being the same as the part shown. This is used to locate a certain
size gear, the teeth of which fit the guides on the inside of the uprights.
Another work holder for gears is shown in Fig. 151. The keyways cut
with the gear held on this bushing will have a definite relation to the teeth,
one of which fits between the two teeth at A on the locating block. This
block is adjustable, so that gears of different diameters may be placed on it.
GEAR HOLDING AND MARKING FIXTURE
Where a chain or set of gears to be keyseated, bear a certain definite
relation to each other when assembled, it is a good plan to place a mark on
each near the teeth to assist in the setting in the first assembly and also in
any future operations.
The superintendent of Haberer & Co., Cincinnati, Ohio, has designed a
set of fixtures, for marking each gear used in their car, not only in definite
relation to the keyway cut, but also to the particular meshing tooth. Fig.
I52 shows three of these fixtures used for crank, camshaft and magneto
gears. The gears are in each instance slipped into place over slotted work
bushings in the center, through which the broach moves. A dog or locking
pin, fitting between two of the teeth in each gear, holds them in place. A
single marking punch, carried in a hinged holder, is used on each of the two
left-hand fixtures. The right-hand one has two of these marking punches.
THE DESIGN OF PULL BROACHES I55
It will be seen that a light tap on the marking punches with a hammer,
before the broached gears are removed, will leave a guiding mark, showing
how to set them when assembling. This system is applicable to many
Fig. 150.-Several kinds of work holder.
jobs of duplicate work, and may be used on almost any broaching machine,
of either the push or pull type.
Fig. 151-Adjustable holder for spur gears.
A MOTOR-CAM FIXTURE
A little fixture used for holding cams while broaching the keyway is
shown in Fig. 153. The use of a fixture like this insures the keyway being


156 BROACHES AND BROACHING
cut in the proper relation to the rise of the cam. The part in which the
broach slides is an ordinary work bushing. Doweled to this is a plate
FIG. I53.-Cam fixture.
carrying a slide with a V-cut in the lower end. This slide is moved by means
of the thumb-screw shown, so that when the cam is slipped into place, a
slight turn of the screw will lock it in position.

CHAPTER VI
THE DESIGN OF PUSH BROACHES
While the formulas, tables and rules given for pull broaches apply in a
general way to the push type as far as the pitch and contour of the teeth is
concerned, there is considerable difference in the length of the broach itself,
due largely to the fact that a push broach must be made stiff enough to not
Spring or buckle as it is forced through the work. Probably the first real
broaches made were push broaches, but at present they are not nearly so ex-
tensively used as the pull type. Definite rules for the design of push broaches
that will fit every occasion are not available. A prominent manufacturer
and engineer, who has probably had more to do with push-broaching work
than any other one man, in answer to a question put to him 2 or 3 years
ago regarding a formula for push-broach teeth, wrote as follows:
We started out years ago with formulas but various conditions caused these
to be modified in such an empirical fashion that there is little left that could be
called a formula. As a matter of fact, we have learned by experience what is
required to meet certain conditions and the broaches are designed in that way.
We find that the depth of cut which of course is a function of the pitch can be
very materially increased in the case of square broaches as the corner is approached.
The pitch of the entire set is maintained constant as a matter of convenience, while
the amount of cut taken per tooth is frequently as much as six times as great near
the end of the last broach as it was at the beginning of the first one. Whether or
not an empirical formula could be worked out from the figures representing our
present practice, I cannot say at the moment, not having had occasion to look the
subject up from that standpoint.
My impression is that investigation would show that the pitch of the teeth is
just about as logical as the width of keys which are used with given diameters of
shafts, that is the width and depth of keys are as you know largely a matter of
individual design, although there are several standards any one of which is not very
closely followed and have all been worked out from practice, and in any given series
of sizes the proportions in common practice do not bear any uniform relation to the
diameter of shaft with which any given size is used.
I should say offhand without investigation that the pitch of the broach teeth
would fall into the same class of data.
TABLES OF PUSH-BROACH DIMENSIONS
Fortunately we are able to give in this chapter an unusual number of
tables, compiled from actual shop practice, to guide the designer of push
I57
I58 BROACHES AND BROACHING
broaches in his work. The Spicer Manufacturing Co., Plainfield, N. J.,
does a tremendous amount of accurate broaching in connection with the
manufacture of its universal joints, and the results of its years of experience
in the design of broaches is extremely valuable. The tables, worked out
from actual practice at the Spicer shop, for machining forgings of 40-point
carbon Steel, will give first-class working data.
It will be noted that where the length of the hole varies, allowance is
made in the tooth proportions, in order to equalize to some extent the power
required to force the broach through, and in making similar broaches these
tables may be used as guides for others approximating the same dimensions.
These broaches are used in Watson-Stillman 20-ton hydraulic presses, the
average time required to force a broach through and return the ram to the
starting point being between Io and 15 sec., varying slightly with the different
sizes.
The tables for round-cornered, square broaches need little explanation
other than to call attention to the fact that the cutting teeth are all developed
on the corners, the flat sides being milled the same and not “stepped”
as usual, an advantage which will be gone into more in detail in another
article describing the making and use. Attention is also called to the ample
chip space and curve of the fillet at the root of the teeth, without which a
broach is useless in steel, and to the fact that the first, or pilot teeth, are the
same dimensions as the last teeth of the preceding broach.
On the six-spline broaches, the method of breaking up the chips by groov-
ing alternate teeth is worth noting, as well as the improved form of teeth,
which are the design of Mr. Spicer. These teeth give the maximum chip
clearance; maximum strength with the minimum of metal, allowing closer
Spacing of the teeth, and consequently less broaches to a set, to produce
accurate results, though, of course, closer-spaced teeth mean more power
to force through. The ten-spline broaches have in addition to the im-
proved form of teeth, a special design of pilot teeth which makes it easier
to start them quickly.
In the first table, the grinding allowance is as low as o.o.o.6 in., and in two
cases—the 33- and 91.6-in. Square broaches—it is o.o.1o in.; but in a majority
of cases the allowance is o.o.32 in., or approximately 364 per tooth, for both
Square and multiple-spline broaches.
In all cases, except the 3-in. size, the butt end of the broach is made
Somewhat cone-shaped, to fit the cupped end of the push pin in the press
ram, which automatically centers and lines it up, the work hole, of course,
being placed directly in line. The serial numbers of the broaches indicate
in each case the number used in a set to complete the size of hole specified.
THE DESIGN OF PUSH BROACHES
I59
§§j
7. Cuffing Teefh
TABLE VI.—DIMENSIONS OF 34-IN. SQ. BY }{6-IN. BroACHES
For Hole I in. Long
Y- | º
º
s:
|
Izathe dimensions Grinding dimensions
No.
Ol. b C A. B
in. in. in. ft. in. in.
A-I o. 256 o. 26o 1%4 O. 25O O. 254
A-2 o. 26o o. 266 %6 O. 254 o. 26o
A-3 o. 266 O. 274 316 o. 26o o. 268
A-4 O. 274. o. 284 1364 o. 268 o. 278
A-5 o. 284 O. 295 1364 o. 278 o. 289
A-6 O. 295 O. 3O7 %2 o. 289 O. 3OI
A-7 O. 3O7 o. 328 %2 O. 3OI O. 32.2
s /O Cu++ing Teefh
Sºx-(; C ſ G
Sº H ſº -
&s ! ...f4. & i.
- g •l t .. #/? - * . * { * , , , , ,”
K-; ...J.; Laº gº. *off 27%. * **
|< - ------- - 3” ~~~~~ ----------->
TABLE VII.—DIMENSIONS OF '946-IN. SQ. By 2%4-IN. BROACHES
For Hole 96 In. Long
Lathe dimensions Grinding dimensions
No. -- - - -
..a b © C g A. B
1I]. 111. 111. 111. 111. 111.
AB-I O. 342 O. 349 1364 O. 322 O. 329
AB-2 O. 349 o. 361 1364 O. 329 O. 34I
AB-3 o. 361 O. 377 % O. 34.I O. 357
AB-4 O. 377 O. 397 1%4 O. 357 O. 377
AB-5 O. 397 O. 422 %2 O. 377 O. 4O2
AB-6 O. 422 O. 452 1%2 O. 4O2 O. 432






I6o
BROACHES AND BROACHING
10 Cyffing Teefh
s
33 (
*\lco *: - º: º ‘.
- *f; Lafhe 'º' . . . S JAN 2.
lº - jor 25 *3
TABLE VIII.—DIMENSIONS OF 36-IN. SQ. By 3%.4-IN. BROACHES
For Hole 194 In. Long
..."; Back off 2°.
Ki
Lathe dimensions Grinding dimensions
No. |
a b . C A B
1n. 1Il. 111. }I). 1I] . 1Il.
B-I O. 4 IO O. 4I 7 %2 O. 390 O. 397
B-2 O. 4I 7 O. 429 %2 O. 397 O. 4O9
B-3 O. 429 O. 445 1964 O. 4O9 O. 425
B-4 O. 445 o. 465 %6 O. 425 O. 445
B-5 o. 465 O. 490 *}64 O. 445 O. 470
B-6 O .490 O. 5I9 1.%2 O. 470 O. 499
8 C J #fir, g_Teefh ;433°
§ t º -
Şs A.
& toº
sCO —Y — º
Sº §. | | | | |
fºr: ** > * ºr ºf
Fº - - - - 3"…~~
TABLE IX.-DIMENSIONS OF 946-IN. SQ. By 1946-IN. BROACHES
For Hole 13% In. Long
Lathe dimensions Grinding dimensions
No. - - - - - - - - - --- –
(l, b | C A B
in. in. in. 111 in. in.
D-I o. 570 o. 58o % o. 560 O. 57O
D-2 o. 58o O. 592 % O. 570 o. 582
D-3 O. 592 o. 6off 1.%2 o. 582 o. 596
D-4 o. 606 o. 623 1.%2 o. 596 o. 613
D-5 o. 623 o. 644 %6 o. 613 o. 634
D-6 o. 644 o. 670 1%2 o. 634 o. 660
D-7 o. 670 O. 7OO }% o. 660 o. 690






THE DESIGN OF PUSH BROACHES I6I
TABLE X.—DIMENSIONS OF 9%-IN. SQ. BY 34-IN. BROACHES
For Hole I In. Long
Lathe dimensions Grinding dimensions
No. ------ ------ -- - --
.a. .b - C - A. B
1Il. 111. 1Il. 111. 111. 111.
E-I o. 665 o. 7oo %6 o. 640 o. 675
*,-2 o. 700 O. 745 1.%2 o. 675 o. 72O
E-3 O. 745 O. 790 .3% O. 72O o. 765
§
§§
o —Y. –
*N sº
* -
|
Hº-
TABLE XI.-DIMENSIONS OF 34-IN. SQ. By I-IN. BROACHES
For Hole 2% In. Long
Lathe dimensions Grinding dimensions
No. - --- --
a b . C . A B
111. | 111. : 111. 111. 111. in.
|
|
F-I o. 790 o. 815 1.%2 o. 765 . O. 790
F-2 o. 815 o. 845 94.6 O. 790 o. 820
F-3 o. 845 o. 885 1.%2 o. 820 o. 86d
F-4 o,885 o. 935 % 'o. 860 O. 9 IO
*-5 O. 935 o. 985 2%2 O. 9LO o. 960
F-6 o. 985 I. O4O 2%2 o. 960 O.OI5


I I
I62 BROACHES AND BROACHING
TABLE XII.-DIMENSIONS OF 1346-IN. SQ. By 1-IN. BROACHES
For Hole 1% In. Long
Lathe dimensions
Grinding dimensions
No. –––––– –––
..a b .c A. B
1Il. 111. 111. 1Il. 1I].
|
G-I o. 868 O. 9oo 94.6 o. 843 o. 875
G-2 O. 9oo O. 94O 94.6 o. 875 o. 915
G-3 o. 940 | o. 988 % o. 915 o. 963
G-4 o. 988 | I. O45 | 1}{6 o. 963 | I. ozo
G-5 I. O45 I. Io'7 l 34 I . O2C) I o82
6 C v?fing Teefh
§
CŞ
SY
3.
* Ti tº Tº ſº. ####
K-1"> * 2° S kºk-4">44-3'-
* -8"- 3-
TABLE XIII.-DIMENSIONS OF 76-IN. SQ. BY 1316–IN. BROACHES
For Hole 5 In. Long
Lathe dimensions Grinding dimensions
No. - - - -- - - - - - - - - - - - - -
A ’ C. C A | B
in. | I Il. l Il. 111. 1 Il.
- - - - - -- - - -- - - - - -
H-I o,939 o.957 3% o,997 o.92s
H-2 O. 957 O. 975 2%6 o. 925 O. 943
H-3 o,975 o.996 2%2 o. 943 o. 964
H-4 o. 996 I . O2C) 1}{6 o. 964 o. 998
H-5 I . O2C) I. O47 1}{6 o. 988 I. OI5
H-6 I. O47 I. of 7 2%2 I. OI 5 1.045
H-7 I. O77 I. Io 7 % I. o45 I. O75
H-8 I. Io 7 I. I37 % I. O75 I. IoS
H-9 I. I37 I. 167 2%2 I. IoS I. I.35
H-Io 1, 167 I. IQ7 1316 I. 135 I. I65
H-II I. IQ7 I. 227 2%2 I. I65 I. IQ5





THE DESIGN OF PUSH BROACHES
TABLE XIV.-DIMENSIONS OF I-IN. SQ. By 1%-IN. BROACHES
For Hole 1% In. Long
Ó
ſºlº
Lathe dimensions
8 Cvijing 7ee #/7
Grinding dimensions
No
a b c A. B
111. 111. 111. 111. 111,
I-I I. O63 I . III 1}{6 I. O3I I.oz.9
I-2 I . III I. I67 % I. O79 I. I35
I-3 I. I67 I. 23.I | 1316 I. I.35 I. I99
I-4 I. 23.I I. 3O2 % I. IQQ I. 270
- 8 Coyff in a - -
§y : ; : d
S.T. |º] 2 2.
**C. 3333333333)
f/ k gºš. f” 3. *śs. gº! t
F- 㺠Lafhe # 23 rtºrs
-—º - ff - ſ
[S 8 ~T),
TABLE XV.-DIMENSIONS OF I-IN. SQ. BY 1%-IN. BROACHES
For Hole 3%. In. Long
Lathe dimensions Grinding dimensions .
No.
a ... b C A B
111. 111. 111. 111. 111.
J-I I. oG3 I. oS7 1}{6 I. O3I I. O55
J-2 I. o87 I. II.5 1}{6 I. O55 I. OS3
J-3 I. II.5 I. I.47 % I. OS3 I. II 5
J-4 I. I.47 I. I83 % I. II 5 I. I5I -
J-5 I. I83 I. 223 1%6 I. I5I I. I9 I
J-6 I. 223 I. 267 1%. 6 I. I9 I I. 235
J-7| I. 267 I. 3 I5 % I. 235 I. 283
Jº, I. 3 I5 I. 37 I % I. 283 I. 339
J-9) I. 37 I I. 427 1%. 6 1. 339 I.395






