this station of the turret, being held in the turret hole. This tool has
a pilot bar and a holder which contains a facing blade. Feeding by hand,
as before, the tool is adjusted lengthwise so as to rough-face the work
to the dimension desired. In a similar way the finish-turning and
facing tools for the second position of the turret are set, the
cam-shaft being revolved by hand to bring this second face and second
cam into the working position. (The finish-facing tool is not shown in
place in Fig. 36.)
[Illustration: Fig. 38. Diagram of Cross-slide Cams and Feeding
Mechanism]
=Setting the Cross-slide Cam.=--As previously mentioned, the third
turret face has no tool, the cutting off of the collar being done during
this part of the cycle of operations. It has been taken for granted that
in setting the turret slide, room has been left between it and the chuck
for the cross-slide. The cross-slide is clamped in a longitudinal
position on the bed, convenient for the cutting-off operation, which is
done with a tool _D_ (Fig. 36) in the rear toolpost, thus leaving the
front unobstructed for the operator. When both forming and cutting off
are to be done, the forming tool is generally held at the front and the
cutting-off tool at the back because heavier and more accurate forming
can be done with the work revolving downward toward a tool in the front
toolpost, than with the tool at the rear where it is subjected to a
lifting action.
The arrangement of the cross-slide cams is shown in Fig. 38, which is an
end view of the large drum _E_, Fig. 32. The rear feed cam is the one to
be used, and since this cutting-off operation is a short one, it may be
done during the return of the turret for position No. 3. The cam drum
is, therefore, rotated by hand until the turret face No. 3 has begun to
return. The cross-slide cams are then loosened and the rear feed cam is
swung around to just touch the roller _R_ which operates arm _A_, the
cross-slide having been adjusted out to nearly the limit of its forward
travel, leaving approximately enough movement for cutting off the
collar. The rear feed cam is then clamped in this position.
A cutting-off tool is next placed in the rear toolpost at the proper
height. The rear toolpost slide is then adjusted to bring the point of
the cutting-off tool up to the work, and the cam drum is revolved by
hand until the piece is cut off. The cross-slide tool is, of course, set
in the proper position to make a collar of the required thickness.
Feeding by hand is discontinued when the roll is on the point of the
cam; the cutting-off tool slide is then permanently set on the
cross-slide so that the point of the cutting-off tool enters the bore
just far enough to completely sever the collar from the bushing. The
motion of the cam drum is continued, by hand, until the roll is over the
point of the feed cam. The cross-slide is then pushed back, by hand,
until the cam and roll are again in contact, when the return cam is
brought up and clamped in position, so that there is just room for the
roll between the feed cam and the return cam. The rear return cam (as
the hand feed of the cam drum is continued) brings the cross-slide back
to its central position. Since there is no front tool used for this
series of operations (although a tool is shown in the front toolpost,
Fig. 36), the first feed and return cams are allowed to remain wherever
they happen to be. These cam adjustments can all be made from the front
of the machine.
=Setting the Boring Tool for Recessing.=--The feeding of the turret
slide is now continued to make sure that the cutting-off tool is
returned to its normal position before the facing tool in the next face
of the turret begins to work. The facing of the bushing, so far as the
setting of the tool is concerned, is merely a repetition of the facing
operation at the first position of the turret. The recessing tool is
next set. This tool, which is shown diagrammatically in Fig. 39, is very
simple as compared with the somewhat complex operation it has to
perform. This recess is for clearance only, and accurate dimensions and
fine finish are not necessary. The recessing tool consists simply of a
slender boring-bar held in the turret and carrying a cutter suitably
located about midway the bar. The forward end of the bar is small enough
to enter a bell-mouthed bushing held in the chuck. The boring-bar is
bent to one side far enough so that the cutter clears the hole as the
bar enters, but is forced into the work as the rounded hole of the
bushing engages the end of the bar and deflects it into the working
position. The upper diagram shows the position of the bar as it enters
the hole, and the lower one the position after it has entered the
bushing and is engaged in turning the recess. This bar is set in the
turret so that at the extreme forward travel of the turret slide, the
recess will be bored to the required length. The cutter must also be
adjusted to bore to the desired diameter. This completes the setting of
the cutting tools.
[Illustration: Fig. 39. Flexible Boring Tool used for Recessing a
Bushing in Automatic Chucking and Turning Machine]
=Adjustments for Automatic Feed and Speed Changes.=--The machine must
now be set to perform automatically the desired changes of spindle speed
and the fast and slow cam movements for the tools. After placing a new
piece of work in the machine (the first one having been completed in the
setting-up operation), the cam-shaft is revolved by hand until the
turning tool in turret face No. 1 is just about to begin its cut. The
control wheel _D_, Fig. 34, is rotated in its normal direction until the
next graduation marked "slow" is in line with an index mark on the base
of the machine. Then the nearest pin _M_ is moved up until it bears
against a tooth of the star wheel (previously referred to) and is
clamped in this position. The pin should now be in the proper location,
but to test its position, rotate the cam shaft backward by hand and
throw in the automatic feed; then watch the cut to see if the drum slows
down just before the tool begins to work. If it does not, the pin should
be adjusted a little, one way or the other, as may be required. (In
going over a piece of work for the first time, it is best to have the
feed set to the smallest rate, feed change handle _K_ being in position
No. 1.)
After the cut has been completed and the turret feed cam-roll is on the
high part of the cam, the power feed should again be stopped and the
handwheel revolved until the next graduation marked "fast" is opposite
the index mark. The next stop pin is then moved up until it just touches
the star wheel, where it is clamped in position. The feed being again
thrown in, the turret will be returned rapidly, indexed, and moved
forward for the second operation. After stopping the automatic movement,
the pins are set for this face, and so on for all the operations,
including that in which the cross-slide is used for cutting off the
finished collar.
As the first, second, and third operations are on comparatively large
diameters, they should be done at the slow speed, handle _J_, Fig. 34,
being set to give that speed. While the turret slide is being returned
between operations 3 and 4, one of the spindle speed-changing dogs _N_
should be clamped to the rim of disk _D_ so as to change the spindle
speed to the fast movement. This speed is continued until the last
operation is completed, when a second dog is clamped in place to again
throw in the slow movement. The feed knock-off dog should also be
clamped in place on the disk to stop the machine at the completion of
the fifth operation, when the turret is in its rear position. This
completes the setting up of the machine. If the feed is finer than is
necessary, the feed change handle _K_ may now be moved to a position
which will give the maximum feed that can be used.
It has taken considerable time to describe the setting up of the machine
for this simple operation, but in the hands of a competent man it can be
done quite rapidly. While a simple operation has been referred to in the
foregoing, it will be understood that a great variety of work can be
done on a machine of this type. It is not unusual to see as many as ten
cutting tools operating simultaneously on a piece of work, the tools
being carried by the turret, cross-slide and back facing attachment. The
latter is operated from a separate cam applied to the cam-shaft and
acting through levers on a back facing bar which passes through a hole
in the spindle. In this back facing bar may be mounted drills, cutters,
facing tools, etc. for machining the rear face of a casting held in the
chuck jaws. Where extreme accuracy is required, a double back facing
attachment may be used, arranged with cutters for taking both roughing
and finishing cuts. The use of this attachment often saves a second
operation. This automatic chucking and turning machine is also adapted
for bar work, especially in diameters varying from 3 to 6 inches.
