The result is that the average requirement of such a group is
but a fraction of the sum of the maximum requirements of the

1 Mechanical bell shifters were fitted to the cone pulleys of the Cornell Univer-
ity shop by Dr. Sweet nearly forty years ago.



150 METHODS OF MACHINE SHOP WORK

individual tools. Under the group system advantage may be
taken of this by installing a motor whose normal capacity is
equal to the average requirement of the machines to be driven
by it. Under the individual motor system, on the other hand,
we have several much smaller motors of much greater aggregate
capacity, the first result being much higher initial cost.
Moreover, since the large group motor works under its normal
load, or very near it, its efficiency is high, while since, at any one
time, most of the individual motors work under loads much
below their normal, their efficiency is low, the second result
being a greater consumption of current and the necessity for a
power plant of greater capacity.

In addition to the cloud under which it unjustly rests, there
are serious physical difficulties in the way of the revival of
cone-pulley driving. Wisely, or unwisely, many customers
want individual motor-driven machines and many modern
shops are laid out with its use in view. Machine-tool makers
cannot be criticised for supplying machines to suit the demand,
and, with the constant-speed pulley drive equally adapted,
without change, to individual motor or line shaft driving, the
reason for its popularity is apparent. Such influences as these
are the chief determining factors, to the exclusion of considera-
tions of the fundamental merits of the rival systems.



CHAPTER VIII

TURNING AND BORING

The primitive engine lathe Lathes for work of large diameter and
great length The boring mill, plain and turret The turret lathe
Special tools and their cost The collet chuck The pilot bar Reamers
and reaming The automatic turret lathe The magazine feed The
multiple spindle automatic turret lathe The multaumatic machine The
Fay and Lo-swing lathes The three types of boring bars and their uses
Taper and spherical boring bars Vertical boring machines for large
engine cylinders.

THE FIRST SCREW-CUTTING LATHE

The engine or screw-cutting lathe of to-day is the direct
descendant of the machine shown in Fig. I27 1 which was made
by Henry Maudsley about 1800 and was the first to embody
principles that are now universal. Prior to Maudsley's time,
lathe tools were controlled by the hand alone, after the manner
of small-speed lathes of to-day. Like all great inventions, the
slide rest which here appears was anticipated by the work of
others but not effectively, while the connecting of the work
spindle and lead screw by change gears, whereby screw cutting
was made possible, appears in none of these anticipations.
Maudsley is thus commonly and correctly credited with the
invention of the slide rest. As the author interprets Maudsley's
work, however, the invention was of wider scope than this,
for he invented other machine tools embodying the same
essential principle which, broadly speaking, was the mechanical
control of cutting tools, in which large field his only effective
anticipation was the boring bar of Wilkinson which preceded
the lathe.

Maudsley was also the first to cut good screws and substan-
tially all the screws of to-day are the lineal descendants to the
nth generation of those made by him. He made a machine 2

1 The lathe is now preserved at South Kensington Museum.

2 Also preserved at South Kensington Museum.

151



152 METHODS OF MACHINE SHOP WORK

for originating screws and from his time until the present day
improvement in the accuracy of screws has been brought about
chiefly by beginning with the best screw available as a lead
screw and cutting others from it by devices which corrected its
errors. Modern refined methods of doing this have already
been given. True, other than Maudsley's methods of originat-
ing screws have been devised and used for precision purposes,
but, measured by the number of their progeny, their influence




FIG. 127. Maudsley's original screw cutting lathe.

has been small compared with that of his screws. Small
screws are also still occasionally made by the use of hand
chasers and such screws have no, or, at most, a remote con-
nection with Maudsley's, but they are small in size, number
and importance.

Maudsley was the first great mechanic in the modern sense.

LARGE LATHES AND BORING MILLS

It is not the author's purpose to discuss engine lathe work
in general with which the reader is presumed to be familiar.



TURNING AND BORING



153



To those accustomed to work of small and medium sizes the
forms taken by lathes for large work are somewhat surprising.
For work of large diameters and relatively short length the
machine becomes a pit lathe of which a fine example from the
works of the Mesta Machine Company is shown in Fig. 128.