I64
BROACHES AND BROACHING
7 Cuff, na Teefh
& /T AL}^1_2^ TATW.
S . . K . & < :
TY F.A.----— CO S. . H . . … O S s r
CŞ- - T Pºl 2" lºi >|<ºriº
s | >:k’ſ ” ‘... - \- |YY | |
pf w " ; Lafhe j.- cº- | sº, sº |, 5.”
k r rºº 25 * r * * * * * *
L 8 #" … . … -->
TABLE XVI—DIMENSIONS of 1%6-IN. Sq. By 1%-IN. BROACHES
For Hole 2 In. Long
Lathe dimensions Grinding dimensions
No.
(l, b C A B
in. in. in. in. 1Il,
K-I I. 122 I. I.42 % I. O9d I . I IO
K-2 I. I.42 I. I69 % | I. I IO I. I37
K-3 I. I69 I . 2C) 2 1346 I. I37 I. I 7o
K-4 I . 2C) 2 I. 242 1346 I. I 7o I . 2 IO
K-5 I. 242 I. 282 % I . 2 IO I. 25O
K-6 I. 282 I. 322 % I. 25o I. 29O
R-7 I. 322 I. 362 1946 | I. 29O I. 33O
K-8 I. 362 I. 392 1946 I. 33O I. 360
K-9 I. 392 I. 4I 2 1946 I. 360 I. 38o
So 8 Cwffing Teefh
\, ſ -
§ -r- (-3-3 s
Sº º !.
$g, | Xº - < ! - |
ef l f Nº- a § | gy | pp. | sy fa
k}ºf # 32 La he *ā. 3-> k # >|< #">4k #">
lº 9 >
TABLE XVII.-DIMENSIONS OF 1%-IN. SQ. By 1%-IN. BROACHES
For Hole 2 In. Ilong
Lathe dimensions Grinding dimensions
No.
Ol. b C A B
in. in. in. in. in.
L-1 I. I 88 I . 2 I 2 2%2 I. I56 I. I 8o
L-2 I. 212 1. 24O 1346 I. I 8o I. 208
L-3 I. 240 I. 276 1346 I. 208 I. 24.4
L-4 I. 276 I. 32O % I. 244 I. 288
L-5 I. 32O I. 37.2 1946 I. 288 I. 34O
L-6 I. 372 I. 427 1546 I. 34O I. 395


THE DESIGN OF PUSH BROACHES
TABLE XVIII.-DIMENSIONS OF 1%-IN. SQ. By 1%-IN. BROACHES
For Hole 4%. In. Long
8 Cyffing Teefh
Lathe dimensions
Grinding dimensions
No. -º-º:
..a ... b .c A B
1Il. 111. 1Il. 1Il. 1Il.
M-I I. 187 I. 2 II 1316 I. I 55 I. I 79
M-2 I , 2 II I. 239 1316 I. I 79 I. 207
M-3 I. 239 I. 27I 2%2 I, 2O7 I. 239
M-4 I. 271 I. 3O7 % I. 239 I. 275
M-5 I. 3O7 I. 347 % I. 275 I. 3 I5
M-6 I. 347 I. 39 I 1% I. 3 I5 I. 359
M-7 I. 39 I I. 439 I I. 359 I. 4O7
M-8 I. 439 I. 493 1%2 I. 4O7 I. 461
M-9 I. 493 I. 553 1%2 I. 461 I. 52 i
TABLE XIX.-DIMENSIONS OF I}4-IN. SQ. By 1%-IN. BROACHES
For Hole 2%. In. Long
Izathe dimensions Grinding dimensions
No. }
a |b .c A B
1Il. 1Il. 111. 111. 111.
N-T I. 344 I. 376 1%. 6 I. 3I2 I. 344
N-2 I. 376 I. 4I 7 1946 | I. 344 I. 385
N-3 I. 4I 7 I. 468 I 1. 385 I , 436
N-4 I. 468 I. 527 I I. 436 I. 495
N-5 1.527 I. 597 I}í6 | 1.495 I. 565
N-6 I. 597 I. 677 I}% I. 565 I. 645



I66 BROACHES AND BROACHING
Cuffing Teefh
TABLE XX. —DIMENSIONS OF I}4-IN. SQ. By 12%2-IN. BROACHES
For Hole 4%. In. Long
Lathe dimensions Grinding dimensions
No.
0. b C A B
in. in. - in. in. in.
O-I I. 3 I3 I. 344 1946 1. 281 I. 3 I 2
O-2 I. 344 I. 375 1946 I. 3 I 2 I. 343
O-3 I. 375 I. 4II 1946 I. 343 I. 379
O-4 I. 4II I. 452 I I. 379 I. 42O
O-5 I. 452 I. 497 I I. 42O I.465
O-6 I. 497 I. 549 I}í6 I.465 I. 5 I7
O-7 I. 549 I. 607 I}{6 I. SI 7 I . 575
O-8. I. 607 I. 679, 1% I. 575 I. 647
O-9. I. 679 I. 770 1%. 6 I. 647 I. 738
sº 10 Cuffing Teefh
§ ºlº
CŞ
S [...] C g
CŞ- -
So . <<}<
*ICOx! .
k; ſ #"> 3# Lafhe
* 12". *t
TABLE XXI-DIMENSIONS OF 1%-IN. SQ. By 1%-IN. BROACHES
* For Hole 4%. In. Long
- Lathe dimensions * Grinding dimensions
No. | -
(l, t b C A | B
------ in. in. in. in. | in.
- I I. 469 I. 5O4 I I. 437 I. 472
-2 I. 5O4 I. 544 I I. 472 I. 5I 2
Q-3 I. 544 I. 589 I}{6 I. 5I 2 I. 557
Q-4 I. 589 I. 639 I}6 I. 557 I. 607
Q-5 I. 639 I. 697 1% I. 607 I. 665
Q-6 I. 697 I. 762 I}{6 I. 665 I. 73O
Q-7 I. 762 I. 837 I}4 I. 73O I. 805
Q-8 I. 837 I. 927 1946 I. 805 I.895


THE DESIGN OF PUSH BROACHES
I67
TABLE XXII.-DIMENSIONS OF I}%-IN. SQ. By 2-IN. BROACHES
12, Cvj fing Teeſh
For Hole 3 In. Long
Lathe dimensions
Grinding dimensions
No.
a b .c A B
111. 111. 111. 111. 1Il.
R-I I. 594 I. 642 I}{6 I. 562 I. 61 o
R-2 I. 642 I. 702 I}% I. 6 Io I. 670
R-3 I. 702 I. 774 I}{6 I. 670 I. 742
R-4 I. 774 I. 858 I}4 I. 742 I. 826
R-5 1.858 I. 954. 1946 I. 826 I. 922
R-6 I. 954 2. O52 I 36 I. 922 2. O2O
- O'
X A & Coffing Teefh sº
޺w 43X >, >
3.
‘ss; Y. - - e S :
| wº | *śj" 3. ſ'
Kłºk. j” > 3? Lafhe 25 Hº-1"--->|<- 1">ižić- "...si
K. 12" - -
TABLE XXIII.-DIMENSIONS OF 134-IN. SQ. By 2%-IN. BROACHES
For Hole 5 In. Long
>]
I
No.
Lathe dimensions
Grinding dimensions
a b | . C . A B
1I]. | 111. 111. 111. 111. 111.
U-I I. 842 I. 860 I}{6 I. 812 T. 830
|U-2 I. 860 I. 882 I}{6 I. 830 I. 852
U-3 I. 882 I. 909 I}4 I. 852 I. 879
U-4 I. 909 I. 940 I}4 I. 879 I. 9 IO
U-5 I. Q4O I. 976 I}{6 I. OIO I. 946
U-6 I. 976 2. or 6 I}í6 I. 946 1.986
U-7 2. or 6 2. oGI 136 1.986 2.031
U-8 2. off I 2. I IO 1% 2. O3 I 2. o&o
U-9 2 . I IO 2. I64 I}{6 2. obo 2. I34
U-Io 2. I64 2. 22.2 I}{6 2. I34 2. IQ2
U-II 2. 222 2. 285 I}% 2. IQ2 2. 255
U-I 2 2. 285 2. 353 I3% 2. 255 2. 323
U-13 2. 353 2.425 13% 2. 323 2.395
U-14 2.425 2.47O 196 2. 395 2.44O





I 68
BROACHES AND BROACHING
8 Cuffing Teefh , , 86°
-> ^
2 ſº Se2
Wy t
*
Ös
S)
Ö-
Kry
ou |
s • , |
| ºf Ås. | | |
Kºkºſ’ 3-4 Lafhe Dimension 25° F 1' >|< 1" >1% ſ’ -
Hº … 12" -, -º,-------------------~~~~ :-------->
TABLE XXIV.--DIMENSIONS OF 2-IN. SQ. By 234-IN. BROACHES
For Hole 6 In. Long
Lathe dimensions Grinding dimensions
No. --- - - - -
d b C A | B
111. 1Il. in. in. in.
W-I 2. O9 I 2. Io9 1916 2. oGI 2. O79
W-2 2. Io9 2. I27 I 1546 2. O79 2. O97
W-3 2. I27 2. I5O I3% 2. O97 2 . I 2 O
W-4 2. I5O 2. I 73 I3% 2. I2O 2. I43
W-5 2. I 73 2 . 2CO I}{6 2. I43 2. I 7o
W-6 2. 2 OO 2. 232 I Jºſé 2. 170 2. 2C 2
W-7 2. 232 2. 268 I}% 2 . 2C 2 2. 238
W-8 2. 268 2.308 I}} 2.238 2. 278
W-9 2. 308 2. 353 1946 2. 278 2. 323
W-Io 2. 353 2.403 1946 2. 323 2. 373
W-II 2.403 2.457 I 36 2.373 2. 427
W–I 2 2.457 2.5I6 I 1946 | 2.427 2.486
W-13 2. 516 2. 579 1% 2.486 2. 549
W-14 2. 570 2.645 I 1346 2.549 2. 615
W-15 2. 645 2. 717 1% 2. 615 2.687
W-I6 2.71 7 2.789 11%. 6 2.687 2.759

THE DESIGN OF PUSH BROACHES
I69
*—tr
Push Pir, 23 "Dºom.
º fy
* * * . ~ ā La #he D/rner’sſon
8 Cuffing Jeefh
/f
-- / 2
TABLE XXV.-DIMENSIONS OF 3-IN. SQ. By 4%-IN. BROACHES
For Hole 9 In. Long
Lathe dimensions
Grinding dimensions
No. - -
Ol. b C A B
in. in. in. in. in.
Y-I 3. I57 3. I 73 2% 3. I 25 3. I4. I
Y-2 3. I73 3. I90 2% 3. I4I 3. I59
Y-3 3. IQO 3. 2 II 2% 3. I 59 3. I79
Y-4 3.2 II | 3. 233 2% 3. I 79 3.2OI
Y-5 3.233 3.257 2% 6 3. 201 3 - 225
Y-6 3. 257 3.283 2% 6 3, 225 3. 25I
Y-7 3. 283 3.3 II 2% 6 3, 25I 3.279
Y-8 3. 3 II 3. 34 I 2% 6 3, 279 3. 3O9
Y-9 3. 34 I 3. 373 2% 3. 3O9 3.34. I
Y-10 3.373 3.4O7 2% 3. 34 I 3. 375
Y-II | 3,497 3. 443 2% 3. 375 3. 4 II
Y-12 3.443 3.48 I 2% 3. 4 II 3.449
Y-13 3.48 I 3. 52 I 2}{6 3. 4.49 3.489
Y-14 3. 52 I 3.565 2% 6 3. 489 3. 533
Y 15 3.565 3. 613 2% 3. 533 3. 581
Y-I6 3. 613 3. 665 2% 3. 581 3.633
Y-17 3. 665 3.72 I 2% 3.633 3.689
Y-18 3.72 I 3.781 21%. 6 3. 689 3. 749
Y-19 3. 78.I 3.845 2% 3. 749 3.813
Y. 2d 3. 845 3.9 I 7 21346 3.813 3.885
Y-2I 3.917 3,997 2% 3.885 3.965
Y-22 3. 997 3. O55 21%. 6 3.965 4. O53
Y-23 4. OS5 4. I 73 3 4. O53 4. I4 I



17o
BROACHES AND BROACHING
4/200./q 4/009
O t/4094 494 (4 do
uįüuț69ä půſuº
Aſuo po poją psoſ u0
* …
* ，
،
«»
L. • ?
&{
[ [ | ſw '&/„0Ç0’0
puſ-19 °8,9，100
||-
no ķīí tíſk| –
ſä###3| ||
## ., ！puțu||
k ;&#####||… z.…….?! Jg.，
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| -
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E4||-||-
||
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pºlysg/od u ºpuſu 624 op#32;ź%%
//poocus A320/-(n, 94 4