=Turning Flywheel in Automatic Chucking and Turning Machine.=--A typical
operation on the Potter & Johnston automatic chucking and turning
machine is illustrated in Fig. 40, which shows the machine arranged for
turning the cast-iron flywheel for the engine of a motor truck. The rim
is turned and faced on both sides and the hub is bored, reamed and faced
on both sides. The flywheel casting is held in a chuck by three special
jaws which grip the inside of the rim. The order of the operations is as
follows:
The rear end of the hub is faced by the back facing bar; the cored hole
is started by a four-lipped drill in the turret and the front end of the
hub is rough-faced. (These tools are on the rear side of the turret
when the latter is in the position shown in the illustration.) After the
turret indexes, the hole is rough-bored by tool _A_ and while this is
being done, the outside of the rim is rough-turned by tool _B_ held in a
special bracket attached to the turret. Both sides of the rim are also
rough-faced by tools _C_ and _D_ held at the front of the cross-slide,
this operation taking place at the same time that the rim is turned and
the hole is being bored.
[Illustration: Fig. 40. Machining Flywheels in Potter & Johnston
Automatic Chucking and Turning Machine]
The turret again automatically recedes and indexes, thus locating bar
_E_ and turning tool _G_ in the working position. The hole is then
finish-bored by tool _E_ and the hub is finish-faced by blade _F_; at
the same time the rim is finish-turned by tool _G_ and the sides are
finish-faced to the proper width by two tools held at the rear of the
cross-slide. The turret automatically recedes and indexes a third time,
thus locating the flat-cutter reamer-bar _H_ in the working position and
then the hole is reamed to the required diameter. This completes the
cycle of operations. The total time for machining this flywheel is forty
minutes.
=Automatic Multiple-spindle Chucking Machine.=--An example of the
specialized machines now used for producing duplicate parts, is shown in
Fig. 41. This is a "New Britain" automatic multiple-spindle chucking
machine of the single-head type and it is especially adapted for boring,
reaming and facing operations on castings or forgings which can readily
be held in chuck jaws. This particular machine has five spindles, which
carry and revolve the tools. The work being machined is held stationary
in the multiple chuck turret _A_ which holds each part in line with one
of the spindles and automatically indexes, so that the work passes from
one spindle to another until it is finished. The turret then indexes the
finished piece to a sixth or "loading position" which is not opposite a
spindle, where the part is removed and replaced with a rough casting.
Each pair of chuck jaws is operated independently of the others by the
use of a chuck wrench. These jaws are made to suit the shape of the
work.
[Illustration: Fig. 41. New Britain Multiple-spindle Automatic Chucking
Machine of Single-head Type]
When a single-head machine is in operation, the turret advances and
feeds the work against the revolving tools so that a number of pieces
are operated upon at the same time. The turret is fed by a cam drum _B_.
Cam strips are bolted to the outside of this drum and act directly
against a roller attached to the yoke _C_ which can be clamped in
different positions on the spindle _D_, the position depending upon the
length of the work. On the opposite end of the turret spindle is the
indexing mechanism _E_. An automatically spring-operated latch _F_
engages notches in the rim of the dividing wheel, thus accurately
locating the turret. The turret is locked by a steadyrest _G_, which,
for each working position, automatically slides into engagement with one
of the notches in the turret. This relieves the indexing mechanism of
all strain.
[Illustration: Fig. 42. Detail View of New Britain Double-head
Eight-spindle Machine, Boring, Reaming and Facing Castings]
This type of machine is also built with two spindle heads, the
double-head design being used for work requiring operations on both
ends. When the double-head machine is in operation, the revolving
spindles and tools advance on both sides of the chuck turret, the latter
remaining stationary except when indexing. The feed drums on the
double-head machine are located directly beneath each group of spindles.
Fig. 42 shows an example of work on a machine of the double-head design.
This is an eight-spindle machine, there being two groups of four
spindles on each side of the turret. The castings _E_ are for the wheel
hubs of automobiles. The order of the operations on one of the castings,
as it indexes around, is as follows: The hole in the hub is first
rough-reamed by taper reamer _A_ and the opposite end of the hub is
rough-faced and counterbored by a tool in spindle _A_{1}_. When the
turret indexes, this same casting is reamed close to the finished size
by reamer _B_ and the left end of the hub is rough-faced by cutter _F_,
while a tool in the opposite spindle _B_{1}_ finishes the counterboring
and facing operation. At the third position, reamer _C_ finishes the
hole accurately to size, and when the work is indexed to the fourth
position, the hub on the left side is finish-faced by a tool in spindle
_D_. (The third and fourth spindles of the right-hand group are not used
for this particular operation.) When the turret again indexes, the
finished casting is removed and replaced with a rough one. While the
successive operations on a single casting have just been described, it
will be understood that all of the tools operate simultaneously and that
a finished casting arrives at the unloading and loading position each
time the turret indexes. Three hundred of these malleable castings are
machined in nine hours.
=Selecting Type of Turning Machine.=--The variety of machine tools now
in use is very extensive, and as different types can often be employed
for the same kind of work, the selection of the best and most efficient
machine is often a rather difficult problem. To illustrate, there are
many different types and designs of turning machines, such as the
ordinary engine lathe, the hand-operated turret lathe, the
semi-automatic turning machine, and the fully automatic type, which,
after it is "set up" and started, is entirely independent. Hence, when a
certain part must be turned, the question is, what kind of machine
should be used, assuming that it would be possible to employ several
different machines? The answer to this question usually depends
principally upon the number of parts that must be turned.
For example, a certain casting or forging might be turned in a lathe,
which could be finished in some form of automatic or semi-automatic
turning machine much more quickly. It does not necessarily follow,
however, that the automatic is the best machine to use, because the
lathe is designed for general work and the part referred to could
doubtless be turned with the regular lathe equipment, whereas the
automatic machine would require special tools and it would also need to
be carefully adjusted. Therefore, if only a few parts were needed, the
lathe might be the best tool to use, but if a large number were
required, the automatic or semi-automatic machine would doubtless be
preferable, because the saving in time effected by the latter type would
more than offset the extra expense for tool equipment and setting the
machine. It is also necessary, in connection with some work, to consider
the degree of accuracy required, as well as the rate of production, and
it is because of these varying conditions that work of the same general
class is often done in machines of different types, in order to secure
the most efficient results.
CHAPTER VI
VERTICAL BORING MILL PRACTICE
All the different types of turning machines now in use originated from
the lathe. Many of these tools, however, do not resemble the lathe
because, in the process of evolution, there have been many changes made
in order to develop turning machines for handling certain classes of
work to the best advantage. The machine illustrated in Fig. 1 belongs to
the lathe family and is known as a vertical boring and turning mill.
This type, as the name implies, is used for boring and turning
operations, and it is very efficient for work within its range. The part
to be machined is held to the table _B_ either by clamps or in chuck
jaws attached to the table. When the machine is in operation, the table
revolves and the turning or boring tools (which are held in tool-blocks
_T_) remain stationary, except for the feeding movement. Very often more
than one tool is used at a time, as will be shown later by examples of
vertical boring mill work. The tool-blocks _T_ are inserted in tool-bars
_T_{1}_ carried by saddles _S_ which are mounted on cross-rail _C_. Each
tool-head (consisting of a saddle and tool-bar) can be moved
horizontally along cross-rail _C_, and the tool-bars _T_{1}_ have a
vertical movement. These movements can be effected either by hand or
power.