When positive truth is required in turned work there is no
method of mounting it equal to that of placing it on a mandrel
as in the present example. Pit lathes, however, are somewhat




FIG. 128. Pit lathe at work.

slow and the weight of heavy pieces makes their placing in
position troublesome. For work of large diameter a much more
common machine is the boring mill, of which one of twenty feet
swing, by the Betts Machine Company is shown in Fig. 129.
Boring mills of large size are frequently made as extension mills
the housings being arranged to be drawn back on the base in
order to increase the capacity. Such an extension mill, also
by the Betts Machine Company, of sixteen feet swing with the
housings in their forward and of twenty-four feet in their rear-



154



METHODS OF MACHINE SHOP WORK




FIG. 129. Twenty-foot boring mill.




FIG. 130. Sixteen-twenty-foot extension boring mill.



TURNING AND BORING



155




156 METHODS OF MACHINE SHOP WORK

ward position is shown in Fig. 130. In order to reach the
center of the table when the housings are run back, an auxiliary
removable arm perpendicular to the cross rail is provided.

Unlike all other machine tools the boring mill developed
from the top downward. Its chief advantage over the pit
lathe is that the work does not have to be chucked in opposition
to its own weight. Lying as it does on the face plate of the
machine, a piece may be adjusted, without the difficulty that
attends the adjustment of heavy work in the lathe. It
was, therefore, first developed of large size for heavy work,
the realization of its advantage over the lathe leading to its
later production in progressively smaller and smaller sizes and,
ultimately, with the addition of a turret for the production of
repetition work.

For work of large size combined with great length the gun
lathe shown in Fig. 131 from the Washington Navy Yard will
serve as an example. This lathe, by the Niles-Bement-Pond
Company, was built especially for the construction of the largest
guns. The great length of the lathe is due to the necessity for
accommodating the boring bar, since the lathe bores as well as
turns the guns. The accommodation of this bar requires the
lathe to be about twice as long as it would be were it required
to take in the gun only.

THE PLAIN TURRET LATHE

The adaptation of the lathe to the manufacturing system is by
the turret lathe which originated with the Jones and Lamson
Machine Company in 1855.

A simple turret lathe by the Warner and Swasey Company
the principle being the more obvious because of the simplicity
of the machine shown is illustrated in Fig. 132. The basic idea
of this and of all turret lathes is to preserve the setting of the
tools for a succession of pieces. In the use of the engine lathe
having a single tool post, each finishing tool is of necessity
adjusted with great nicety as each cut is taken but, when the
next cut is taken, the tool must be removed and the setting
destroyed. The turret lathe preserves the setting when once
made by providing a revolving turret having several holes in



TURNING AND BORING 157

which are inserted suitable tool holders. After a cut is finished,
the turret is revolved a step, thereby presenting the next
tool to the work without destroying the adjustment of the first,
which remains ready for the next piece when its turn comes. In
addition to thus duplicating the diameters of the work, the
lengths of the various cuts are positively determined by a series
of adjustable stops which are seen projecting from the right
of the turret slide. These stops form a lantern which revolves.




FIG. 132. Turret lathe,

step by step with the corresponding movements of the turret, in
order that they may be presented, one by one and in proper
order, to a stationary stop below the turret slide.

The lathe shown has a hole lengthwise through its spindle to
adapt it for work from the bar, as the expression is a bar of
rough stock passing through the spindle and being pushed for-
ward and then gripped in the chuck by the lever and other
mechanism at the left after each piece has been finished and cut
off. For this latter purpose a tool slide having a crosswise move-
ment only, although adjustable lengthwise of the lathe, is pro-
vided. This slide is fitted with two tool posts, of which the
one in the rear, fitted with an inverted tool, may be used for
cutting a recess, rounding a corner, etc.



158



METHODS OF MACHINE SHOP WORK





TURNING AND BORING 159

The turret lathe was originally made for the production of
small pieces screws, studs, pins, etc., from the bar, but it has
been progressively enlarged until machines are now to be made
capable of taking bars of stock of eight inches diameter through
their spindles. Meanwhile, another adaptation has been made
by the provision of suitable work holding chucks whereby sepa-
rate castings and forgings may be handled and, on top of this,
both types of machines are now made to perform all their func-
tions automatically, the work of the operator being not much
more than keeping them supplied with stock.