THE DESIGN OF PUSH BROACHES 171
TABLE XXVI.-DIMENSIONS OF 134-IN. By 12%2 Six-SPLINE BROACHES
For Hole 4%. In. Long
Lathe dimensions
No. :
Ist tooth| 2 & 3 4 & 5 6 & 7 8 & 9 Io & II | 12 & 13 | 1.4 & 15 | 16 & 17
OA-I I. 282 I. 286 I. 290 I. 294 | I. 298 || I. 302 || I. 3of I. 31 o | 1.315
OA-2 I. 3 I5 || 1 , 32O | I. 325 I. 33O I. 335 | I. 34O || I. 345 I. 35o | I. 355
OA-3 I. 355 I. 360 | 1.365 I. 370 | I. 375 | I. 38o | I .385 I.390 I.395
OA-4 l. 395 || I. 4OO I. 405 || I. 4IO | I. 4IS I. 42O | I. 425 | I. 43O | I. 435
OA-5 1.435 | I.440 | I.445 | 1.45o | I. 455 I.460 | I.465 I.470 | 1.475
OA-6 I. 475 I.48o | I. 485 I. 490 | I. 495 || I. 5oo | I. 5o5 I. 5Io | I. 515
OA-7 I. 5I5 || I. 52O | 1.525 | 1. 53O || I. 535 | I. 54O I. 545 I. 55o I. 555
OA-8 I. 555 | I. 560 | I. 565 I. 570 | 1.575 | I. 580 | I. 585 | I. 590 I. 595
OA-9 I. 595 || I. 6oo I. 605 || I. 610 | I. 615 I. 62o I. 625 | I. 63o I. 635
OA-Io I. 635 | I. 640 I. 645 I. 65o | I. 655 | I. 660 I. 665 I. 670 I. 675
OA-II I. 657 | I. 68o I. 685 | I. 690 | I. 695 | I. 7oo | I. 705 | I. 7 Io I. 715
OA-I 2 I. 7 I 5 I. 72O I. 725 | I. 73O | I. 735 | I. 74O I. 745 I. 750 | I. 754
Grinding dimensions
A
Ist tooth 2 & 3 4 & 5 6 & 7 8 & 9 Io & II as is as is as a
*316 | 1.25o | 1.254 1, 258 | 1.262 | 1.266 | 1. 270 || 1 , 274 | 1.278 I. 288
2%2 I. 283 I. 288 I. 293 | 1.298 || I. 303 || I. 308 || 1 , 313 I. 318 I. 323
% I.323 I. 328 I.333 I.338 I. 343 I. 348 || I. 353 I. 358 I. 363
1546 I. 363 I. 368 || I. 373 || I. 378 I. 383 | I .388 || I. 393 || I. 398 || I.403
*%2 | 1.403 | 1.408 | 1.413 | 1.418 | 1.423 | 1.428 | 1.433 | 1.438 | 1.443
I}62 I.443 | I. 448 || 1.453 | 1.458 I.463 | I. 468 I.473 | I.478 I. 483
I}{6 I. 483 I.488 | 1.493 | 1.498 || I. 503 I. 508 I. 513 | I. 518 I. 523
1%2 I. 523 I. 528 I. 533 I. 538 | 1.543 | I. 548 || 1 , 553 | I. 558 || I. 563
1% I. 563 | I. 568 || I. 573 || I. 578 I. 583 I. 588 || I. 593 || I. 598 || I. 603
1%2 I. 603 || I. 608 || I. 613 || I. 618 I. 623 I. 628 || 1 , 633 I. 638 I. 643
1962 I. 643 || 1 , 648 I. 653 | 1.658 I. 663 I. 668 I. 673 I. 678 I. 683
1%2 I. 683 I. 688 I. 693 I. 698 || I. 703 I. 708 || 1 , 713 || I. 718 I. 722

I72
BROACHES AND BROACHING
!/000./47
|
Č
l/282ð 40 l/{004 (S/ſ）{paqs/fod deputu 6 eqoſ iſſooſ 40 a2b +
úo 6ğuuffôø4%&ğ9 ſuo lyºppaeq ſsoſ uO·l/poolus pau-aen, 94 (Snow 22 opuns
/ ··- •-- ·\
«•!}//! W „Oſz00|--{ º.º.
gſ. Tiºpuț.10,ęz00 N :
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ſº žiūſ||| ſ |�|
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|>#962#0k|<！-- * -->|<！? ►###,#-->|<！#„oſ ºſſº, ſi ：
| < ……… ！!!!!!！4!!4! …>.|<·: ~~~. ---#21 -
|}
º puſ-/9,9f/?





THE DESIGN OF PUSH BROACHES I73
TABLE XXVII.-DIMENSIONS OF 1%. By 21%2-IN., SIX-SPLINE BROACHES
For Hole 5 In. Long
Lathe dimensions
No. ; - - -
Ist tooth 2 & 3 4 & 5 6 & 7 8 & 9 Io & II | I2 & I3 | IA & 15 | 16 & 17
UA-I I. 782 I. 787 I. 792 | 1.797 | 1.802 || I. 807 || I. 812 | 1.817 | 1.822
UA-2 I. 822 1.827 | I. 832 I. 837 I. 842 I. 847 | 1.852 | 1.857 I. 862
UA-3 1.862 | 1.867 | 1.872 | 1.877 | 1.882 | 1.887 | 1.892 | 1.897 I. 9oz
UA-4 I. 9oz I. 9o 7 || I. 912 I. 917 | I. 922 I. 927 I. 932 I. 937 I. 942
UA-5 I. 942 I. 947 | I. 952 I. 957 | I. 962 I. 967 I. 972 I. 977 | I 982
UA-6 I. 982 | I. 987 | I. 992 || I. 997 2. Ooz 2. oo7 2. OI2 2. OI7 || 2 oz.2
UA-7 2. oz 2 || 2 oz7 || 2: o32 || 2: o37 2. O42 2. O47 2. O52 2. O57 2. O62
UA-8 2. off 2 2. O67 || 2.072 || 2 of 7 || 2 o82 || 2 ob? 2. O92 || 2. O97 || 2 . Io2
UA Q 2. Io 2 || 2 . Io'7 2. II 2 2. II 7 || 2. I22 || 2. I27 2. I32 || 2. I37 2. 142
UA-IO 2. I42 2. I.47 2. I52 2. I57 | 2. I62 2. I67 2. I 72 2. 177 2. I82
UA-II 2. I82 2. I87 || 2. 192 2. I97 2. 202 || 2. 207 || 2. 212 2. 217 | 2.222
UA-I2 || 2.222 || 2. 227 | 2. 232 2. 237 2. 242 2.247 2. 252 2. 257 2.262
UA-13 || 2.262 2.267 2. 272 2.277 2.282 2. 287 2.292 2.297 || 2. 302
UA-14 2.302 2.307 2.312 2.317 2.322 2.327 2.333 2.339 2.345
UA-I5 2.345 2.351 | 2.357 2. 363 2.369 || 2.375 2.381 2.387 2.393
UA-16 || 2.393 || 2.399 || 2.405 || 2.4II 2.417 | 2.423 2.429 2.435 2.44I
Grinding dimensions
A *
is tooth 2 & 3 4 & 5 6 & 7 8 & 9 10 & #1 12 & 13 * * is to a tº
I}{6 I. 750 I. 755 || I. 760 I. 765 I. 770 I. 775 I. 78o I : 785 I. 790
I}4 I. 790 I. 795 I. 8oo 1.805 | 1.810 | 1.815 I. 820 I. 825 I. 830
1962 I. 830 I. 835 | I. 84o I. 845 I. 850 | I. 855 I. 860 | I. 865 I. 870
1946 I. 870 | 1.875 I. 88o I. 885 I. 890 I. 895 I. 9oo I. 905 || I. 9 Io
I 1.3%2 I. 9 Io I. 915 I. 920 I. 925 I. 93o I. 935 | I. 94o | I. 945 I. 95o
11%2 I. 95o I. 955 I. 960 I. 965 I. 970 I. 975 I. 98o I. 985 I. 990
1746 I. 990 I. 995 2. Ooo 2. ooš 2. Oro 2. or 5 || 2.020 2.025 2.030
I 1.5% 2 2. O3O 2. O35 | 2. O4O 2. O45 2. O5o 2. O55 2. O60 2. O65 2. O70
1*762 2.070 2.075 2.08o 2.085 2.090 2.095 2. Ioo 2. Ios 2. IIo
1%2 2. I IO 2. II5 2. I2O 2. I 25 2. I3O 2. I35 | 2. I4O 2. I45 2. I 50
14%2 2. 15o 2. 155 2. 16o 2. 165 2. 170 2. 175 2. 180 2. 185 2. 190
I5% 2. IQo 2. IQ5 || 2.2OO 2. 205 || 2. 2 Io 2. 2 I5 2. 22O 2. 225 2. 230
12%2 2. 230 2. 235 | 2.240 2.245 2.25o 2.255 2. 26o 2.265 2. 270
12%2 2. 270 2.275 2.28o 2.285 2. 290 2.295 2.301 2.307 2. 31.3
12%2 2. 3 I 3 || 2. 3 IQ 2. 325 2. 33 I 2. 337 2. 343 2. 349 2. 355 2. 361
1%2 2.361 2.367 2.373 2.379 2.385 2.391 || 2.397 2.403 2.4O9
|



I 74
BROACHES AND BROACHING
·C/1/6) [< • •
######-
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k） puue.sºi ».
t/obouq (/202 po-
;- iſſodį (suſ, uo 6ujuu/62.g
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|
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| * #1####|}
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|
|
|
palyst/od tºpuſu 6 ºq oſ iſſooſ 40 322 y
3-------
lſpoolus pau-ta, aq oſ 22-24-Ins
4–––––––s





THE DESIGN OF PUSH BROACHES I75
TABLE XXVIII.-DIMENSIONS OF 134 By 18364-IN., TEN-SPLINE BROACHES
For Hole 4%. In. Long
Lathe dimensions
No.
Ist tooth 2 & 3 4 & 5 6 & 7 8 & 9 Io & II * * * * * is I6 & 17
OA-I I. 282 I. 287 | I. 292 I. 298 || I.303 || I. 309 || I. 314 | I. 319 I. 325
OA 2 I.325 I. 330 I.336 I. 34I I. 346 I. 352 I. 357 I. 363 I. 368
OA-3 I. 368 I. 373 | I. 379 I. 384 || I. 390 I. 395 || I. 4oo | I. 406 || I. 4II
OA-4 I. 4II I. 417 | I.422 I. 427 | I. 433 I.438 I.444 I. 449 I. 454
OA-5 I. 454 I.460 I.465 I.47 I I.476 I. 481 | I .487 I. 492 I. 498
OA-6 I .498 || I. 503 I. 508 I. 514 I. 519 I. 525 I. 530 I. 535 I. 541
OA 7 I. 54I I. 546 I. 552 I. 557 I. 562 I. 568 I. 573 I. 579 | 1.585
Grinding dimensions
A |
is tooth 2 & 3 4 & 5 6 & 7 8 & 9 to & as is * * is to a tº
|
2%2 I. 25o I. 255 I. 26o | I. 266 || 1 , 271 I. 277 I. 282 I. 287 | 1.293
1546 I. 293 I. 298 I. 3o4 I. 309 I. 314 | I. 320 ! I. 325 I.33 I I.336
8%2 I.336 I. 34I I. 347 | I. 352 I. 358 I. 363 I. 368 I. 374 I. 379
1 I. 379 I. 385 I. 390 I. 395 I.40I I. 406 || I. 412 | I. 417 | I. 422
I}16 I .422 I. 428 I. 433 I. 439 I.444 I. 449 I. 455 I. 460 | I. 466
1%2 1.466 | 1.471 | 1.476 | 1.482 I .487 I. 493 I. 498 I. 503 I. 509
I}% I. 509 I. 514 I. 520 I. 525 | I. 530 I. 536 I. 54I I. 547 I. 553


I76 BROACHES AND BROACHING
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THE DESIGN OF PUSH BROACHES 177
TABLE XXIX.-DIMENsions of 1%. By 15%.4-IN., TEN-spline BRoaches
- For Hole 4%. In Long
Lathe dimensions
|* 2 & 3 4 & 5 6 & 7 8 & 9 to sº 12 & 13 | 1.4 & 15 16 & 17
SA-I I. 532 I. 537 I. 542 1.547 | 1.552 | 1.557 | 1.562 | 1.567 1.572
SA-2 I, 57.2 | 1.577 | 1.582 1.587 | 1.592 | 1.597 | 1.602 | 1.607 | 1.612
SA-3 1.612 1.617 | 1.622 1.627 | 1.632 1.637 1.642 | 1.647 1.652
SA-4 1.652 1.657 | 1.662 1.667 1.672 | 1.677 1,682 | 1.687 | 1.692
SA-5 1.692 I. 697 1.702 | 1.707 1.712 1.717 | 1.722 | 1.727 | 1.732
SA-6 I. 732 I. 737 1.742 1.747 | 1.752 1.757 I. 762 1.767. 1.772
SA-7 1.772 1.777 1.782 1.787 1,792 | 1.797 1.802 | 1.807 | 1.812
SA-8 I. 812 1.817 | 1.822 1.827 | 1.832 1.837 1.842 | 1.847 1.852
SA-0 | 1.852 1.857 1.862 1868 1.873 | 1.878 1.883 1.888 1.894
Grinding dimensions
A. - - - -
1st tooth 2 & 3 4 & 5 6 & 7 8 & 9 Io & II | 12 & 13 | 1.4 & 15 16 & 17
1}{6 1.6do | 1.5os 1.5Io 1.515 1.520 I. 525 I. 503 I. 535 | I. 540
1%2 1.549 | 1.545 1.55o 1,555 1,560 1.565 1.570 1,575 1,580
1%2 1.58o 1.585 1.590 1.595 1.6do 1.605 | 1.610 | 1.615 1.62o
1316 1,620 1.625 1.630 | 1.635 | 1.640 1.645 1.6so I. 655 1,660
1742 1.660 | 1.665 1.670 1.675 1.68o 1.685 | 1.690 | 1.695 | 1.7oo
14 1,700 1.795 1.710 | 1.715 1.720 1.725 | 1.730 1.735 | 1.74o
1942 I. 740 I. 745 1.75d 1.755 I. 760 1.765 I. 770 1.775 1.780
11%.2 1.78o 1.785 1.790 1.795 1.800 1.805 | 1.81o 1.815 1.820
1% 1.820 | 1.825 | 1.830 1,836 1.841 1.846 | 1.851 | 1.856 1.860
SQUARING THE HOLES IN UNIVERSAL JOINT FORKS
Blood Bros., Kalamazoo, Mich., make universal joint forks out of a
particularly tough steel. The holes are first rough-squared in a keyseater
Fig. 154-Push broach used for universal joint forks.
to within a few thousandths of the finish size, then a broach is forced through
in a hydraulic press, enough of the original round hole being left to act as a
guide to the pilot on the broach, which when used on this class of material,
in this way, has a tendency to twist or crowd over to one side. The type of
broach used, which is shown in Fig. 154 is about 14 in. in length, with a
2%- or 3-in. pilot and a 2-in. shank. The teeth are of Jº-in, pitch and in-
12