When a surface is being turned parallel to the work table, the entire
tool-head moves horizontally along the cross-rail, but when a
cylindrical surface is being turned, the tool-bar moves vertically. The
tool-heads are moved horizontally by the screws _H_ and _H_{1}_, and the
vertical feed for the tool-bars is obtained from the splined shafts _V_
and _V_{1}_, there being a separate screw and shaft for each head so
that the feeding movements are independent. These feed shafts are
rotated for the power feed by vertical shafts _A_ and _A_{1}_ on each
side of the machine.
These vertical shafts connect with the feed shafts through bevel and
spur gears located at the ends of the cross-rail. On most boring mills,
connection is made with one of the splined shafts _V_ or screw _H_, by a
movable gear, which is placed on whichever shaft will give the desired
direction of feed. The particular machine illustrated is so arranged
that either the right or left screw or feed shaft can be engaged by
simply shifting levers _D_{1}_ or _D_.
[Illustration: Fig. 1. Gisholt Vertical Boring and Turning Mill]
The amount of feed per revolution of the table is varied for each
tool-head by feed-changing mechanisms _F_ on each side of the machine.
These feed boxes contain gears of different sizes, and by changing the
combinations of these gears, the amount of feed is varied. Five feed
changes are obtained on this machine by shifting lever _E_, and this
number is doubled by shifting lever _G_. By having two feed boxes, the
feeding movement of each head can be varied independently. The direction
of either the horizontal or vertical feed can be reversed by lever _R_,
which is also used for engaging or disengaging the feeds. This machine
is equipped with the dials _I_ and _I_{1}_ which can be set to
automatically disengage the feed at any predetermined point. There are
also micrometer dials graduated to thousandths of an inch and used for
adjusting the tools without the use of measuring instruments.
The work table _B_ is driven indirectly from a belt pulley at the rear,
which transmits the power through gearing. The speed of the table can be
varied for turning large or small parts, by levers _J_ and _K_ and the
table can be started, stopped or rotated part of a revolution by lever
_L_ which connects with a friction clutch. There are corresponding feed
and speed levers on the opposite side, so that the machine can be
controlled from either position.
The heads can be adjusted along the cross-rail for setting the tools by
hand-cranks _N_, and the tool slides can be moved vertically by turning
shafts _V_ with the same cranks. With this machine, however, these
adjustments do not have to be made by hand, ordinarily, as there are
rapid power movements controlled by levers _M_. These levers
automatically disengage the feeds and enable the tool-heads to be
rapidly shifted to the required position, the direction of the movement
depending upon the position of the feed reverse lever _R_ and lever _D_.
This rapid traverse, which is a feature applied to modern boring mills
of medium and large size, saves time and the labor connected with hand
adjustments. The cross-rail _C_ has a vertical adjustment on the faces
of the right and left housings which support it, in order to locate the
tool-heads at the right height for the work. This adjustment is effected
by power and is controlled by levers at the sides of the housings.
Normally, the cross-rail is bolted to the housings, and these bolts must
be loosened before making the adjustment, and must always be tightened
afterwards.
The function of these different levers has been explained to show, in a
general way, how a vertical boring machine is operated. It should be
understood, however, that the arrangement differs considerably on
machines of other makes. The construction also varies considerably on
machines of the same make but of different size.
[Illustration: Fig. 2. Small Boring and Turning Mill with Single
Turret-head]
All modern vertical boring mills of medium and large sizes are equipped
with two tool-heads, as shown in Fig. 1, because a great deal of work
done on a machine of this type can have two surfaces machined
simultaneously. On the other hand, small mills of the type illustrated
in Fig. 2 have a single head. The toolslide of this machine, instead of
having a single tool-block, carries a five-sided turret _T_ in which
different tools can be mounted. These tools are shifted to the working
position as they are needed, by loosening binder lever _L_ and turning
or "indexing" the turret. The turret is located and locked in any of its
five positions by lever _I_, which controls a plunger that engages
notches at the rear. Frequently, all the tools for machining a part can
be held in the turret, so that little time is required for changing from
one tool to the next. Some large machines having two tool-heads are also
equipped with a turret on one head.
=Boring and Turning in a Vertical Boring Mill.=--The vertical boring
mill is, in many respects, like a lathe placed in a vertical position,
the table of the mill corresponding to the faceplate or chuck of the
lathe and the tool-head to the lathe carriage. Much of the work done by
a vertical mill could also be machined in a lathe, but the former is
much more efficient for work within its range. To begin with, it is more
convenient to clamp work to a horizontal table than to the vertical
surface of a lathe faceplate, or, as someone has aptly said, "It is
easier to lay a piece down than to hang it up." This is especially true
of the heavy parts for which the boring mill is principally used. Very
deep roughing cuts can also be taken with a vertical mill. This type of
machine mill is designed for turning and boring work which, generally
speaking, is quite large in diameter in proportion to the width or
height. The work varies greatly, especially in regard to its diameter,
so that boring mills are built in a large range of sizes. The small and
medium sizes will swing work varying from about 30 inches to 6 or 7 feet
in diameter, whereas large machines, such as are used for turning very
large flywheels, sheaves, etc., have a swing of 16 or 20 feet, and
larger sizes are used in some shops. The size of a vertical mill, like
any other machine tool, should be somewhat in proportion to the size of
the work for which it is intended, as a very large machine is unwieldy,
and, therefore, inefficient for machining comparatively small parts.
=Holding and Setting Work on Boring Mill Table.=--There are three
general methods of holding work to the table of a boring mill; namely,
by the use of chucks, by ordinary bolts and clamps, or in special
fixtures. Chucks which are built into the table (as illustrated in Fig.
2) and have both universal and independent adjustments for the jaws can
be used to advantage for holding castings that are either round or
irregular in shape. The universal adjustment is used for cylindrical
parts, such as disks, flywheels, gear blanks, etc., and the independent
adjustment, for castings of irregular shape. Chucks which have either an
independent or universal movement for the jaws are known as a
"combination" type and usually have three jaws. There is also a four-jaw
type which has the independent adjustment only. This style is preferable
for work that is not cylindrical and which must be held very securely.
Chuck jaws that do not form a part of the machine table, but are bolted
to it in the required position, are also employed extensively,
especially on comparatively large machines.
Most of the work done in a vertical mill is held in a chuck.
Occasionally, however, it is preferable to clamp a part directly to the
table. This may be desirable because of the shape and size of the work,
or because it is necessary to hold a previously machined surface
directly against the table in order to secure greater accuracy.
Sometimes a casting is held in the chuck for turning one side, and then
the finished side is clamped against the table for turning the opposite
side. Parts which are to be machined in large quantities are often held
in special fixtures. This method is employed when it enables the work to
be set up more quickly than would be possible if regular clamps or chuck
jaws were used.
Work that is to be turned or bored should first be set so that the part
to be machined is about central with the table. For example, the rim of
a flywheel should be set to run true so that it can be finished by
removing about the same amount of metal around the entire rim; in other
words, the rim should be set concentric with the table, as shown in Fig.
3, and the sides of the rim should also be parallel to the table.