THE TURRET BORING MILL

The turret principle is also applied to boring mills of small
and medium sizes, such machines being frequently called ver-
tical turret lathes. A machine of this type by the Bullard
Machine Tool Company is shown in P'ig. 133. A supplementary
cross-slide turret capable of carrying four tools forms an addi-
tional feature of this machine and of others.

In this machine a departure is made from the usual construc-
tion of the stops. As was explained in connection with Fig.
132, the stops are commonly mechanical and positive the
moving stop abutting against its stationary mate. Instead
of this construction, visual or observation stops are here used.
Large micrometer dials carrying adjustable indexes are attached
to the feed screw shafts, the sizes of the work being determined
by the matching of these indexes against stationary indexes as
shown in Fig. 134. To avoid confusion the faces of the turret
are numbered, as are the indexes. The sizes of work dealt with
make the use of the usual special tools set for the outer diameters
impracticable. The tools used are therefore of the nature of
those used in engine lathes, the outer diameters as well as the
lengths of the pieces made being determined by the observation
stops.

The general method of tooling the machine and attacking the
work, combined with the use of the two turrets, is shown in Fig.
135. Except for the use of tools of the lathe type for the outer
diameters, this illustration will also serve to show the application



160



METHODS OF MACHINE SHOP WORK



of the turret principle to small as well as large work. Two
settings for the opposite sides of the fly wheel are shown, the
work of the second side being shown in the two right-hand
views.

A prominent example of the turret lathe is found in the flat
turret lathe of the Jones & Lamson Machine Company, which is
the legitimate successor of the original turret lathe. In this
machine, Fig. 136, the turret is a flat turn table carrying the tool
holders upon its top instead of about its periphery. These tool



Turret Lay-
out 2- Opera t,
2 nd 'Setting



urret Lay
out 8- Ope ra-
tions I st
Setting



7 th Operation 2 Opera tion




3 "* Operation 6 fh Operation



2 na Opera tion

FIG. 135. Representative arrangement of turret tools.



holders are so designed as to take simple turning and boring
tools, somewhat after the manner of the tool post of an engine
lathe and thus reduce the amount of tool making required and
adapt the machine to the production of parts in small lots. In
addition to this, long pieces may be made as, there being nothing
in the way to prevent, the turret may pass under such a piece
without interference. Another feature is the mounting of the
head stock upon a cross slide which performs the functions of
the cross slide of an engine lathe and permits facing, necking and
internal undercutting to be done.



TURNING AND BORING 161

This machine, like others that follow, is driven by the con-
stant-speed pulley system. The pulley is shown at the left
of the head stock which forms the gear box. Within it is a sys-
tem of change gears which are manipulated by the projecting
hand levers.

The cutting tools and their holders for turret lathes are more
or less special and made for the particular piece of work to be
produced. This is true of all processes for manufacturing parts
in lots. 1




FIG. 136. Flat turret lathe.

The cost of such tools must obviously be returned through the
saving which they accomplish this remark applying not only
to the cutting tools but to other special equipment which is
characteristic of the manufacturing system.

RELATION OF COST AND SAVING DUE TO SPECIAL TOOLS

Very little has been published from which the principles fol-
lowed by manufacturers in determining the justifiable expense
of an equipment for any particular case can be deduced and,
indeed, it would appear that not many manufacturers have

1 In the case of the turret lathe, especially the flat turret lathe, special tools
are much less required than formerly.
11



162 METHODS OF MACHINE SHOP WORK

definite rules for this work, the common procedure being to
determine the nature of the equipment by the exercise of simple
judgment. In the case of pieces made in large numbers, for
example in gun, sewing machine, and typewriter work, the
judgment of a competent man in this connection is usually
sufficient. In work of this character the saving produced by an
equipment is repeated such an enormous number of times, that
even a trifling saving on each piece multiplied by the number of
pieces made, produces a total which justifies any equipment
within reason.