178 BROACHES AND BROACHING
crease in size by o.o.o.1 in. up to the last tooth which is full size and twice as
wide as the others. The face of the teeth are ground perfectly straight and
parallel with the center line of the tool, giving absolutely no clearance,
though the cutting edge is slightly hooked to give a curling chip. By giv-
ing the teeth no outside clearance the company claims that the tendency
to creep is minimized.
SIZES FOR BABBITTED BEARINGS
Table XXX compiled by Geo. Hey, gives the sizes used for broaching
out solid and split babbitted bearings, the split ones being clamped together
in pairs. He says it takes no longer to broach out a bearing than it does to
carry it to a lathe. Only one broach was used up to the 3-in. sizes, but above
that two were used. About o.o.o.2 in. oversize was allowed on each broach
for the spring of the metal.
TABLE XXX
* - –G– -— ---
* * * * - - - -
CO * *
|º L$-11 || $––
H.--—E---> - NE FEDE
º American Aſachinist
Size A B C D E F Size. A B C D E | F
3 * 0 735" O 752” 6 * 1 * 1} " 4." 2}" - 2.48S" 2 502” 12” + - | " | 3 *
#" O S60" 0 S77 fy 6” 1 / 13 * 3 * o MP 2,739 " 2. 752? 12” 2 ” 4 * 3 //
- - 2.964" | 2, 998”
17 0.9S6” 1 002” 8" | 1.4.” 14” A " 3” 2.996* | 3 002" | 12" | 2" | 4" | 3"
af w 3.233 " || 3. 249”
14" | 1 112" | 1 127" | 8" | 1.4.” | 1.4.” | #" || 3: " || 3 246" | 3.252" | 1.4.” 2" | 4" | * *
f -
// 3 486 " || 3 | 408”
13 1 236." l 252 * 8” 13 * 13 * ſh" 33 * 3 406” 3 502” 14 " 2 ” 4 * y”
* ſy 3 736" || 3 748" --mº
1; " 1 364" l 377 / 8 * 13 * 13 * fºr " 3: " 3 7.46" 3 752” 14" 2 ” 4 " A "
*/ - 3 985 " .. 3 998”
13 1 488" | 1 502" | 10” | 1.4.” 13 * 1 * 4 * 3 906” 4 002” 147 2" | 4 * | * *
, 4 236." || 4 248"
1 * * ! 739” 1 752" | 10” 14" | 13 " 3 * 4+ " 4 246" || 4 252" | 1.4.” 2" | 4" | }.”
| º - 4 486” 4 498."
2” 1 970* 2 002” 10” 14" l; ” # * 4}.” 4. 496." 4.502 * | 4 " 2% "| 4 " #"
24" | 2 236 || 2 252- . 10* || 14" | 13" | " || ||


BROACHES FOR BRONZE OR BABBITT
In writing of some of the work done in the shops of the Westinghouse
Electric & Manufacturing Co., C. B. Auel says in part:
Practically all our babbitted railway, mine, crane and industrial-motor
bearings up to 4% in. and even 5 in. diameter, when made either to standard
bores, or if special, in sufficiently large quantities, now have a broaching
operation performed upon them. Over these diameters, the cost of the
THE DESIGN OF PUSH BROACHES I 79
broach becomes too expensive for the quantities ordinarily involved and
such bearings are generally machined in the usual way. The broaching
operation may be either a “rough” or a “finish” one, or it may include both.
The operation of rough broaching simply roughs out the bore, a subsequent
operation either by a further broaching or by boring being necessary to com-
plete this part of the bearing; this second operation is termed “finish” boring.
A one-piece babbitted cast-iron armature bearing (2% by 6 in.) for a
light street-car motor, and a similar but larger babbitted-bronze bearing
(3 by 7% in.) for a heavier railway motor are regularly broached. In the
babbitting of one-piece bearings, if the oil grooves are to be cut in afterward
instead of being cast in with the babbitt, the babbitting mandrel may con-
sist of a plain round bar, slightly tapered, to permit of its being withdrawn
from the mold after the babbitt has been poured. In bearings, however,
where the oil grooves are cast in, collapsible mandrels of various types are
generally used. The mandrels are made from o.o.o.4 to o.o.20 in. Smaller in
diameter than the finished bearings, leaving this amount of babbitt plus the
clearance allowance to be removed by the broach. -
After babbitting, the mandrel and plugs are removed, the fins and any
surplus babbitt penetrating the cored holes are burned away with a hot solder-
ing iron, the oil grooves are finished off and the bearing broached in a hydrau-
lic press. A pressure of 5 to IO tons is required, depending upon the diameter
and the length of the bearing, as well as upon the hardness of the metal and
the amount removed. The actual time of broaching is very small, in general
varying from I to 2 min. The bearing is next placed upon an arbor, turned
and faced in a lathe, after which it is either profiled on the outside for a
keyway or similarly drilled for a dowel pin when it is then completed. It is
Sometimes necessary, especially when the oil grooves are cut in the lining
after babbitting, to run the broach through the bearing a second time in
order to remove any slight roughness from the edges of the oil grooves.
BROACH DETAILS
A reproduction of a standard broach used for bearings, whether babbitted
or of bronze, is detailed in Fig. 155, and in Fig. 156 is illustrated a group of
such broaches. It is to be noted in, the detailed broach that while it is for a
bearing to accommodate a shaft of 1%-in. diameter, the maximum diameter
is o.oOS in. in excess of this dimension, the difference allowing for the running
fit required and for any slight “come back” in the babbitt after broaching.
Experience seems to indicate that there is a tendency for the babbitt to :
expand very gradually after broaching, so that a bearing which has been
allowed to stand for several months will sometimes show a slightly reduced
diameter and this tendency must be allowed for in the broach.
It will be noticed further, that among the group of broaches shown, are
some in which the cutting edge is a continuous spiral, while in others the cut-
I8o BROACHES AND BROACHING
ting is done by a series of circular edges entirely independent of one another.
As far as the actual cutting is concerned, there is no difference between the
two types, but in the matter of keeping the broach free from chips, the spiral
design is to be preferred.
UNSATISFACTORY FORMS FOR BROACHING.
In bearings of the type shown in Fig. 157 whether of cast or malleable
iron or of bronze, the design is such that broaching alone is insufficient to
give a perfect hole, and such bearings while they may be rough-broached,
should in general be finish-bored, if the very best results are to be obtained.
This is on account of the great amount of metal omitted on one side, due to
the large oil hole, which causes the broach when being driven through,
to do little or no cutting on the side opposite. There is, however, a way in
which this tendency may frequently be overcome and that is by filling the
oil hole with babbitt and inclosing the bearing in a suitable pot while broach-
ing, the babbitt being burned out afterward. The broach is thus supported
all around, and is enabled to cut a clean hole and one concentric with the
circumference of the bearing. i .
ExPERIENCE WITH TWO-PIECE BEARINGS
Considerable difficulty was encountered when broaching two-piece
bearings was first undertaken, and various experiments were made without
attaining any pronounced success. The half bearings were milled along
the edges, then fitted together, faced, counterbored and babbitted. The
complete bearing was next set within a forged ring around the circumference
of which, and projecting inwardly, were placed setscrews which could be set
tightly against the bearing, thus Securing it firmly in a central position, the
idea being to have one such ring take in a number of sizes. Upon driving
home the broach, the halves separated slightly, due to an almost impercep-
tible springiness in the Several parts, sufficient however, to prevent any
really satisfactory results. Modifications of this method showed that the
best way to do the work was to surround them with a snugly fitting ring
made for but one kind of bearing, and of size and strength enough to prevent
all distortion. Our procedure now is to rough-broach them in this kind of
a ring, then remove them and clamp them onto a mandrel and finish the
outside, after which they are again placed in another close-fitting ring and
finish-broached. Owing to the fact that the first ring used holds the rough
casting, it is provided with short, heavy setscrews, but the last one used is
bored so that the bearing is a Snug fit. -
PUSH BROACHES FOR A VARIETY OF WORK
The American Machinist published an article by S. E. Summers, mana-
ger of the Detroit shops of the Chicago Pneumatic Tool Co., on the use of
THE DESIGN OF PUSH BROACHES -181
push broaches in the finishing of some of the parts of their air hammers and
other tools, which is reproduced herewith, as it contains much valuable infor-
mation on that class of work.
In presenting this article it is not my intention to convey the idea that
the method shown is the modern way of broaching, but simply to give the
*
- - - - - - -
º - - §
8 # 3 & # 3 & # 3 -
- - c. c. c > → c tº -
-* + + + + + + + + ..!
--- --- -- - - --- --- --- --- --> ---
º º, is is : E → E : *
|
--
*~~ º
ºf--->
º, ižºrad.
- .- 15.--
F---4-------4------------- - 3+% -
FIG. 155-Detail broach for bearing.
-
Fig. 157.-A difficult bearing to broach.
benefit of our experience, and this will serve to show what can be accomplished
on a standard broaching press, which, when not in use for broaching, is busy
on the many assembling operations which can only be handled on a press of
this nature.




I82 BROACHES AND BROACHING
BROACHES FOR HEXAGON HOLES
The halftone, Fig. 158, showing a portion of the press with broaches in
place, will illustrate the method used in broaching the hexagon hole in our
pneumatic-hammer chisel bushing, Fig. 159, the material of which is a high-
grade carbon steel. The length of the piece is 7% in. and the hole measures
*%2 in. across the flats. We use four broaches simultaneously and at each
stroke of the ram we complete one piece. The hole in the blank is bored to
1962 in. and the guide on the broaches is made o.o.o.3 in. under this size. The
follower on the upper end of the broach is made long enough to allow the
broach to drop through the work when the ram is at the end of the stroke.
The broaches, Fig. 16o, are 6 in. long overall and have 14 teeth with 94-in.
pitch. The first six teeth advance o.o.1o in. each or o.oos in. on each side,
as the first few teeth only cut on the corners as in Fig. 161, and no trouble
is experienced, but as the cut becomes heavier it must necessarily be reduced,
depending on the nature of the material and length of the cut. In this
case we find that the teeth can be advanced o.o.o.3 in. with full cut or o.o.o.15 in.
on each side. I know of no rule that can be safely followed for the amount
of cut to allow.
The first tooth on broach No. 2 is made the same size as the last tooth
On No. 1 to assist in centering, and so on with Nos. 3 and 4. The last six
teeth on the finishing broach No. 4 are made parallel to insure the size holding
up to standard.
In the making of the broaches the blanks are turned and milled allowing
a light cut for finishing. They are then carefully annealed, grooved and
the teeth are finished with an end mill to give 2 deg. clearance. There is
practically no hand work required to finish them except to give a little
retouching. If a little care is taken in handling and annealing no trouble
will be experienced in tempering and they will be quite straight. There will
be no trouble from the chips wedging in the grooves if they are properly
formed and a little experience will determine what that is, depending entirely
on the nature of the work, bearing in mind that all broaches must have
plenty of chip room; if not there will be trouble from the teeth breaking.
BROACHES FOR SquaRE HOLES
The broaches, Fig. 162, for the square hole in the piece, Fig. I63, are
made practically the same as for hexagon holes. They are io94 in long
overall, the teeth are of 54.6-in. pitch and the hole when finished is % in.
across the flats. The teeth advance o.o.o.3 in. each or o.oO15 in. On a side.
Three broaches are required for this piece with the work divided as in Fig.
164. In this case we drill the hole in the blank 2%2 in. as we do not require
a perfect Square.
THE DESIGN OF PUSH BROACHES 183
F- -
Fit tº Pluggage
0.5925"Across Flats
after Hardening
Fig. 158.-Broaching press. Fig. 159.-Section through bushing with hex-
agonal hole.
|
Fig. 161.-Sequence of operations in broaching the hexagonal hole.









184
BROACHES AND BROACHING
- - -
wº-º-º-º-º-º-º:
Fig. 163–Piece with square-broa
== 1000000000000000000000，
hes for a square hole.
FIG. I.62.-Broac
me -
FIG. IGA.—Steps in broaching a square hole.
|
ujſjjjjjjjjjjjjjjjjjjjjjjjjjjjjj].
| Uiiiiiiiiiiiiiiii，-
Fig. 165-Another set of broaches,
Tool"Steel
FIG, 166,-Piece broached with the tools
in Fig. 165.







THE DESIGN OF PUSH BROACHES 185
BRoaches for Round Holes witH FLAT SIDEs
From Fig. 165, it will no doubt be seen that trouble was experienced with
the next piece. This is shown also in Fig. 166, and is one of the most difficult
pieces we have ever had to broach. It is of tool steel and is 1% in long,
bored to 3% in diameter, and is broached to 34 in leaving one side flat,
the face being 316 in from center. The same method was used in making
the broaches as for the others, except that they were ground all over after
tempering, by which method we are able to have them perfectly straight.
The three broaches with heavy teeth are practically new and found by
experience to be a better design. The teeth advance ooor in each or o.o.o.o.5
66 Teeth, 20 Pitch
!
--
ſ
- º |
3:670 —-
Fig. 167.-Broaches for internal gears. Fig. 168.-Internal gear to be broached.
in, on each side; they are of 4-in, pitch and the broaches are 8% in long
overall. They also have longitudinal grooves to break the chips which is
quite important in this case.
BROACHES FOR INTERNAL GEARS
The broaches shown in Fig. 167 are extensively used on small internal
gears, of which we have a great many of various sizes, one of which is seen
in Fig. 168. They may look to the reader like very difficult broaches to
make, but are comparatively simple. They are 8% in long overall, with a
1-in. hole running through, cleared in the center allowing 34-in, bearing at
each end.