[Illustration: Fig. 3. Plan View showing Flywheel Casting Chucked for
Turning]
A simple tool that is very useful for testing the position of any
cylindrical casting consists of a wooden shank into which is inserted a
piece of wire, having one end bent. This tool is clamped in the toolpost
and as the work revolves the wire is adjusted close to the cylindrical
surface being tested. The movement of the work with relation to the
stationary wire point will, of course, show whether or not the part runs
true. The advantage of using a piece of wire for testing, instead of a
rigid tool, is that the wire, owing to its flexibility, will simply be
bent backward if it is moved too close to a surface which is
considerably out of true. The upper surface of a casting can be tested
for parallelism with the table by using this same wire gage, or by
comparing the surface, as the table is revolved slowly, with a tool held
in the toolpost. An ordinary surface gage is also used for this purpose.
The proper surface to set true, in any case, depends upon the
requirements. A plain cylindrical disk would be set so that the outside
ran true and the top surface was parallel with the table. When setting a
flywheel, if the inside of the rim is to remain rough, the casting
should be set by this surface rather than by the outside, so that the
rim, when finished, will be uniform in thickness.
As far as possible, chucks should be used for holding cylindrical parts,
owing to their convenience. The jaws should be set against an interior
cylindrical surface whenever this is feasible. To illustrate, the
flywheel in Fig. 3 is gripped by the inside of the rim which permits the
outside to be turned at this setting of the work. It is also advisable
to set a flywheel casting in the chuck so that a spoke rests against one
of the jaws as at _d_, if this is possible. This jaw will then act as a
driver and prevent the casting from slipping or turning in the chuck
jaws, owing to the tangential pressure of the turning tool. When a cut
is being taken, the table and work rotate as shown by arrow _a_, and the
thrust of the cut (taken by tool _t_) tends to move the wheel backward
against the direction of rotation, as shown by arrow _b_. If one of the
chuck jaws bears against one of the spokes, this movement is prevented.
It is not always feasible to use a chuck jaw as a driver and then a
special driver having the form of a small angle-plate or block is
sometimes bolted directly to the table. Another method of driving is to
set a brace between a spoke or projection on the work and a chuck jaw or
strip attached to the table. Drivers are not only used when turning
flywheels, but in connection with any large casting, especially when
heavy cuts have to be taken. Of course, some castings are so shaped that
drivers cannot be employed.
=Turning in a Boring Mill.=--The vertical type of boring mill is used
more for turning cylindrical surfaces than for actual boring, although a
large part of the work requires both turning and boring. We shall first
consider, in a general way, how surfaces are turned and then refer to
some boring operations. The diagram _A_, Fig. 4, illustrates how a
horizontal surface would be turned. The tool _t_ is clamped in
tool-block _t_{1}_, in a vertical position, and it is fed horizontally
as the table and work rotate. The tool is first adjusted by hand for the
proper depth of cut and the automatic horizontal feed is then engaged.
When a cylindrical surface is to be turned, the tool (provided a
straight tool is used) is clamped in a horizontal position and is fed
downward as indicated at _B_. The amount that the tool should feed per
revolution of the work, depends upon the kind of material being turned,
the diameter of the turned part and the depth of the cut.
[Illustration: Fig. 4. (A) Turning a Flat Surface. (B) Turning a
Cylindrical Surface]
Most of the parts machined in a vertical boring mill are made of cast
iron and, ordinarily, at least one roughing and one finishing cut is
taken. The number of roughing cuts required in any case depends, of
course, upon the amount of metal to be removed. An ordinary roughing cut
in soft cast iron might vary in depth from 1/8 or 3/16 inch to 3/8 or
1/2 inch and the tool would probably have a feed per revolution of from
1/16 to 1/8 inch, although deeper cuts and coarser feeds are sometimes
taken. These figures are merely given to show, in a general way, what
cuts and feeds are practicable. The tool used for roughing usually has a
rounded end which leaves a ridged or rough surface. To obtain a smooth
finish, broad flat tools are used. The flat cutting edge is set parallel
to the tool's travel and a coarse feed is used in order to reduce the
time required for taking the cut. The finishing feeds for cast iron vary
from 1/4 to 3/4 inch on ordinary work. The different tools used on the
vertical mill will be referred to more in detail later.
All medium and large sized vertical boring mills are equipped with two
tool-heads and two tools are frequently used at the same time,
especially on large work. Fig. 9 illustrates the use of two tools
simultaneously. The casting shown is a flywheel, and the tool on the
right side turns the upper side of the rim, while the tool on the left
side turns the outside or cylindrical surface. As a boring mill table
rotates in a counter-clockwise direction, the left-hand tool is reversed
to bring the cutting edge at the rear. By turning two surfaces at once,
the total time for machining the casting is, of course, greatly reduced.
The turning of flywheels is a common vertical boring mill operation, and
this work will be referred to in detail later on.
[Illustration: Fig. 5. Tools for Boring and Reaming Holes]
=Boring Operations.=--There are several methods of machining holes when
using a vertical boring mill. Ordinarily, small holes are cored in
castings and it is simply necessary to finish the rough surface to the
required diameter. Some of the tools used for boring and finishing
comparatively small holes are shown in Fig. 5. Sketch _A_ shows a boring
tool consisting of a cutter _c_ inserted in a shank, which, in turn, is
held in the tool slide, or in a turret attached to the tool slide. With
a tool of this type, a hole is bored by taking one or more cuts down
through it. The tool shown at _B_ is a four-lipped drill which is used
for drilling cored holes preparatory to finishing by a cutter or reamer.
This drill would probably finish a hole to within about 1/32 inch of the
finish diameter, thus leaving a small amount of metal for the reamer to
remove. The tool illustrated at _C_ has a double-ended flat cutter _c_,
which cuts on both sides. These cutters are often made in sets for
boring duplicate parts. Ordinarily, there are two cutters in a set, one
being used for roughing and the other for finishing. The cutter passes
through a rectangular slot in the bar and this particular style is
centrally located by shoulders _s_, and is held by a taper pin _p_. Some
cutter bars have an extension end, or "pilot" as it is called, which
passes through a close-fitting bushing in the table to steady the bar.
Sketch _D_ shows a finishing reamer. This tool takes a very light cut
and is intended to finish holes that have been previously bored close to
the required size. Sometimes a flat cutter _C_ is used for roughing and
a reamer for finishing. The reamer is especially desirable for
interchangeable work, when all holes must have a smooth finish and be of
the same diameter. When a reamer is held rigidly to a turret or
toolslide, it is liable to produce a hole that is either tapering or
larger than the reamer diameter. To prevent this, the reamer should be
held in a "floating" holder which, by means of a slight adjustment,
allows the reamer to align itself with the hole. There are several
methods of securing this "floating" movement. (See "Floating Reamer
Holders.")
[Illustration: Fig. 6. Boring with Regular Turning Tools]
Large holes or interior cylindrical surfaces are bored by tools held in
the regular tool-head. The tool is sometimes clamped in a horizontal
position as shown at _A_, Fig. 6, or a bent type is used as at _B_. Cast
iron is usually finished by a broad flat tool as at _C_, the same as
when turning exterior surfaces. Obviously a hole that is bored in this
way must be large enough to admit the tool-block.