The pinch comes in connection with work produced in smaller
numbers in which the saving on one piece is repeated a limited
number of times. In work of this kind the cost of the
equipment must be considered in relation to the saving due to
it and, for such work, the author adopted a rule many years ago
that the estimated saving due to a given special equipment
should return its estimated cost in one year's time and that if it
failed to promise such a return it should not be made. This
rule will impress most readers as extremely drastic and it was,
indeed, made drastic for special reasons. There are, however,
reasons of perfectly general application which make it necessary
that such a rule should be more drastic than would at first
sight appear. The rule is based upon estimated cost and
estimated savings. One sometimes goes wrong in his estimates
and, more often than not, the error is in the wrong direction.
Moreover, one never knows when an improvement will come
along which will lay a fine lot of special tools on the scrap heap.
If a set of tools continues in use four years, which is longer than
the average, they must earn twenty-five per cent, per annum
to replace themselves and they must also earn enough to keep
themselves in repair and it is not until they have done these
things that profit begins. For these reasons the author is
convinced that, as a general rule, subject to occasional reduc-
tion in cases where there is little probability of revolutionary
improvements, special tools should return by their savings not
less than fifty per cent, of their cost per annum. On the other
hand, in an industry which is in process of rapid development,
this percentage should be increased.



TURNING AND BORING



163



Whatever the percentage adoped, a rule in this form is of
perfectly general application. It takes account not only of the
size of the lots and of the lost time due to setting up and adjust-
ing the machines, but also of idle periods between lots, regardless
of their length.

THE COLLET CHUCK

An important feature of the turret lathe is the collet chuck,
shown in its original form in the section of the head stock of a
precision bench lathe by Hardinge, Brothers in Fig. 137 the
chuck proper being shown to an enlarged scale below thela the
head stock. The spindle of the lathe is bored and the end of the








x"' x *^ \


/WWVV\A\VK.








] r




wvwvww/*


_l__jr_L-_ >


\










FIG. 137. Collet chuck.

chuck is turned to an angle. The chuck is split by three radial
slots and has a threaded portion at its rear. A tube a is
threaded to fit the threads on the chuck and carries at its left a
hand wheel. The turning of the hand wheel draws the chuck
within the lathe spindle and closes its jaws upon the work. 1

1 The collet chuck was originally designed for watch and watch tool work.
From a capacity suitable for work of this character it has grown step by step
until it has been made capable of taking in solid steel bars of eight inches diameter
suitable for locomotive crank and cross-head pins.



164



METHODS OF MACHINE SHOP WORK



In the adaptation of the chuck to large work a number of
modifications have been made. In the form shown in Fig. 137
it is known as the draw-back collet chuck. In some cases the





FIG. 139. Modified collet chuck.

taper is reversed, resulting in the push-out chuck shown in Fig.
138 from a Bardons and Oliver turret lathe from which the
modification will be apparent. The gripping action in this case



TURNING AND BORING



165



is no longer by the hand wheel shown in Fig. 137, which is only
used in connection with work of small and moderate size. The
gripping is here through the bell cranks a, b, the sliding collar c,




FIG. 140. Collet chuck for work of large diameter.





FIG. 141. Construction of chuck shown in Fig. 140.

the tube d, and the connected mechanism. In the act of
gripping the work the draw-back chuck draws the piece toward
the head stock a slight distance. Frequently this is of no



166 METHODS OF MACHINE SHOP WORK

importance but in cases in which pieces are required to be of an
exact length it interferes with this requirement. In turret-
lathe work from the bar the length is gaged by pushing the bar
through the lathe spindle until it abuts against a stop in the first
hole of the turret. With the bar thus abutting, the push-out
chuck cannot disturb its position and for such work it is some-
times necessary and usually to be preferred.

By a suitable modification of its construction the chuck has
been adapted to the chucking of separate castings or forgings
of considerable size. Fig. 139 shows such a modification of the
draw-back chuck, this illustration also being from Bardons and
Oliver. The collet a carries false jaws b which are adapted to
the diameter of the work to be done. The closing of the jaws
is accomplished by the action of a tube through the spindle of
the lathe, but for still larger work this becomes impracticable
and the construction of Figs. 140 and 141 is adopted. In this
case the increased diameter leads to the introduction of an in-
creased number of cuts in the collet which are made alternately
from the two ends. The closing of the collet is by the action
of the outer threaded ring on the body of the chuck. In this as in
the last construction the work is seldom gripped directly by the
collet faces. False jaws are usually inserted in the collet and
are bored to suit the work to be done.