I86 BROACHES AND BROACHING
After roughing out the blanks they were annealed to remove strains, the
grooves being then cut in the lathe and the teeth milled straight, practically
the same as though making a long gear, as we have found by experience that
no clearance is required. They are then tempered and ground in the groove
to bring the cutting edge up sharp. The cutting is all done on the points
of the teeth and the outside diameters of the teeth advance o.ooč in each,
leaving the last three teeth straight to insure the size being accurate. The
cutting teeth are spaced 36 in. between centers. The gear being broached
has a 93-in. face and 66 teeth of 20 diametral pitch. The blank is roughed
out 32 in. large outside diameter and is held in a collar while being broached
to prevent spreading, after which it is mounted on a special fixture and
centered from the teeth while being finished on the outside to insure the
outside diameter being true with the teeth. This work is all handled in our
Watson-Stillman broaching press, using lard oil as a lubricant.
A BUILT-UP INTERNAL–GEAR BROACH
The following description of a built-up broach, made by a correspondent
of the American Machinist for cutting internal gears, is interesting, though
he admits that two broaches would have given a more satisfactory job, had
the expense not been so great. However, he says, as the job did not re-
quire the greatest accuracy, this being a case of quantity in as short a time
as possible, it was decided to make one broach do.
The broach was made of tool-steel disks, turned to the sizes given in Fig.
169, held together with a crucible-steel binding-bolt not hardened, as we
were afraid it would warp. This was very important as we depended on
the key, which was hardened and ground, to bring the teeth in line. The
disks were turned in the usual manner, allowance being made for grinding
on the flats. The keyway was then put in to gage. The teeth were cut on
a mandrel with a taper shank to fit the dividing head, and a key to fit the
cutter, so the teeth could be located uniformly from the key. These teeth
were cut about 3% deg. taper for clearance. It was only necessary to set
the cutter once for the entire lot of disks, as the bottoms of the teeth were
all alike. After the disks were hardened, they were ground and assembled.
The teeth were not perfectly in line, but were commercially good enough.
These broaches were used in a Watson-Stillman hydraulic press, and our
first trouble was in the tearing of the metal on the bottom side as the teeth
cut through, as the forgings were very tough. This was partially overcome
by leaving a small amount to counterbore afterward, and by using the best
grade of lard oil as a lubricant. The next trouble was in the tendency of
the broach to creep to one side, making the teeth cut out of truth with the
outside of the gear. The remedy for this was to leave enough on the outside
to finish after the gear teeth were broached. From 200 to 225 of these gears
were broached in Io hr. with this tool.
THE DESIGN OF PUSH BROACHES 187
Another writer, commenting on the foregoing, says that he would make
the broach a solid piece of tool steel as shown in Fig. 17o large enough to
turn to the outside of the gear teeth, in this case 3.II6 in., and without any
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calculation beyond a desire for good proportion, Io in. in length. This
should be centered and a shank, I in. long and 2% in. in diameter turned on
one end at a. Then the piece should be strapped to a face-plate, with the




188 BROACHES AND BROACHING
turned end in the steady-rest, and a hole drilled and tapped in the end, with
a T-in. pipe tap, and the edge of the hole trued up for a center. This is used
to Screw in a piece of I-in. pipe to handle the broach with when hardening and
tempering. Next the blank is put between centers and turned for about I
in. at b, next to the shank already turned, for a space about I in. wide and
to the diameter of the gear. The other end c is then turned to the diameter
of the root of the teeth for a little distance. The tailstock is now set over
to turn a taper from c to d. Then while the lathe is adjusted to the taper,
cut a ratchet thread, eight to the inch, the entire length of the taper. After
setting the tailstock back, the 1-in. strip b is threaded, making eight full-
sized threads. It is now ready for the teeth, which are cut parallel, the
cutter just touching at the small end, and going full depth at the other.
The formula º for the full depth of the tooth shows this to be o. Io'78
and as there are 8 in. of taper and eight threads per inch, each tooth will
have a little less than o.o.o.17 in. to cut, which is just a nice chip. When
the teeth are all cut, if the cutter is kept sharp so there are no burrs, the
broach is ready to harden without any kind of hand work being done on it.
A little spring in the hardening makes no difference, as the final sizing
is done by the last eight teeth, which are too short to spring, and as the
bottoms of the teeth are the same size as the hole in the gear blank, it serves
as a guide and prevents creeping.
EXPANDING. HOLLOW CYLINDERS
In the American Machinist A. D. Hallett explains how to expand under-
sized bushings as follows:
In Fig. 171 is shown a button broach that is cheap to make and the life of which
is practically endless when used on metal that has not been hardened. Added
to this, it leaves a mirrorlike finish in the drifted hole when lubricated with a heavy
oil.
I have made a large number of these broaches, using about IIo-point carbon
Steel and allowing nothing for a grind; but after hardening they were polished with
emery cloth. In machining a gradual increase of o.o.o.2 in. to the button was used,
while the ends A and B were left ooo; in. under the diameter of the hole to be ex-
panded. By making these broaches in progressive sizes the limit of expansion of
any metal can be reached and many otherwise spoiled pieces reclaimed.
A PAIR OF PECULIAR BROACHES
In the Jan. I, 1903, issue of the American Machinist, J. L. Lucas wrote:
In Fig. 172 is shown a pair of broaches, used for squaring round holes on Locomo-
bile wheel hubs, that for efficiency and ingenuity go ahead of anything that I have
seen yet. I say ingenuity, for, while all our broaches are made with this style of
tooth, this is the smallest size we use, and it did not leave strength enough to cut the
THE DESIGN OF PUSH BROACHES 189
teeth on all four sides in the regular manner, so the idea of broaching one-half of
the hole at a time is where the ingenuity came in. The first broach is made with
teeth on two sides only, and the other side or back is left round and of the same
|
--------------------6-------------->
FIG. I. I.-Button broach.
diameter as the leading hole through the hub. No. 2 also is cut with teeth on two
sides, and the back is made rectangular, fitting the half of the square that has already
Fig. 172.-A pair of peculiar broaches. FIG. I.T 3.-A diamond-toothed broach.
been broached by No. 1. The result is a nice square hole produced at two strokes,
one stroke of each broach, and the work is done equally well in iron, steel or bronze,
and comes central with the rest of the hub, a very important feature in the work


I90 BROACHES AND BROACHING
they are used upon. This style of tooth is used in all our broaches and never
clogs or tears out the metal, and takes less power than the old-style shearing cut
broach. It was designed and made by the foreman in our tool room, Mr. E. H.
Metcalf.
A DIAMOND-TOOTHED BROACH
A number of years ago the General Electric Co., West Lynn. Mass.,
used the diamond-toothed broach shown in Fig. 173 to broach out round
holes in steel castings. The teeth are backed off slightly and the broach
is used in a mandrel press, about o.o.1 in. of metal being removed with
comparatively little pressure. In order to not leave a line in the work the
spirals are cut with one less flute on the right than on the left.
POWER REQUIRED TO BROACH STEEL
From data obtained from Mr. Spicer, the power required to force
various push broaches through work in a 20-ton hydraulic press, is as follows:
1%-in. leader broach, for 11%.2-in. round hole, 150 to 170 lb. per Sq. in.,
1%, six-spline broach, 90 to IIo lb.; 31.6-in. keyway broach, 5 to 15 lb.; 1%
square broach, 70 to 90 lb.; 1% square broach, finish size, 35 to 45 lb.
The pressure required for 20 tons in this press is about 225 lb., so that
the ton pressure required for the broaches named can be easily calculated.
The high pressure required for the round leader broach is accounted for by
the fact that it cuts entirely around the hole.
CHAPTER VII
MAKING BROACHES
There are numerous ways of making broaches, when it comes to the
actual machining processes. A large factor in the methods used will of
course be the shop equipment at hand. As a general rule it is far better
to have broaches made by firms making a specialty of such work rather
than for inexperienced men to try it. At the present time broaches for
keyways, round, Square and certain classes of multispline holes, may be
purchased almost as readily as are the regular run of drills or reamers, since
the types of broaches referred to are carried in stock ready for quick shipment.
However, Some firms prefer to do their own work, others have to meet
Special conditions which compel them to manufacture their own tools. For
this reason the following descriptions of actual shop practice will be of
interest, and will serve as a general guide for machining, hardening, grinding
and straightening of broaches of various types.
PULL-BROACH WORK
On the shop methods for machining pull broaches, E. A. Suverkrop,
one of the editors of the American Machinist, has been of immense assistance
in gathering the data and the photographs needed to make plain the text.
A large part of the material gathered by him was obtained in the shop of
the J. N. Lapointe Co., New London, Conn., who besides building a line of
belt- and motor-driven broaching machines manufacture an extensive line
of broaches, many of which, for standard work, are kept in stock.
Broaches are made of four kinds of steel: Mild steel, case-hardened;
carbon steel; alloy steel and high-speed steel. Carbon steel is the material
most commonly used for medium and large-size broaches and for fine-finishing
cuts. For small broaches tough alloy steel containing vanadium is used.
High-speed steel is used for finishing broaches in hard material.
The life of a broach is difficult to determine, depending as it does on so
many conditions. A certain carbon steel broach finished 28,000 holes I in.
Square in machinery steel 134 in. thick.
Another broach, made of Colonial Special steel, broached 12,000 auto-
matic pistol frames with two grindings.
TURNING LONG, SLENDER BROACHES
Owing to the small diameter of broaches as compared to their length,
considerable trouble from springing and chattering is likely to be encountered
IQI
192 BROACHES AND BROACHING
while turning the blanks. Follower rests of the usual type are of no use as
the workistapered. A simple self-
adjusting follower rest is shown in
Fig. 174 at A. It consists of a
piece of wood with a notch in it to
fit over the work. Two nails are
driven in the wood, one near each
end. Over these are hung pieces
of iron with holes in them. The
back end of the wood rests on the
back of the carriage. The amount
and location of the weights B is
obtained by trial. Sometimes the
heavier weight is placed on the
lower nail and sometimes on the
upper one. While crude, this
follower rest is entirely satisfac-
f tory and may be of use for turn-
#ing other slender work.
Where broaches are for cylin-
rical work the teeth are turned in
the lathe, making use of the
steady-rest to prevent spring.
# This is a comparatively simple
Flathe job and needs no explanation.
d
-
PLANING BROACH BLANKS
Some broach blanks may be
milled by strapping to a milling
machine table and using standard
cutters. Others are better
handled on a planer. Especially
is this true of angular, interrupted
or formed broaches. For occas-
ional broach planing, special fix-
tures are desirable although not
absolutely necessary, as any good
mechanic will find means to ma–
chine a broach, if he has to.
However, from a commercial
manufacturing standpoint, fix-
tures are certainly needed, and a
row of planers used in the J. N.
Lapointe shop, is shown in Fig.

MAKING BROACHES I93
175. A number of broaches made in this shop are also shown at the ends
of the planing machines. On heavy section broaches, a small table jack is
often sufficient to support the work under the cut, but on small, slender
work, the type of rests shown on the machine in the fore-ground is desirable.
An enlarged view of this last-mentioned machine is shown in Fig. 176. The
headstock A is provided with a spindle and driver which can be rotated by
a worm wheel controlled by the star feed B and the trip C, if the nature of
the work requires it.
Provision is also made for attaching a series of index plates D to the live
head spindle so that broaches can be machined with any number of divisions.
As practically all of the planer work is tapered, the tailstock E is provided
Fig. 175-A group of planers fitted especially for broach work.
with an elevating device. At F is shown a series of planer jacks specially
designed for supporting long slender work. The trip C for clearness is shown
in operating position, although the work G is a square broach and, of course,
does not require to be turned at each stroke of the planer.
The operation of the trip C for such work as requires its use is as follows.
As the end of the work passes the tool on the cutting stroke, one arm of
the star feed B strikes the raised part H of the trip C. In this position,
and with the force applied in this direction, C is rigid and the starwheel is
rotated. When the planer reverses the starwheel B again strikes H but the
force is applied in the opposite direction and C is caused to swing, as the only
resistance is that of the coiled spring I. As soon as the starwheel has passed
13

104
BROACHES AND BROACHING

MAKING BROACHES 195
out of engagement with H, the spring I returns C to the position shown.
When the planer is operating on work such as shown the trip C is swung
and clamped so that it does not engage the starwheel.
MILLING THE TEETH
Fig. 177 shows the cutting of the teethin three keyway broaches at a time
on a Whiton rack cutter. The teeth are in this case cut at right angles to
the axis of the broach, but another holding fixture permits the cutting of the
teeth at an angle. Some care must be exercised when making broaches
with the teeth at an angle. There is always a tendency for the broach to
crowd over to the side when the teeth are cut on an angle, for that reason
the angular direction of the teeth on the opposite sides of a broach should be
Fig. 177.-Milling broach teeth.
such that the tendency to crowd over in one direction on one side will be
counteracted by the direction in which the teeth are sloped on the other
side. This point is plainly brought out in the section on the design of
diagonal-tooth broaches.
Another tooth milling fixture is shown in Fig. 178. This is used in the
shop of the Davis Boring Tool Co., St. Louis, Mo. While this is used in a
regular plain milling machine, a special overarm bracket is employed and
also a special arbor for the milling cutter. The body of the fixture is mounted
on a circular base, on which it may be swung to any desired radial angle.
The hinged bracket is so made as to be easily raised or lowered at one end
so that the work may be placed at the desired slope. In this hinged bracket
is mounted the sliding work holder A, into which the broach blank is

196 BROACHES AND BROACHING
clamped. These work holders are made in various styles to accommodate
the different kinds of broaches made. The work is indexed for the pitch
FIG. I.19.-Milling out the slot in the shank.
of the teeth by means of a pin in the bracket which fits in properly spaced
holes in the work-holder slide. When located, the slide is locked in place
for the cut by means of the clamping lever B.