[Illustration: Fig. 7. Set of Boring Mill Tools]
=Turning Tools for the Vertical Boring Mill.=--A set of turning tools
for the vertical boring mill is shown in Fig. 7. These tools can be used
for a wide variety of ordinary turning operations. When a great many
duplicate parts are to be machined, special tool equipment can often be
used to advantage, but as the form of this equipment depends upon the
character of the work, only standard tools have been shown in this
illustration. The tool shown at _A_ is a right-hand, roughing tool, and
a left-hand tool of the same type is shown at _B_. Tool _C_ is an offset
or bent, left-hand round nose for roughing, and _D_ is a right-hand
offset roughing tool. A straight round nose is shown at _E_. Tool _F_
has a flat, broad cutting edge and is used for finishing. Left-and
right-hand finishing tools of the offset type are shown at _G_ and _H_,
respectively. Tool _I_ has a square end and is used for cutting grooves.
Right-and left-hand parting tools are shown at _J_ and _K_, and tool _L_
is a form frequently used for rounding corners.
[Illustration: Fig. 8. Diagrams Illustrating Use of Different Forms of
Tools]
The diagrams in Fig. 8 show, in a general way, how each of the tools
illustrated in Fig. 7 are used, and corresponding tools are marked by
the same reference letters in both of these illustrations. The right-and
left-hand roughing tools _A_ and _B_ are especially adapted for taking
deep roughing cuts. One feeds away from the center of the table, or to
the right (when held in the right-hand tool-block) and the other tool is
ground to feed in the opposite direction. Ordinarily, when turning plain
flat surfaces, the cut is started at the outside and the tool feeds
toward the center, as at _B_, although it is sometimes more convenient
to feed in the opposite direction, as at _A_, especially when there is a
rim or other projecting part at the outside edge. The tool shown at _A_
could also be used for turning cylindrical surfaces, by clamping it in a
horizontal position across the bottom of the tool-block. The feeding
movement would then be downward or at right-angles to the work table.
The offset round-nose tools _C_ and _D_ are for turning exterior or
interior cylinder surfaces. The shank of this tool is clamped in the
tool-block in a vertical position and as the bent end extends below the
tool-block, it can be fed down close to a shoulder. The straight type
shown at _E_ is commonly used for turning steel or iron, and when the
point is drawn out narrower, it is also used for brass, although the
front is then ground without slope. Tool _F_ is for light finishing cuts
and broad feeds. The amount of feed per revolution of the work should
always be less than the width of the cutting edge as otherwise ridges
will be left on the turned surface. The offset tools _G_ and _H_ are for
finishing exterior and interior cylindrical surfaces. These tools also
have both vertical and horizontal cutting edges and are sometimes used
for first finishing a cylindrical and then a horizontal surface, or
_vice versa_. Tool _I_ is adapted to such work as cutting packing-ring
grooves in engine pistons, forming square or rectangular grooves, and
similar work. The parting tools _J_ and _K_ can also be used for forming
narrow grooves or for cutting off rings, etc. The sketch _K_ (Fig. 8)
indicates how a tool of this kind might be used for squaring a corner
under a shoulder. Tool _L_ is frequently used on boring mills for
rounding the corners of flywheel rims, in order to give them a more
finished appearance. It has two cutting edges so that either side can be
used as when rounding the inner and outer corners of a rim.
The turning tools of a vertical boring mill are similar, in many
respects, to those used in a lathe, although the shanks of the former
are shorter and more stocky than those of lathe tools. The cutting edges
of some of the tools also differ somewhat in form, but the principles
which govern the grinding of lathe and boring mill tools are identical,
and those who are not familiar with tool grinding are referred to
Chapter II, in which this subject is treated.
=Turning a Flywheel on a Vertical Mill.=--The turning of a flywheel is a
good example of the kind of work for which a vertical boring mill is
adapted. A flywheel should preferably be machined on a double-head mill
so that one side and the periphery of the rim can be turned at the same
time. A common method of holding a flywheel is shown in Fig. 9. The rim
is gripped by four chuck jaws _D_ which, if practicable, should be on
the inside where they will not interfere with the movement of the tool.
Two of the jaws, in this case, are set against the spokes on opposite
sides of the wheel, to act as drivers and prevent any backward shifting
of work when a heavy cut is being taken. The illustration shows the tool
to the right rough turning the side of the rim, while the left-hand tool
turns the periphery. Finishing cuts are also taken over the rim, at this
setting, and the hub is turned on the outside, faced on top, and the
hole bored.
[Illustration: Fig. 9. Turning the Rim of a Flywheel]
The three tools _A_, _B_ and _C_, for finishing the hole, are mounted in
the turret. Bar _A_, which carries a cutter at its end, first rough
bores the hole. The sizing cutter _B_ is then used to straighten it
before inserting the finishing reamer _C_. Fig. 10 shows the turret
moved over to a central position and the sizing cutter _B_ set for
boring. The head is centrally located (on this particular machine) by a
positive center-stop. The turret is indexed for bringing the different
tools into the working position, by loosening the clamping lever _L_ and
pulling down lever _I_ which disengages the turret lock-pin. When all
the flywheels in a lot have been machined as described, the opposite
side is finished.
[Illustration: Fig. 10. Tool B set for Boring the Hub]
[Illustration: Fig. 11. Diagrams showing Method of Turning and Boring a
Flywheel on a Double-head Mill having one Turret Head]
In order to show more clearly the method of handling work of this class,
the machining of a flywheel will be explained more in detail in
connection with Fig. 11, which illustrates practically the same
equipment as is shown in Figs. 9 and 10. The successive order in which
the various operations are performed is as follows: Tool _a_ (see sketch
_A_) rough turns the side of the rim, while tool _b_, which is set with
its cutting edge toward the rear, rough turns the outside. The direction
of the feeding movement for each tool is indicated by the arrows. When
tool _a_ has crossed the rim, it is moved over for facing the hub, as
shown by the dotted lines. The side and periphery of the rim are next
finished by the broad-nose finishing tools _c_ and _d_ (see sketch _B_).
The feed should be increased for finishing, so that each tool will have
a movement of say 1/4 or 3/8 inch per revolution of the work, and the
cuts should, at least, be deep enough to remove the marks made by the
roughing tools. Tool _c_ is also used for finishing the hub as indicated
by the dotted lines. After these cuts are taken, the outside of the hub
and inner surface of the rim are usually turned down as far as the
spokes, by using offset tools similar to the ones shown at _C_ and _D_
in Fig. 7. The corners of the rim and hub are also rounded to give the
work a more finished appearance, by using a tool _L_.
The next operation is that of finishing the hole through the hub. The
hard scale is first removed by a roughing cutter _r_ (sketch _C_), which
is followed by a "sizing" cutter _s_. The hole is then finished smooth
and to the right diameter by reamer _f_. The bars carrying cutters _r_
and _s_ have extensions or "pilots" which enter a close-fitting bushing
in the table, in order to steady the bar and hold it in alignment.
When the hole is finished, the wheel is turned over, so that the lower
side of the rim and hub can be faced. The method of holding the casting
for the final operation is shown at _D_. The chuck jaws are removed, and
the finished side of the rim is clamped against parallels _p_ resting on
the table. The wheel is centrally located for turning this side by a
plug _e_ which is inserted in a hole in the table and fits the bore of
the hub. The wheel is held by clamps which bear against the spokes.
Roughing and finishing cuts are next taken over the top surface of the
rim and hub and the corners are rounded, which completes the machining
operations. If the rim needs to be a certain width, about the same
amount of metal should be removed from each side, unless sandy spots or
"blow-holes" in the casting make it necessary to take more from one side
than from the other. That side of the rim which was up in the mold when
the casting was made should be turned first, because the porous, spongy
spots usually form on the "cope" or top side of a casting.