THE PILOT BAR

An important feature of turret-lathe equipment, known as the
pilot bar, was introduced by the Gisholt Machine Company.
The action of this appliance will be understood from Figs. 142
and 143, although these illustrations are not from a Gisholt
lathe. The work in progress is the turning of the face of a bevil
gear blank a by means of the broad-faced tool b, in Fig. 142
without and in Fig. 143 with the pilot bar c. In Fig. 142 thf
strain due to the pressure of the cut, starting at the arrow d,
follows the dotted line through the tool support, the lathe bed,
the spindle, and the work to the reaction arrow e. This round-
about course of the strain leads to spring and chatter which
are largely eliminated by the use of the pilot bar as shown in Fig.



TURNING AND BORING



167



143, in which the dotted line again shows the path of the strain
due to the pressure of the cut. With this construction the strain
does not reach the frame of the machine at all, the more limited
area which it occupies and the reduced leverage by which it




FIG. 142. FIG. 143.

Principle of the pilot bar.




FIG. 144. Use of the pilot bar.

acts serving to greatly reduce its effect and to increase the capac-
ity for heavy work.

The pilot bar is more frequently made to support the cutting



168



METHODS OF MACHINE SHOP WORK



tool , thereby, in another way, increasing the capacity for heavy
cuts. Such a use of it is shown in Fig. 144 which illustrates a
heavy turret lathe by the Niles-Bement-Pond Company. In
this case the tool for boring a gear blank is inserted in the middle
of the pilot bar which, fitting a suitable bush in the work-holding
chuck, is much more favorably supported to resist the strains
upon it than if the bar were cut off just beyond the tool.

REAMERS AND REAMING

An important tool in turret-lathe equipment is the reamer by
which the sizes of holes are finished and maintained uniform.




FIG. 145.





FIG. 146.



FIG. 149.



FIG. 147





FIG. 148.



Various forms of reamers.



FIG. 150.



A collection of reamers of various types adapted to various uses
and conditions is shown in Figs. 145-150. Fig. 145 shows a
fluted reamer, called chucking reamer, in which the reamer and
its shank are in one piece. The reamer is slightly tapered at



TURNING AND BORING 169

its outer end, the cutting action being upon the sides. As the
size increases the reamer is made with a hole through it, and
its shank is made of a separate piece. Such reamers, shown
in Fig. 146, are called shell reamers. Their action is precisely
the same as that of the tool shown in Fig. 145.

A tool having somewhat the appearance of the fluted reamer
but an entirely different action is shown in Figs. 147 and 148,
the tools referred to being called rose reamers. As before, the
small sizes are made integral with their shanks while larger ones
are separate. The flutes of these tools, while in appearance like
those of the previous reamers, are essentially different in that
they do no cutting. The cutting is entirely at the end of the
reamer, the flutes being provided as channels for the chips.
Of these two types, the fluted reamer is commonly used for the
last or sizing cut for which, if in good condition, it gives a beauti-
fully finished as well as a true surface. The rose reamer is
used as a preparatory tool, its cut being taken just previous
to that of the fluted reamer. The size of the two differs enough
to give a light finishing cut for the final operation.

Because of its light duty the fluted reamer will remain sharp
and maintain its size a long time but, ultimately, it becomes
dull and, when sharpened, its size is reduced. To meet this
condition a large amount of ingenuity has been expended in
devising adjustable or expansion reamers which are of two types.
The first type is intended to be expanded or contracted to
accommodate small changes in the diameter of the work,
usually by a screw adjustment, while the second type is intended
to be expanded before regrinding, then ground to its original
size and used as before, precisely as though it were a solid
reamer this operation being repeated at each regrinding.
While some will dispute the statement, the author believes,
nevertheless, that the first type of reamer is not, in most hands,
a success while the second type is a success.

An expansion reamer of the second type is shown in Fig. 149.