MAKING BROACHES I97
MILLING THE SLOT IN THE SHANK
The fixture shown in Fig. 179 is very convenient for holding broaches
while milling the slot in the shank. It is also useful for other work of a
similar nature. No detailed description is needed, as the engraving plainly
shows the construction. *
ANGULAR TAPER BROACH MILLING
The following directions for angular taper broach milling were worked
out by D. M. Lidell, who writes:
The general procedure in angular taper broach making resolves itself into two
operations, turning a frustum of a right circular cone, and then milling it into the
frustum of a regular pyramid. It is proposed to give here some simple formulas
by which the depth of cut in the milling operation necessary to produce any pyra-
mid from 3 to 15 sides can be readily calculated, provided the diameters of the
ends of the frustum of the cone be known.
These calculations are to be made by means of Table XXXI, in which d signifies
the diameter of the circular end of the frustum. “Mill off d” signifies the propor-
tion of the total diameter to be taken off in making each face. The table is used as
follows: If it is desired to mill a six-sided broach from a frustum of a cone, the end

TABLE XXXI.-CONSTANTS FOR BROACH MILLING
Sides in finished broach Mill off d Leave d
3 O. 25OOOO O. 750ooo
4. o. 146446 o. 853554
5 O. O954QI O. 904509
6 o. oG6987 O. 933OI3
7 O. O495I 3 o. 95.0487
8 o, og8o0o o. 96194o
9 O. O3OI 54 o. 96.9846
IO O. O.244.72 O. 975.528
II O. O2O255 O. 979745
I 2 O. OI7O37 o. 98.2963
I3 O. OI4529 o. 98547I
I4. O. OI253O o. 987470
I5 o, orog 26 o. 989.074
diameters of which are I}6 in. (I.1.25 in.) and 5% in. (o.625 in.) respectively, the cut
at the large end should be o.oč6987 × 1.125 in. = o.o.75360 in. deep, and at the
small end should be o.oë6987 X o.625 in. = o.o.41867 in. deep. The factor o.o.66987
is taken from the table, opposite 6, the number of sides desired, and the second
terms are the end diameters d, as left after the cut.
In the particular case under discussion, to make the cut, the tailstock should
be elevated by an amount (I.125 — o.625) (% – o.offé987) = o.5 X o.433013 =
o,2165065 in. If, with this elevation, a cut o.o.419 in. deep be taken at the Small
198 13POACHES AND BROACHING
end, it will be o.of 54 in. deep at the large end. Or, in the general case, if we repre-
Sent the two diameters by a and b, and the constant taken from the table for any
given number of sides as k, the formula for the elevation of the tailstock will be
(a – b) (3% — k).
For instance, if a 15-sided broach were to be cut from a frustum of a cone with
diameters 1946 in. and 716 in., elevate the tailstock (1846 – 746) (% – o.o.10926)
= (o.75 X o.4890.74) = o.366805 in., and then take a cut 716 X o.oroQ26 =
o.oo478o in. deep at the small end; rotate the dividing head 360 deg. + 15 = 24
deg., and mill again. -
It may be noted that while these constants, working on perfect machines,
would give perfect results, in practice one must make allowances for the imperfect-
tions of the dividing head and machine. For instance, it can readily be seen that
if a triangular broach is to be milled and the work rotated 120 deg. by the dividing
head, and it proves to be only II9 deg., the theoretical cuts will slightly overlap,
and the broach will be small. Consequently, after giving the tailstock the theoret-
ical elevation, as nearly as possible, take a cut a little scant (a few ten-thousandths)
of the theoretical cut. This will give a small land at the corners, but the radius
will be the full theoretical amount.
If anyone is interested in calculating out the above figures, or those of any
other number of sides, for himself, the formula is (for a pyramidal frustum of n
sides): Mill off *(* ( – COS 360 ))
2%
MAKING PUSH BROACHES FOR STEEL WORK
The shop practice of the Spicer Manufacturing Co., Plainfield, N. J.,
in making push broaches, is the result of several years of experimenting in
an effort to find the proper proportions, machining methods, steel and
hardening processes for broaches that would give satisfactory results in
working out holes of various sizes and lengths in tough, 40-point steel forgings
from which its universal joints are made.
Besides having the teeth of proper size and pitch, with plenty of chip
clearance, ease of machining should be considered in designing a broach,
especially if many of them are used. If the machining is difficult, the cost of
keeping a large number of sets to size soon becomes burdensome to the most
prosperous shop.
The objection frequently heard regarding push broaches is that they have
a tendency to twist or creep in the work, but if properly made this trouble
will not be encountered, and no subpress or other guides will be necessary.
MACHINING BROACHES
In machining broaches like those shown in Fig. 180, which are for a
square hole with round corners, according to the standard of the Society
of Automotive Engineers, the practice at the Spicer shop is to Center and
turn the blank according to the dimensions given in the Specification for
MAKING BROACHES I99
a certain size hole. Specifications of the kind referred to were given in a
previous article for a large range of push broaches.
After the blank has been turned, the teeth are cut the proper pitch and
diameter. It will be seen that this is an ordinary lathe job, the blanks for
4.
Fig. 180.-A set of broaches for a round-cornered square hole.
all common sizes being short enough and stiff enough, the length ranging
from 5 to 12 in., according to diameter, to be turned to the given dimensions
without trouble of any kind.
Fig. 181.-A set of broaches for a ten-spline hole.
The next step is to place the blanks between the centers of a miller, using
a dividing head for indexing purposes. The flats of each broach are milled



2OO BROACHES AND BROACHING
parallel with the center line and all the same distance from this line. This
differs from the more common practice, in milling square broach teeth, which
is to step up each one separately. The advantage and saving of time by
the former method is obvious.
From this it will be seen that the matter of tooth increase sizes for this
class of broaches is entirely one of circular turning or grinding, an operation
easily gaged by micrometers. This is not the case where the flats are stepped
up, as often the blank must be indexed several times to get the desired dis-
tance between parallel flats.
The round or pilot ends of a set of broaches of the type shown are all
made the same diameter, and the first “teeth” do not cut but merely act
as guides in the grooves cut by the preceding broach. The large end is
turned cone-shaped, to fit the push pin used in the press ram to force the
broach down through the hole. This automatically centers the broach, and
the pilot and pilot teeth effectually guide it.
These, together with the accurate method of grinding the cutting teeth,
prevent all tendency to twist or creep in the work. Of course, the work
is accurately centered under the broach by means of a locating ring or
bushing. It is also the practice to accurately size the hole to be broached,
by means of a sizing or “leader” broach, so that the pilots will fit, and not
bind or wobble.
MULTIPLE-SPLINE BROACHES
The multiple-spline broaches are turned in practically the same way as
the Square ones, but the milling is, of course, different. The bottom of the
flutes of each broach are milled parallel with the center line all the way, and,
in order to break up the chips, every other tooth of a line is grooved, as
shown in the ten-spline set in Fig. 181. This takes less power and produces
a smoother cut, there being less tendency to tear the metal.
The pilot teeth in these broaches are beveled on each side of the entering
end, to facilitate insertion, and guide the broach without a tendency to
“Scrape a twist” one way or the other. An enlarged view of some of the
Cutting teeth of ten-spline broaches is given in Fig. 182.
Samples of the holes cut by the square and six-spline broaches are shown
in the parts of the universal joints, Fig. 183. Very accurate work is done on
these parts and in Some cases as high as 23 push broaches are used in a set.
Great care is taken in grinding the teeth, after hardening, to produce
just the right amount of undercut and radius at the base of the teeth to
produce a nice curling chip. The chips shown in Fig. 184 are evidence of
the success of this work.
HARDENING BROACHES
Since the hardening of as important a tool as a broach is usually done
by a skilled hardener who knows his steel and how to handle it, detailed
MAKING BROACHES
2OI
Fig. 184.-Chips, showing curl given by properly shaped tooth.

2O2 BROACHES AND BROACHING
directions are superfluous, but it will not be amiss to outline in a general
way how some firms handle their work. As previously stated, broaches are
made of four kinds of steel: Mild steel, case-hardened, carbon steel, alloy
Steel and high-speed steel, the last named being of the tungsten class. Of
the alloy steels, carbon-vanadium seems to give very good satisfaction for
broaches. This steel is simply a high-grade carbon steel containing vana-
dium, but no tungsten or chromium. The addition of vanadium gives the
Steel a greater heating range without coarsening the grain. This steel is
recommended to be hardened at from 1350° to 1425°F. The temperature is
then usually drawn to about 460°F. Where carbon steel is used for broaches
the carbon content should range around 1.0 to I.Io points. To prevent
excessive warping, it is a good plan to rough out a broach and then anneal
it before proceeding farther. Open-hearth steel of about o.25 points carbon
content makes a very good grade where case-hardening is resorted to. The
general procedure is to pack these broaches in a tube or box with ground
bone, and heat to about I700°F. The box is then allowed to cool slowly
without disturbing the contents. It is then again reheated to about 1475°
and quenched. The temper is then drawn to about 370° or 38oº F., or in
Some cases 15° or 20° less than this.
When a broach has become warped in the hardening process, it may be
straightened between wooden blocks with a mandrel press, or other similar
means. Better results are usually obtained if the straightening is done at
the time the temper is drawn. The warped place may be heated with a
gas torch or any other means that can be easily controlled, care being taken
not to heat the spot hot enough to draw the temper, which is sure to happen
if the drawing temperature is exceeded. In handling any unfamiliar steel,
it is the better plan to closely follow the maker's directions as to the tem-
peratures allowable, as they can generally be relied upon to give the user
the benefit of their much wider experience.
The method of hardening used in the Alco shop is as follows:
The steel used in making the Alco broaches is known as Styrian Blue
Label, and the broaches are packed in large tubes with a screw cap on each
end. The packing material consists of charcoal 2 parts and leather I part,
and there should be at least 1% in. of the mixture on each side.
The tubes are put into a Brown & Sharpe coal furnace at about Ioooº F.
and heated to 1500°, the time depending on the size of broach being heated.
For a 1-in. broach the time taken to heat properly and allow the carbon to
“soak in.” is 2 hr. For a 194-in. broach, 2% hr., and a 1%-in. broach,
3 hr., or an average of an additional half hour for every quarter-inch increase
in size.
When properly heated, the broaches are quenched in a large deep tank
filled with thin linseed oil, being held by the shank and plunged vertically.
This leaves the teeth extremely hard and tough and the inside comparatively
soft. The broaches are next drawn in oil to a light straw color, or to a
MAKING BROACHES 2O3
temperature of between 400° and 450°F. Any necessary straightening is
now done in a straightening press, careful heating being done with a torch,
but this is seldom needed with this steel and method of hardening.
Two or 3 years ago, I wrote regarding push-broach practice that the
Selection of the proper steel and the method of hardening have been the ruin
of many a would-be broach maker. Many have tried the most expensive
steels obtainable, only to find, after carefully machining the difficult stuff,
that it was wholly unsuited for the purpose.
After running the entire gamut of the steel scale, the Spicer Manufactur-
ing Co. has settled on an open-hearth steel of from 20- to 25-point carbon
Content. Broaches made from this steel are easily machined, give no trouble
in hardening or tempering, and have a life of from 2000 to Io,000 pieces each,
before reaching the scrapping limit of o.o.o.2-in. undersize.
The hardening process is the ordinary one of case-hardening, the broaches
being packed in tubes, with slightly charred ground bone, and heated to
about 17oo°F. for from 4 to 8 hr., depending on the size of the tools being
hardened. -
The quenching is first done in water, the broaches being plunged straight
down into the tank, and held under until the teeth turn black, then finish
cooled in oil. The drawing, or tempering, is done in an oil bath heated
to 350°F., which, it will be noted, is considerably less than for tool-steel
tempering.
GRINDING BROACHES
The grinding methods for all sorts of shapes are now so familiar to every
shop man that it is useless to go into details here. With the outlines given
in the chapter on design, any ordinary grinder should be able to finish a
broach on his grinding machine without much instruction. Round broaches
are of Course the easiest to grind, then next is the common keyway broach
of the sliding-blade type. Following this is the square broach and thence
on to the more difficult forms.
A simple method of grinding keyway cutter bars is shown in Fig. 185.
The grinder is fitted with a magnetic chuck and the cutters are ground all
over. The bars may be removed at any time for measuring and instantly
replaced without any trouble whatever. By tilting the chuck the back of
the broach may be ground to any taper desired.
We have a great many keyway broaches to sharpen, says M. V. D. in
the American Machinist, and so we have made the grinding fixture shown
in Fig. 186. -
The cutters are about 18 in. long and have been found by trial to work
best when given a taper of about 962 in. in that distance. The fixture
consists of a flat piece of cast iron, planed all over and bolted on the table
of the cutter grinder so that it is flush with the edge of the table nearest the
wheel. This piece is shown at A. The table is swiveled to get the angle X,
204 BROACHES AND BROACHING
which is the clearance desired on the teeth. Bolted to A is a bracket B,
which carries the lever E, and also acts as a cap or guide for a small angle-
shaped gage C, which freely slides in and under it.
One end of E is made eccentric, so that when thrown back it locks the
gage piece C against D; the other end carries a gage F, which engages with
the teeth of the cutter to be ground. D is a taper piece slightly longer than

MAKING BROACHES 2O5
the cutter, with one end bent so that the end of the cutter carries it along
when moved to grind the next tooth. This end of D is 9%2 in. thinner than
the other, or just the clearance desired on the cutter.
To operate, place the pin G in the hole, as shown, bring the front of the
tooth I against the gage F, which also places cutting edge in line with the
point of the gage C, against which it must be drawn; next slide D along
until the end touches the cutter, then pull the lever E back, thereby locking
C and D against A.
We now have three solid points, G, C and D, to locate the cutter. The
tooth I is fed past the face of the cup wheel by moving the table of the grinder.
To grind, the next tooth E is again swung forward, releasing D, and the
cutter is moved to bring the next tooth against F; it carries D along with it
where it is locked, and the tooth is ground in a similar manner to that pre-
viously described.
r-
—H-
+–r
|-
|-
--
~!
i
g-
| | || || || || || || 5 || || || fiftºfºilſ
–– #H#
y § jë | ſt A |
—l : -:
FIG. I86.—Fixture for grinding keyway cutters.
As the taper piece D is fed along, it gradually gets thicker, thereby
causing the gage C to be slightly receded for each succeeding tooth. When
the cutter has been about half ground, pin G is taken out and put in the hole
H, which is placed about ¥64 in. back of the line of the other hole and the
gage piece C; this is to allow for the taper, but does not need to be accurate,
as the grinding is done directly in front of the gage C, and any variation in
the location of H would only mean a difference in clearance and not in taper.
A method of grinding relief on broach teeth, used in the J. N. Lapointe
shop, is shown in Fig. 187. The work A is a finishing broach ground to
size in a previous operation. Indexing is accomplished by means of the
finger B and the work is fed past the wheel.
In speaking of work done on square and spline broaches, a writer in the
American Machinist says:
The grinding is done between index centers on a regular grinder, using
a free cutting wheel. The six-spline broaches are ground by using a thin
wheel, set over the center line and grinding lengthwise of the flutes, rotating