=Convex Turning Attachment for Boring Mills.=--Fig. 12 shows a vertical
boring mill arranged for turning pulleys having convex rims; that is,
the rim, instead of being cylindrical, is rounded somewhat so that it
slopes from the center toward either side. (The reason for turning a
pulley rim convex is to prevent the belt from running off at one side,
as it sometimes tends to do when a cylindrical pulley is used.) The
convex surface is produced by a special attachment which causes the
turning tool to gradually move outward as it feeds down, until the
center of the rim is reached, after which the movement is inward.
[Illustration: Fig. 12. Gisholt Mill equipped with Convex Turning
Attachment]
The particular attachment shown in Fig. 12 consists of a special
box-shaped tool-head _F_ containing a sliding holder _G_, in which the
tool is clamped by set-screws passing through elongated slots in the
front of the tool-head. In addition, there is a radius link _L_ which
swivels on a stud at the rear of the tool-head and is attached to
vertical link _H_. Link _L_ is so connected to the sliding tool-block
that any downward movement of the tool-bar _I_ causes the tool to move
outward until the link is in a horizontal position, after which the
movement is reversed. When the attachment is first set up, the turning
tool is placed at the center of the rim and then link _L_ is clamped to
the vertical link while in a horizontal position. The cut is started at
the top edge of the rim, and the tool is fed downward by power, the
same as when turning a cylindrical surface. The amount of curvature or
convexity of a rim can be varied by inserting the clamp bolt _J_ in
different holes in link _L_.
[Illustration: Fig. 13. Turning a Taper or Conical Surface]
The tools for machining the hub and sides of the rim are held in a
turret mounted on the left-hand head, as shown. The special tool-holder
_A_ contains two bent tools for turning the upper and lower edges of the
pulley rim at the same time as the tool-head is fed horizontally.
Roughing and finishing tools _B_ are for facing the hub, and the tools
_C_, _D_, and _E_ rough bore, finish bore, and ream the hole for the
shaft.
=Turning Taper or Conical Surfaces.=--Conical or taper surfaces are
turned in a vertical boring mill by swiveling the tool-bar to the proper
angle as shown in Fig. 13. When the taper is given in degrees, the
tool-bar can be set by graduations on the edge of the circular base _B_,
which show the angle _a_ to which the bar is swiveled from a vertical
position. The base turns on a central stud and is secured to the saddle
_S_ by the bolts shown, which should be tightened after the tool-bar is
set. The vertical power feed can be used for taper turning the same as
for cylindrical work.
[Illustration: Fig. 14. Turning a Conical Surface by using the Combined
Vertical and Horizontal Feeds]
Occasionally it is necessary to machine a conical surface which has such
a large included angle that the tool-bar cannot be swiveled far enough
around to permit turning by the method illustrated in Fig. 13. Another
method, which is sometimes resorted to for work of this class, is to use
the combined vertical and horizontal feeds. Suppose we want to turn the
conical casting _W_ (Fig. 14), to an angle of 30 degrees, as shown, and
that the tool-head of the boring mill moves horizontally 1/4 inch per
turn of the feed-screw and has a vertical movement of 3/16 inch per turn
of the upper feed-shaft. If the two feeds are used simultaneously, the
tool will move a distance _h_ of say 8 inches, while it moves downward a
distance _v_ of 6 inches, thus turning the surface to an angle _y_. This
angle is greater (as measured from a horizontal plane) than the angle
required, but, if the tool-bar is swiveled to an angle _x_, the tool, as
it moves downward, will also be advanced horizontally, in addition to
the regular horizontal movement. The result is that the angle _y_ is
diminished and if the tool-bar is set over the right amount, the
conical surface can be turned to an angle _a_ of 30 degrees. The
problem, then, is to determine what the angle _x_ should be for turning
to a given angle _a_.
[Illustration: Fig. 15. Diagram showing Method of Obtaining Angular
Position of Tool-head when Turning Conical Surfaces by using Vertical
and Horizontal Feeding Movements]
The way angle _x_ is calculated will be explained in connection with the
enlarged diagram, Fig. 15, which shows one-half of the casting. The sine
of the known angle _a_ is first found in a table of natural sines. Then
the sine of angle _b_, between the taper surface and center-line of the
tool-head, is determined as follows: sin_b_ = (sin_a_ x _h_) / _v_, in
which _h_ represents the rate of horizontal feed and _v_ the rate of
vertical feed. The angle corresponding to sine _b_ is next found in a
table of sines. We now have angles _b_ and _a_, and by subtracting the
sum of these angles from 90 degrees, the desired angle _x_ is obtained.
To illustrate: The sine of 30 degrees is 0.5; then sin _b_ = (0.5 x 1/4)
/ 3/16 = 0.6666; hence angle _b_ = 41 degrees 49 minutes, and _x_ =
90 deg.-(30 deg. + 41 deg. 49') = 18 degrees 11 minutes. Hence to turn
the casting to angle _a_ in a boring mill having the horizontal and
vertical feeds given, the tool-head would be set over from the vertical
18 degrees and 11 minutes which is equivalent to about 18-1/6 degrees.
If the required angle _a_ were greater than angle _y_ obtained from the
combined feeds with the tool-bar in a vertical position, it would then
be necessary to swing the lower end of the bar to the left rather than
to the right of a vertical plane. When the required angle _a_ exceeds
angle _y_, the sum of angles _a_ and _b_ is greater than 90 degrees so
that angle _x_ for the tool-head = (_a_ + _b_) - 90 degrees.
=Turret-lathe Type of Vertical Boring Mill.=--The machine illustrated in
Fig. 16 was designed to combine the advantages of the horizontal turret
lathe and the vertical boring mill. It is known as a "vertical turret
lathe," but resembles, in many respects, a vertical boring mill. This
machine has a turret on the cross-rail the same as many vertical boring
mills, and, in addition, a side-head _S_. The side-head has a vertical
feeding movement, and the tool-bar _T_ can be fed horizontally. The
tool-bar is also equipped with a four-sided turret for holding turning
tools. This arrangement of the tool-heads makes it possible to use two
tools simultaneously upon comparatively small work. When both heads are
mounted on the cross-rail, as with a double-head boring mill, it is
often impossible to machine certain parts to advantage, because one head
interferes with the other.
The drive to the table (for the particular machine illustrated) is from
a belt pulley at the rear, and fifteen speed changes are available. Five
changes are obtained by turning the pilot-wheel _A_ and this series of
five speeds is compounded three times by turning lever _B_. Each spoke
of pilot-wheel _A_ indicates a speed which is engaged only when the
spoke is in a vertical position, and the three positions for _B_ are
indicated, by slots in the disk shown. The number of table revolutions
per minute for different positions of pilot-wheel _A_ and lever _B_ are
shown by figures seen through whichever slot is at _C_. There are five
rows of figures corresponding to the five spokes of the pilot-wheel and
three figures in a row, and the speed is shown by arrows on the sides of
the slots. The segment disk containing these figures also serves as an
interlocking device which prevents moving more than one speed
controlling lever at a time, in order to avoid damaging the driving
mechanism.
[Illustration: Fig. 16. Bullard Vertical Turret Lathe]
The feeding movement for each head is independent. Lever _D_ controls
the engagement or disengagement of the vertical or cross feeds for the
head on the cross-rail. The feed for the side-head is controlled by
lever _E_. When this lever is pushed inward, the entire head feeds
vertically, but when it is pulled out, the tool-bar feeds horizontally.
These two feeds can be disengaged by placing the lever in a neutral
position. The direction of the feeding movement for either head can be
reversed by lever _R_. The amount of feed is varied by feed-wheel _F_
and clutch-rod _G_. When lever _E_ is in the neutral position, the
side-head or tool-bar can be adjusted by the hand-cranks _H_ and _I_,
respectively. The cross-rail head and its turret slide have rapid power
traverse movements for making quick adjustments. This rapid traverse is
controlled by the key-handles _J_.
The feed-screws for the vertical head have micrometer dials _K_ for
making accurate adjustments. There are also large dials at _L_ which
indicate vertical movements of the side head and horizontal movements of
the tool slide. All of these dials have small adjustable clips _c_ which
are numbered to correspond to numbers on the faces of the respective
turrets. These clips or "observation stops" are used in the production
of duplicate parts. For example, suppose a tool in face No. 1 for the
main turret is set for a given diameter and height of shoulder on a part
which is to be duplicated. To obtain the same setting of the tools for
the next piece, clips No. 1, on both the vertical feed rod and screw
dials, are placed opposite the graduations which are intersected by
stationary pointers secured to the cross-rail. The clips are set in this
way after the first part has been machined to the required size and
before disturbing the final position of the tools. For turning a
duplicate part, the tools are simply brought to the same position by
turning the feed screws until the clips and stationary pointers again
coincide. For setting tools on other faces of either turret, this
operation is repeated, except that clips are used bearing numbers
corresponding to the turret face in use.
The main turret of this machine has five holes in which are inserted the
necessary boring and turning tools, drills or reamers, as may be
required. By having all the tools mounted in the turret, they can be
quickly and accurately set in the working position. When the turret is
indexed from one face to the next, binder lever _N_ is first loosened.
The turret then moves forward, away from its seat, thus disengaging the
indexing and registering pins which accurately locate it in any one of
the five positions. The turret is revolved by turning crank _M_, one
turn of this handle moving the turret 1/5 revolution or from one hole to
the next. The side-head turret is turned by loosening lever _O_. The
turret slide can be locked rigidly in any position by lever _P_ and its
saddle is clamped to the cross-rail by lever _Q_. The binder levers for
the saddle and toolslide of the side-head are located at _U_ and _V_,
respectively. A slide that does not require feeding movements is locked
in order to obtain greater rigidity. To illustrate, if the main tool
slide were to feed vertically and not horizontally, it might be
advisable to lock the saddle to the cross-rail, while taking the
vertical cut.
[Illustration: Fig. 17. Turning a Gear Blank on a Vertical Turret Lathe]
The vertical slide can be set at an angle for taper turning, and the
turret is accurately located over the center of the table for boring or
reaming, by a positive center stop. The machine is provided with a brake
for stopping the work table quickly, which is operated by lifting the
shaft of pilot-wheel _A_. The side-and cross-rails are a unit and are
adjusted together to accommodate work of different heights. This
adjustment is effected by power on the particular machine illustrated,
and it is controlled by a lever near the left end of the cross-rail.
Before making this adjustment, all binder bolts which normally hold the
rails rigidly to the machine column must be released, and care should be
taken to tighten them after the adjustment is made.
[Illustration: Fig. 18. Turning Gasoline Engine Flywheel on Vertical
Turret Lathe--First Position]
=Examples of Vertical Turret Lathe Work.=--In order to illustrate how a
vertical turret lathe is used, one or two examples of work will be
referred to in detail. These examples also indicate, in a general way,
the class of work for which this type of machine is adapted. Fig. 17
shows how a cast-iron gear blank is machined. The work is gripped on the
inside of the rim by three chuck jaws, and all of the tools required for
the various operations are mounted in the main and side turrets. The
illustration shows the first operation which is that of rough turning
the hub, the top side of the blank and its periphery. The tools _A_ for
facing the hub and upper surface are both held in one tool-block on the
main turret, and tool _A_{1}_ for roughing the periphery is in the side
turret. With this arrangement, the three surfaces can be turned
simultaneously.
[Illustration: Fig. 19. Turning Gasoline Engine Flywheel--Second
Position]
[Illustration: Fig. 20. Diagrams showing How Successive Operations are
Performed by Different Tools in the Turret]
The main turret is next indexed one-sixth of a revolution which brings
the broad finishing tools _B_ into position, and the side turret is also
turned to locate finishing tool _B_{1}_ at the front. (The indexing of
the main turret on this particular machine is effected by loosening
binder lever n and raising the turret lock-pin by means of lever _p_.)
The hub, side and periphery of the blank are then finished. When tools
_B_ are clamped in the tool-blocks, they are, of course, set for
turning the hub to the required height. The third operation is performed
by the tools at _C_, one of which "breaks" or chamfers the corner of the
cored hole in the hub, to provide a starting surface for drill _D_, and
the other turns the outside of the hub, after the chamfering tool is
removed. The four-lipped shell-drill _D_ is next used to drill the cored
hole and then this hole is bored close to the finished size and
concentric with the circumference of the blank by boring tool _E_, which
is followed by the finishing reamer _F_. When the drill, boring tool and
reamer are being used, the turret is set over the center or axis of the
table, by means of a positive center stop on the left-side of the turret
saddle. If it is necessary to move the turret beyond the central
position, this stop can be swung out of the way.
Figs. 18 and 19 illustrate the turning of an automobile flywheel, which
is another typical example of work for a machine of this type. The
flywheel is finished in two settings. Its position for the first series
of operations is shown in Fig. 18, and the successive order of the four
operations for the first setting is shown by the diagrams, Fig. 20. The
first operation requires four tools which act simultaneously. The three
held in tool-block _A_ of the turret, face the hub, the web and the rim
of the flywheel, while tool _a_ in the side-head rough turns the outside
diameter. The outside diameter is also finished by broad-nosed tool _b_
which is given a coarse feed. In the second operation, the under face of
the rim is finished by tool _c_, the outer corners are rounded by tool
_d_ and the inner surface of the rim is rough turned by a bent tool _B_,
which is moved into position by indexing the main turret. In the third
operation, the side-head is moved out of the way and the inside of the
rim is finished by another bent tool _B_{1}_. The final operation at
this setting is the boring of the central hole, which is done with a bar
_C_ having interchangeable cutters which make it possible to finish the
hole at one setting of the turret.
The remaining operations are performed on the opposite side of the work
which is held in "soft" jaws _J_ accurately bored to fit the finished
outside diameter as indicated in Fig. 19. The tool in the main turret
turns the inside of the rim, and the side-head is equipped with two
tools for facing the web and hub simultaneously. As the tool in the main
turret operates on the left side of the rim, it is set with the cutting
edge toward the rear. In order to move the turret to this position,
which is beyond the center of the table, the center stop previously
referred to is swung out of the way.
=Floating Reamer Holders.=--If a reamer is held rigidly in the turret of
a boring mill or turret lathe, it is liable to produce a hole which
tapers slightly or is too large. When a hole is bored with a
single-point boring tool, it is concentric with the axis of rotation,
and if a reamer that is aligned exactly with the bored hole is fed into
the work, the finished hole should be cylindrical and the correct size.