206
BROACHES AND BROACHING
'qqaaq aqq ſºuſ-Aaſia（I—， 181 '51） I

MAKING BROACHES 2 o'7
the broach the necessary amount to grind the radial bottom and sides of
the flute.
The lands of the teeth are ground perfectly parallel with the center line
of the broach, and in case any relief seems needed in practice, it is given by
hand by means of a small, hard oilstone. Just back of the land, which is
usually 9%.2 in., there is a relief of about 2% deg. given.
}
TESTING DEPTH OF CUT PER TOOTH
After a broach has been ground, it is a good plan to try it out to see that
none of the teeth have a tendency to “hog in.” or cut more than their due
share, for if they do it is liable to result in clogging with chips, springing or
even breaking of the broach, to say nothing of ruining the work. Several
things may be the cause of unevenly cutting teeth, either warping from the
hardening process, which has not been eliminated or else from the release
of unexpected strains during the grinding, or secondly, from uneven grinding
of the teeth, which may be the operator's fault or possibly a result of the
warping mentioned. In any case the broach should be tested out before
being put into actual service on any valuable work. To do this testing,
first use a piece with the required size and shape of hole in it, but not longer
than twice the pitch of the teeth. The broach should be run slowly through
this and the amount of chips made by each tooth carefully noted. The
high teeth can then be stoned down, and the broach again run through a
slightly longer piece, finally running it through the full length of hole it is to
broach in actual use. In this test, not only should the amount of chips be
noted, but also whether they have the proper curl for the material on which
they are working. If any radical faults are seen, they should be corrected
and note made of them to be avoided in future broach making.
APPENDIX
Recommended S.A.E. practice for the dimensions of square broached
fittings, 6-spline fittings, Io-spline fittings, 4-spline fittings and taper
fittings with castle nuts.
I4. 2O9
BROACHES AND BROACHING
TABLE XXXII
SGRUARE FITTING's
---|--
| sº
|*||
- H
FERNMANENT FIT
Ds. | Dw
sl_\ F. FIT
de l clh Ds | Dh

APPENDIX
TABLE XXXIII
(2 SFLINE FITTINGS
FERN1ANENT FIT
º
*
y
%
To slic E when Nor
UNDER LOAD
TO SELi DE \/VHEN UNDER
L.OAD
#7:iſºzializia; 15°
vv = .25 D w = .25 D
Yn. = .O 75 D Th. = ..! O D
d =.35 D' cl =.8O D
D | cºl w T D | a |w T
A5CI.G.38|_.188 .750 . (2 OO ..!
###|##|-i: , 17 .74d #####| | 52
.875 .244.2 la .375.70 ol.2T a 2O7
.874|.óða .2
1.OOO}_-85O1.25O
āāālīzā|:ā 208
22
º
2
7O
|I. I 24- 355 .283O
II 2Eſ...a52.25i 223
I.OOOH.8 OO .25
aad, .7cłaj .242
!. 1 25|_º|OO .281
ižília:#| #55 342.
1.25O1.C 23].313
ižićzīāīā| 325
1.25O 1. OOO .3 || 3
#######|:##|42.
1.375: I. I Gºd|2344
ižijižājāzīā|3°3
1.375 m. OO .34
1.3Z4. #23 ###| 510
1,447& 1.274 .
| 1.5CO 1.2OO .37
iziââ|jazīlīāzī (203
I.SCO 1.275] .375
####### 465
1.2251.33,
*O6
ºiliº ºf 550
1.75O|1.575 :
1.74all.574 A.37
####|422
4
4.
1.750 ſ.488 4-3
1.74& É # 237
1,755TAOOTZ;
1.225 I.3OO 4-02
!...@24|1.2&nd # 713
ižālīāāālizīā’; B27
Taağı Vaiś Zła
2.25O2O2.5].5C23
£99.9999-392 s.70
2OOOH 1.7OO ..SOO
jazīāīāāizºá. 833
##|1313|#2 *liosa
DOO ||.2OO .500
i.aaS 1.5~8 ###|| 080
.25O 1.8OO |. 523 13@7
2:#########: 721 2.248. 1.<! 2.5@ 2.2481.7633 .52 |
_l. 2.500[2.25O|..Q.25 2,500.2.125|.Q,25 2,500|2.Oool.625
###3 ######| Bºll ###########|300 ########|1688
3.OOO!2.7CO .750 3OOOI2.550, 75 .OOO!24OO TV EO
* :##########|283 # Žišā-āś1873 âââjîă2439
TT = IOOO X (2 X N1EAN FR X. Th. , X \ =
|NCH - POUND's TORQUE CAPACITY PER INCH
BEARING LENGTH AT IOOO LBS. FREssurE PER squaw RE INcri or sucts of splitles.
No ALulowANot E is r-1Abe Fofº RAct 1 or corrueFs NoF Fort clear Atuces.





BROACHES AND BROACHING
TABLE XXXIV,
iO SPLINE FITTINGS
FERN1ANENT FIT TO suildE VVHEN NOT TO SLIDE WHEN UNDER
UNDER - OAD - U-OAD
VV = .1562 D | VV = .1502 D w = ..] EQ2 D
Th. = .045 D Th. =.O7 D h = Ocºl E. D.
d = <! I D cºl = 52 D c. *=8 | D
D cl VV | T
e .750.2 7
– †:#|ā7|iić| 24!
e .875 ºz Oa|_i 3.7
ſºmmemº e g ###5Elijää 324
I.OOO_3,\ 0 |_. & º º 1.OOO! .8] O] .15 a 30
.dad a Oaj .155 aad # º al e - E5
L|l.l 25||.024.1 /2 I. 25 ºló8.1 7Q l, l 251 & 1 || || 72
'# |O2. #########| 412 iāzīāīāji=##| 545
I+|###9||:#2. ##91.975|| 1:15 soa 350l.913|-135 & 72
4- # . 137 24a ||.O74 .1 ºz. .242 # #
3|1.375:1.251 375 i. 1833. .2. IE 1.375 l. l I4: .
| #######|. ######| #: @14 #####|###| 813
_1 ||.5OO!!.325|. JEOO! I.2°10] .234 -, -, 500||1.215.
la i. : - TZ32 #########| *@7
º + & ! (2|.
e * |5|.
T= 1000 × 10 X MEAN R X h X l = INcH-Founds roRque cAPAct-ry FER inch
BEARING LENGTH AT tooo Les. PREssure PER square inch on supes of
sRLINEs. No ALLowANcE is tº Ace Fort RApii on CORNERS NOR FOR Cl-EARANCEs.









APPENDIX
2I3
TABLE XXXV
4- SFLINE FITTINGS
FERN1ANENT FIT To su IDE when Nor
UNDER LOAD
BEARING LENGTH AT tooo Les. FREssuſ’E PER square. INch on sides of sRLINEs.
4- - A
vv = .22+ 1 D
Th. = , OTZE D
cl = .35C D
NOfth-
§ D a w h. | T D | a w h. | T
3 | .750|_. Half- e * • I & Ll : E= }
# 3:3 £3% #H#| 7s %à #|###|###| 23
~2
# |###|-###|##|### 1 oz| |3%;|2.ÉÉ|3}}|...}33| 27
iáāāſāāſāāīā: ############
| |*######|###|###| 1== #| ###|###|###| ***
'# HäHä|:##### 175 Hälſälä|:#| 277
>
14|######|###|###| enz| |######|###|:É| 34
13|#####|###|###| 22e |#######|###|###| 44
| | |. .27 El .3 2 - . 25 | .
! #|########|#####| = | #33}##|###|###| 4a
AE. I.Q2.5||1.33 iſ .3°l li. 1 22 I,225, 1.2.1 °ll .3°1 Ll -2O3
ºliº:#####|###|:###| 337 :liáiã|:#5|###| 577
ilāHää, äl:###| 424 #3|####|###|###| 270
2COCl. 1.7CO] ºz| < 1 EQ 2.OOO! .5CO] .432] .25C
########| * #######| *75
º: Tiā. gº 2->
2#######|###|##| Zoe ######|##3 ##| loo
ſ > •->
2#######|#33-#4 ecs |######|###|:##|=25
OOO)2.55G) . 72.3| .2.25 3.0CO2.2ECT:723ſ.375
3 ########|###|###| 24° ########|-43 fº1=1<!
T= IOOO X 4 X MEAN FR X h. X l = |Non-Pounes roRque capaciºre PER inch
No Al-LovaNCE is MADE Fofº RAD11 on coPRNERs NoF Fort cl_EARANces.

2I4
BROACHES AND BROACHING
TABLE XXXVI
TAFER FITTINGS
PARALLEL ro
Ls
%
KZaº
%
\\
TAFER 13 N 12.
Ls|Lkill_t |Dt E Tru.

















APPENDIX 2I 5
RECOMMENDED STANDARD DIMENSIONS OF KEYS AND KEYSEATS
By Baker Brothers, Toledo, Ohio
The subject of adopting dimensions of keys and keyseats is one that is
now attracting considerable attention among progressive manufacturers.
The annoyance of fitting keys to work of various widths, depths and tapers,
can hardly be estimated, and unless some standard uniformity of sizes is
adopted, duplicate work cannot be produced. We have standard sizes for
taps, drills, wire and gear teeth, and standard tapers for twist-drill shanks.
Why not for keys and keyseats? The subject is one to which our attention
has frequently been called, and realizing the need for something of the kind
we have, after careful study and experience, prepared the following rules,
together with Fig. 188 and Table XXXVII.
GENERAL RULE
The width of the key should equal one-fourth diameter of shaft.
The thickness of the key should equal one-sixth diameter of shaft.
3-inch Shaſt \
FIG. I.88.-Recommended proportions of keys and keyways.
The depth in hub for a straight keyseat should be one-half thickness of
key.
The depth in hub at large end, for a taper keyseat, should be three-fifths
thickness of key.
Standard taper for all keyseats should be 31.6-in. in I ft. of length.
The depth to be cut in hub for taper keyseats, at large end, is greater than
those cut straight, for the reason that unless this was done the depth in hub
at small end would not be sufficient, especially in long keyseats.
The depths of keyseats in table are given in thousandths of an inch, corre-
sponding to the graduations on the index of our micrometer depth gage, and
is measured from the edge of keyseat, and not from the center. In this
manner the exact depth of keyseat can be measured at any time after it is cut.
For extra long keyseats the depth cut in hub might be slightly increased,
but for the average run of work the table will be found correct.
Manufacturers who adopt this rule will always find their keyseats of
correct proportion, and will have no difficulty in duplicating their work,
thus saving themselves much care and annoyance.

2I6 BROACHES AND BROACHING
TABLE XXXVII.-RECOMMENDED DIMENSIONS OF KEYS AND KEYSEATS

Preferred | Nearest | Preferred Nearest P:* ; Depth at
* | *|† : ººlºº
ey
I I. O. 25 % o. I66 %6 O. O93 O. II 2
I}í6 I oô2 o. 265 % o. 177° %6 O. O.93 O. II 2
I}% I. I.25 o. 281 % o. 187 316 O. O93 O. II 2
1316 I. 187 o. 296 94.6 o. IQ8 %2 O. Io9 O. I31
I}4 I. 25 o. 312 94.6 o. 208 %2 O. Io9 O. I31
1916 I. 3 I 2 o. 328 946 O. 2 IQ %2 O. Io9 O. I31
I3% I. 375 O. 343 % o. 229 % O. I 25 O. I5
1%. 6 I. 437 || O. 359 % O. 239 % O. I 25 | O. I5
I}% I. 5 O. 375 % O. 25 % O. I 25 O. I 5
1946 I. 562 O. 39 % o. 26 % O. I 25 O. I5
I5% I. 625 o. 406 %6 o. 27.I %2 O. I4 I o. I68
11}{6 I. 687 O. 42 I %. 6 o. 281 %2 O. I4I o. I68
134 I. 75 O. 437 % 6 O. 292 %2 O. I4. I o. I68
Il 346 I. 812 O. 453 %6 O. 3O2 %2 O. I4I o. I68
1% I. 875 o. 468 % O. 3 I2 1.%2 o. I 7I o. 206
11546 I. 937 o. 484 % O. 323 1.%2 O. I 7I o. 206
2 2. O. 5 % O. 333 1.%2 o. I7I o. 206
2}{6 2. oG2 O. 5I 5 % O. 344 1.%2 O. I 7I o. 206
2% 2. I25 O. 53 I % O. 354 1.%2 o. I 7I o. 206
2% 6 2. I87 o. 547 % o. 364 1%2 o. I 71 o. 206
2% 2. 25 o. 563 % O. 375 1.%2 o. I 7I o. 206
2916 2. 312 o. 578 % o. 385 1.%2 O. I 7I o. 206
2% 2.375 O. 593 % o. 396 %6 o. 218 o. 262
2% 6 2.437 o. 609 % o. 4O6 %6 o. 218 o. 262
2% 2.5 o. 625 % o. 4I6 %6 o. 218 o. 262
2% 6 2. 562 o. 64I % O. 427 %6 o. 218 O. 292
2% 2. 625 o. 656 % O. 437 %6 o. 218 o. 262
21}{6 2.687 o. 672 % o. 448 %6 o. 218 o. 262
2% 2.75 o. 687 % o. 458 %. 6 o. 218 o. 262
21%. 6 2.812 O. 703 % o. 469 %6 o. 218 o. 262
2% 2.875 O. 7I9 34 O. 479 % O. 25 O. 3
21%. 6 2.937 O. 734 % O. 49 % O. 25 O. 3
3 3. O. 75 % O. 5 % O. 25 O. 3
3% 3. I 25 o. 78.I 34 O. 52 I % O. 25 O. 3
3% 6 3. I87 o. 797 34 O. 53I % O. 25 O. 3
3% 3.25 o. 812 34 O. 542 % O. 25 O. 3
3% 3.375 o. 844 % O. 562 % O. 3 I 2 | O. 375
3%6 3.437 o. 859 % O. 573 % O. 3 I 2 | O. 375
3% 3.5 o. 875 % o. 583 % O. 3I2 O. 375
3% 3. 625 O. 906 % o. 604 % O. 3 I 2 O. 375
31}{6 3.687 O. 923 % o. 614 % O. 3I 2 O. 375
3% 3. 75 O. 937 % O. 525 % O. 3 I2 O. 375
3% 3.875 o. 969 T o. 646 1}{6 O. 343 O. 4I2
31%. 6 3. 937 o. 984 I o. 656 | 1946 O. 343 || O. 4I 2
4 4.4 I. I o. 666 1}{6 O. 343 O. 4I 2
INDEX
A
Adjustable broach, *96, *I49, *150
Advantage of broaching, 2
Allowable tooth load, II 5
Auel, C. B., 178
Angle of clearance on teeth, IIo
of tooth face, IIo
Angular taper broach milling, 197
Atlas Press Co., 23, *25
Automobile wheel hubs, broaching, *35, 36
B
Babbitt bearings, broaches for, *178
Bad teeth, grinding, I43, 144
Bagley & Sewall Co., 45
Baker Bros. key and keyseat dimensions,
215, 216
Bath spline grinder, 124
Bearing broach, 36, *38
holder to prevent spreading, *37
Bearings, broaching flats on, 57, *58
broaching and burnishing, 36, *37
Billings & Spencer broaching press, 78, *8o
Billings & Spencer Co., 77, 99
Broach as a clamping medium, 2
making, IQI
support, *g, *Io, *I 2, *35, *41, *44, II 7
with detachable end, *r 18
Broached work, Brown & Sharpe, 126, *127
examples of, *3, *4
what it is, 1, 2
Broaches for babbitt bearings, *178
for internal work, 5, *6, *7
for round-cornered square holes, *I 27,
*I 28
number to use, IIo
original uses of, 2
pull type, 5, *6, *7
push type, 5, *7
types of, 5
Broaching, advantage of, 2
and reaming cost compared, 87
definition of, 1, 2
Broaching, keyways, 26, *27
machine, double end, 48, *49
largest, 54, *55
made from a lathe, *28,
*29
pull type, 8, *9, *Io,
*14, *15
push type, 16, *17, *18, *19, 20, *21,
*22, 23, *24, *25
machines, improvements in, 2
outside of hub core, 57, *6o
several pieces at once, *53
square holes, 2
tools, uses of, 2
Bronze, broaches for, 178, 179, 180, *181
broaching, 39
Brown and Sharpe, 40
broaching practice, I26
Built-up internal gear broach, 186, *187
Bullard Machine Tool Co., 47
Burr, John T. & Son, 15
machine, *15
Burrs, removing with broach, *118, II9
Burton Machine Co., 30
Button broach for expanding hollow cylin-
ders, 188, *189
broaches, 129, 134, *135, 188, *189
:k :k
II, "I2, I3,
C
Cam holding fixture, I55, *I56
internal, work on, 48, *5o
Cams, sub-press for, 81, *82
Campbell, Paul, 85
Capacity of machines, 8, 13, 15, 16, 19, 20,
22, 23, 24
of a single broach, IIo
Chambersburg Engineering Co., 69
hydro-pneumatic press, 69, *70
Charts for broach design, Io/, *Io8, *Io9
Chase, broaching out corners, 51, ’52
Chatter, to eliminate, 5
Chicago Pneumatic Tool Co., 81, 18O
Chrome—nickel steel, oil for, 39
Cincinnati Shaper Co., 99
2I?
2 I 8
INDEX
Clearance angle of teeth, IIo
for sliding gear splines, 134, *135
Colt pistol stock, broaching, *149, *15o
Colvin, Fred. H., 48, 85
Connecting rod ends, broaching, *37, *38,
*41, 68, *70, *71, *72
work, *38, 39
Continental Motor Co., 68
Cored hole, broaching from, II 7
Cost of square broaches, 121
Cotter, holder and broach, *42, 43
Couplings or holders, 150, *151, *152, *153
Crank press, broaching with, 66, *69
Cutting compound, 39
eight oil grooves at once, 93, *95
to a shoulder, I
D
Davis Boring Tool Co., 59, 145
Dayton Electrical Mfg. Co., 88
Definition of broaching, I, 2
Depth of cut per tooth, Io8
testing, 207
Design of broaches, charts for, Io'7, *Io8,
*Io9
of keyway broaches, III
of pull broaches, Ioč
of push broaches, 157
of round broaches, II6
of Spline broaches, 134
of Square broaches, II9, 120
Detachable end broach, *118
Detrick & Harvey Machine Co., Ioa.
Diagonal tooth broaches, 5, 145, *147
Diamond toothed broach, *189, 190
Differential pitch, Ioë, III, *147, 148
tooth pitch, 5
Dimensions of hexagon pull broaches, 129,
*13o, *132
of push broaches, tables for, 157 to 178
Double-end broaching machine, 48, *49
keyway broaches, table for, 115
keyways, cutting, I 13, *114
Spindle machine, *Io, 12, 13
Drifting, I
D-shaped holes, broaches for, *184, 185
D-washer broaching, *g.8, 99
E
Economy of broaching, 5
End of a spline broach, *140, I4I
Ermold, E. A., 87
Error due to undercutting teeth, *125
Examples of broached work, *3, *4
of pull broaching work, 26, *64
Expanding hollow cylinders, 188, *189
rings, finishing ends, *46
External broaching, 57, *58, *59, *60, *84,
85, *86
F
Face angle of teeth, IIo
Fiat Motor Co., 91
Fixtures for planing broach blanks, I 92,
*193, *194
Flats on bearings, broaching, 57, *58
Follow broaches for wrench work, 78, *79
Ford Motor Co., 85
Formula for tooth pitch, Ioč
Four broaches in machine, 4o, *41
G
Gear broach, internal, *I 2, 13
broaching internal, 51, *52
holders, 154, *I55, *I 56
Gears, motorcycle, broaches for, 145, *146
splining, *47
General Electric Co., 190
Generator spiders, small, 88, *90
Greene, T. B., 43
Grinding allowance for teeth, 158
bad teeth, I43, I44
broaches, 203, *204, *205, *2O6
spline broaches, *136, 139, I42
square broach teeth, *I 23, 124, *I 25
Groocock, Walter G., III, I43
Guides for broach, *9, *Io, *I 2
Gun recoil valves, broaching, Io.3, *IoA
H
Haberer & Co., 154
Hallett, A. D., 188
Hand broaching press, Pletz, 92, *93
machine, horizontal, *96
-operated press, 23, 24, *25
Hardening broaches, 200, 202, 203
Haynes, R. C., Ioé
Helical grooves, cutting, 5
Henry, M., 33
Hexagon hole in gear blank, *74
holes, broaches for, 182, *183
Hey, George, I 78
INDEX
2I9
Holder, bearing, *37
or broach coupling, *II 2, 113
Holders or couplings, 150, *151, *152, *153
Holding inserted blades, *II 2, 114
Horizontal hand machine, *96
machines, 8, *9, *Io, *II,
I3, *14, *15, 16
Hubs, automobile, broaching, *35, 36
Hydraulic-operated machines, 16, * 17, *18,
*19, 20, *21, *22, 23
Press Mfg. Co., *18, *19, 20
Hydro-pneumatic press, 69, *70
:k
I 2,
I
Inserted tooth broaches, I I I, *I 12,
I48, *149
Sections, *45
Internal cam work, 48, *5o
gear broaching, 51, *52
gears, broaches for, *185, 186, *187,
I88
International Harvester Co., 61
Irregular pieces, broaching, *53
slot broach, *I48
Iver Johnson’s Arms and Cycle Works, 76
J
Jig for Square holes, *42, 43
wristpin keyway, 91
Joyce-Cridland Co., 72
K
II.3,
Key slot broach, *148
Keyway broach, double, *I 14
Solid type, *II.4, II5
broaches and bushings, *29
broaches, design of, III
in taper hole, 3o, *31
machine, Burton, 30, *31
machines, 13, *14, *I 5
Keyways, broaching, 26, *27
at right-angles, 28
broaching to a shoulder, 92, *94
double opposed, 26
spiral, 30, *32, 33, *34
time to cut, 26
Knowles machine, 13, *14, 4o, *41
L
Land for square broach teeth, *123
Lapointe, J. N., 126
two-spindle machine, 40, *41
Lapointe Co., J. N., 8
Lapointe, Frank J., 33, 39
Lapointe Machine Tool Co., 13
Largest broaching machine, 54, *55
Lathe, broaching spirals in, “Io2, Io.3
Laying out the teeth, 120
Lay-out for spline broaches, *I40, 141
Length of cutting edge on square broaches,
I 22
Lens grinding machine part, *91
Liddell, D. M., 197
Lifting jack parts, broaching, 72, *73, *74,
*76
Limit for size of round broach, II 7
Locomobile Co., 36
Lubricant for steel work, 63
vacuum bolt oil, 67
Lucas, J. L., I88
Lucas power press, 70, *71
M
Machine, pull type, 8, *g, *Io, *II, *12, 13,
:k ::
I4, "I 5
Machines, screw-operated, 8, *g, *Io, *II,
*I2, I3
Machining broaches, Alco practice, I 33
multiple-spline broaches, 200
pull broaches, IQI
push broaches, 198
spline broaches, *136, 138
Making broaches, IQI
Mandrel press as a broaching machiné, 85,
*88, *90, 92, *94, *95
Marathon Motor Works, 36
McCarter, Charles H., IoI
McDermid, H. B., 99
Metalwood Mfg. Co., *21, *22, 23
Milling, angular taper broach, IQ7
broach teeth, *136, 138, * 195, * 196
shank slot, *196, 197
Mossberg, Frank, 85
Motorcycle gears, broaches for, 145, *146
Motor drive machine, *II
Muehlmatt, Adolph, 96
N
Notched teeth, advantage of, 137
Notching teeth, 123, *136, 137
Number of broaches to use, IIo
O
Original uses of broaches, 2
Outboard broach support, *g, *Io, * 12
22O
INDEX
P
Packard Motor Car Co., 71
Pair of peculiar broaches, 188, *189
Paracentric slot broach, *148
Pawtucket Mfg. Co., 13
Pierce Cycle Co., 145
Pitch, differential, Ioff, I I I, *147, 148
formula for, Ioé
of teeth, differential, 5
Planer, broaching on, 99, IoI, *Io2
Planing broach blanks, 192, *193, *194
Pletz, A. C., 92
Prentiss vise, broaching body of, *45
Pressure for push broaching, 69, 71
Production on broached work, 63
Poppet heads, broaching, *53, 54
Power for broaching, 51
required for cored hole, 126
for push broaching, 190
Pull broaches, design of, Ioë
broaching, vertical, 59, *61, *62
work and practice, 26
type of broaches, 5, *6, *7
of machine, 8, *g, *Io, *II, *I 2, 13,
*I4, *I 5 -
Punching, I
Push broaches, 5, *7
design of, I57
broaching machines, 16, *17, *18, *19,
20, *21, *22, 23, *24, *25
work and practice, 66
R
Rack-and-pinion machines, 13, *14, *15
Rack cutting, 85, *86
Ratchet, internal, *.5o, 51
Reaming and broaching compared, 37
Rectangular broaches, 5
holes, 43, *44, *45
Relief of roughing broach, 120
Removing burrs with broach, *I 18, 119
Reserve teeth on a broach, I44
Revolver frame broaching, 76, *78
Round broaches, design of, II6
-cornered square hole, broaches for,
*I99
holes, broaching, 33, *34
Rudge-Whitworth shop, 36
S
S. A. E. recommended practice, 209 to 214
Salem Iron Works, 28
Saw and broach, difference between, I
file in same class, I
Scrap from broaching, 3
Screw-operated machines, 8, *9, *Io, *II,
*I 2, 13
vertical press, 23, *24
Seventy-five-ton hydraulic press, *19, 20
Shaper, broaching on, 97, *98, 99,”Ioo
keyway cutting in, 97, *98
Shoulder, broaching to, 92, *94
cutting to, I
Single tooth broaches, 81, *83
Six-spline broaches, pull type, I29,
*I32, 133
Slot in shank, milling, *196, 197
Smith & Mills Co., 97
Soap compound for cast iron, 39
Solid key broaches, I45, *I46
broaching, *73, 75, *76
Spacing, differential tooth, Ioë, III, *I47,
* I48
Speeds of machines, 8, 13, 15, 16, 20, 23
Spicer Mfg. Co., 66, I58, 198, 203
Spiral broaching in a lathe, *Io2, Io.3
keyways, 30, *32, 33, *34
Spline broach data table, I42
design, I34
broaches, making blank, *14o, I4I
upkeep, I43
fitting tables, 209 to 214
Splined steel gears, *47
Square broach data table, I 2I
broaches, design of, II9, I2O
holes, broaches for, 182, *184
broaching, 4o, *41
saving time in broaching, “I 29
Squaring ends of rods, 57, *58
Staggering teeth, *136, 137
Standard drawing for round broach, II6,
*II.8
for spline broach, *14o,
I4 I
for square broach, *I 26
types of machines, 8
Standard Machinery Co., 23, *24
Steel used for broaches, I45, I86, 191, 202
work, push broaches for, Ig8
Stroke of machines, 8, 12, 13, I5, 16, 20, 22,
23
Sub-press for cams, 81, *82
for gears, 75, *77
Sub-presses for broaching work, 75, *77, 81,
*82, 87, *88, *89
*I31,
INDEX
22 I
Summers, S. E., 180
Support, broach, outboard, *g, *Io, *I 2
for broach, *g, *Io, * 12, *35, *41, *44,
II 7
self-sustained, *I 2
Surfacing work, 99, *Ioo
Suverkrop, E. A., 77, 149, 191
T
Table for pitch of teeth, Io'7
of round broach sizes, II 7
Taper hole, keyway in, 3o, *31
Tapered square holes, 41, *42
Tearing, prevention of, *136, 139
Teeth, inserted broach, 5, *7
milling broach, *195, *196
number in work, 4o
Ten-spline broaches, *199
-ton hydraulic press, *22, 23
Testing depth of cut per tooth, 207
Textile machine parts, *53, 54
Thirty-five-ton Metalwood press, *21, 23
Time required for broaching, 63
Tools carried in a turret, I
Tooth load allowable, II 5
Turning long, slender broaches, 191, * 192
Turret broaching 92, *93, *94, 99, *Ioo,
Io.3, *Io4, *Io5
machine for small square holes, Io4,
*Io5
Two-Spindle machine, *Io, I 2, 13
Types of broaches, 5
of machines, standard, 8
Typical screw-operated, pull broaching
machine, *9
AUG 3 ()
U
Universal joints, broaching, 66, *67, *68
Unusual broaching job, *56
Upkeep of Spline broaches, 143
Uses of broaching tools, 2
V
Vacuum bolt oil for lubricant, 67
Valves, gun recoil, broaching, Io9, *Io4
Vertical machines, 16, *17, *18, *19, 20,
*21, *22, 23, *24, *25
pull-broaching machines, 59. *61, *62
screw press, 71, *72
Vincent Steel Process Co., 40
Wise bodies, broaching, 43, *44, *45
W
Walker Co., H. J., 4o
Watson-Stillman Co., 16
press, *17, 66, *67, *68, 81, *83
Weight of largest broaching machine, 54
Weights of machines, 8, 13, 15, 16, 23, 24
Westinghouse Electric & Mfg. Co., 178
Whiton rack cutter, *195
Williams, L. A., Io'7
Winton Motor Co., 48
Work adapter for broach, *II 2
bushings or holders, 154, *I 55, *156
Wrench work, 77, *79, *8o, *82, *86
Wristpin keyway, *91
1918
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