It is very difficult, however, to locate a reamer exactly in line with a
bored hole, because of slight variations in the indexing of the turret,
or errors resulting from wear of the guiding ways or other important
parts of the machine.
To prevent inaccuracies due to this cause, reamers are often held in
what is known as a "floating" holder. This type of holder is so arranged
that the reamer, instead of being held rigidly, is allowed a slight free
or floating movement so that it can follow a hole which has been bored
true, without restraint. In this way the hole is reamed straight and to
practically the same size as the reamer.
[Illustration: Fig. 21. Two Types of Floating Reamer Holders]
There are many different designs of floating holders but the general
principle upon which they are based is illustrated by the two types
shown in Fig. 21. The reamer and holder shown to the left has a
ball-shank _A_ which bears against a backing-up screw _B_ inserted in
the end of holder _C_ through which the driving pin passes. The lower
end of the reamer shank is also spherical-shaped at _D_, and screw-pin
_E_ secures the shell reamer to this end. It will be noted that the hole
in the shank for pin _E_ is "bell-mouthed" on each side of the center
and that there is clearance at _F_ between the shank and reamer shell;
hence the reamer has a free floating action in any direction. This
holder has given very satisfactory results.
[Illustration: Fig. 22. Multiple-spindle Cylinder Boring Machine]
The holder shown to the right is attached to the face of the turret by
four fillister-head screws. Sleeve _C_ is held in plate _A_ by means of
two steel pins _B_ which are tight in plate _A_ and made to fit freely
in bayonet grooves _D_. Reamer holder _E_ floats on sleeve _C_, the
floating motion being obtained through the four steel pins _G_ extending
into driving ring _F_. Two of the pins are tight in the holder _E_ and
two in sleeve _C_. The faces of sleeve _C_, driving ring _F_, and reamer
holder _E_ are held tightly against each other by means of spring _H_
which insures the reamer being held perfectly true. Spring _H_ is
adjusted by means of nut _I_ which is turned with a spanner wrench
furnished with each holder. The reamer is so held that its axis is
always maintained parallel to the center of the hole, and, at the same
time, it has a slight self-adjusting tendency radially, so that the hole
and reamer will automatically keep in perfect alignment with each
other.
=Multiple Cylinder Boring Machine.=--In automobile and other factories
where a great many gasoline engine cylinders are required,
multiple-spindle boring machines of the vertical type are commonly used.
The machine shown in Fig. 22 is a special design for boring four
cylinders which are cast _en bloc_ or in one solid casting. The work is
held in a box jig which has a top plate equipped with guide bearings for
holding the spindles rigidly while boring. The lower end of each spindle
has attached to it a cutter-head and the boring is done by feeding the
table and casting vertically. This feeding movement is effected by power
and it is disengaged automatically when the cutters have bored to the
required depth. The particular machine illustrated is used for rough
boring only, the cylinders being finished by reaming in another similar
machine. The cylinders are bored to a diameter of 3-5/8 inches, and
about 3/8 inch of metal is removed by the roughing cut. The spindles
have fixed center-to-center distances as the machine is intended for
constant use on cylinders of one size, so that adjustment is not
necessary. Of course, a special machine of this kind is only used in
shops where large numbers of cylinders of one design are required
continually. Some cylinder boring machines of the vertical type have
spindles which can be adjusted for different center-to-center distances
if this should be necessary in order to accommodate a cylinder of
another size.
CHAPTER VII
HORIZONTAL BORING MACHINES
A boring machine of the horizontal type is shown in Fig. 1. The
construction and operation of this machine is very different from that
of a vertical boring mill and it is also used for an entirely different
class of work. The horizontal machine is employed principally for
boring, drilling or milling, whereas the vertical design is especially
adapted to turning and boring. The horizontal type is also used for
turning or facing flanges or similar surfaces when such an operation can
be performed to advantage in connection with other machine work on the
same part.
The type of machine illustrated in Fig. 1 has a heavy base or bed to
which is bolted the column _C_ having vertical ways on which the
spindle-head _H_ is mounted. This head contains a sleeve or quill in
which the spindle _S_ slides longitudinally. The spindle carries cutters
for boring, whereas milling cutters or the auxiliary facing arm are
bolted to the end _A_ of the spindle sleeve. The work itself is attached
either directly or indirectly to the table or platen _P_. When the
machine is in operation, the cutter or tool revolves with the spindle
sleeve or spindle and either the cutter or the part being machined is
given a feeding movement, depending on the character of the work. The
spindle can be moved in or out by hand for adjustment, or by power for
feeding the cutter, as when boring or drilling.
[Illustration: Fig. 1. Lucas Horizontal Boring, Drilling and Milling
Machine]
The entire spindle-head _H_ can also be moved vertically on the face of
the column _C_, by hand, for setting the spindle to the proper height,
or by power for feeding a milling cutter in a vertical direction. When
the vertical position of the spindle-head is changed, the outboard
bearing block _B_ also moves up or down a corresponding amount, the two
parts being connected by shafts and gearing. Block _B_ steadies the
outer end of the boring-bar and the back-rest in which this block is
mounted can be shifted along the bed to suit the length of the work, by
turning the squared end of shaft _D_ with a crank. The platen _P_ has a
cross-feed, and the saddle _E_ on which it is mounted can be traversed
lengthwise on the bed; both of these movements can also be effected by
hand or power. There is a series of power feeding movements for the
cutters and, in addition, rapid power movements _in a reverse direction
from the feed_ for returning a cutter quickly to its starting position,
when this is desirable.
This machine is driven by a belt connecting pulley _G_ with an overhead
shaft. When the machine is in operation, this pulley is engaged with the
main driving shaft by a friction clutch _F_ controlled by lever _L_.
This main shaft drives through gearing a vertical shaft _I_, which by
means of other gears in the spindle-head imparts a rotary movement to
the spindle. As a machine of this type is used for boring holes of
various diameters and for a variety of other work, it is necessary to
have a number of speed changes for the spindle. Nine speeds are obtained
by changing the position of the sliding gears controlled by levers _R_
and this number is doubled by back-gears in the spindle-head and
controlled by lever _J_.
The amount of feed for the spindle, spindle-head, platen or saddle is
varied by two levers _K_ and _K_{1}_ which control the position of
sliding gears through which the feeding movements are transmitted. The
direction of the feed can be reversed by shifting lever _O_. With this
particular machine, nine feed changes are available for each position of
the spindle back-gears, making a total of eighteen changes. The feeding
movement is transmitted to the spindle-head, spindle, platen or saddle,
as required, by the three distributing levers _T_, _U_ and _V_, which
control clutches connecting with the transmission shafts or feed screws.
When lever _T_ is turned to the left, the longitudinal power feed for
the spindle is engaged, whereas turning it to the right throws in the
vertical feed for the spindle-head. Lever _U_ engages the cross-feed for
platen _P_ and lever _V_, the longitudinal feed for saddle _E_. These
levers have a simple but ingenious interlocking device which makes it
impossible to engage more than one feed at a time. For example, if lever
_T_ is set for feeding the spindle, levers _U_ and _V_ are locked
against movement.
The feeds are started and stopped by lever _M_ which also engages the
rapid power traverse when thrown in the opposite direction. This rapid
traverse operates for whatever feed is engaged by the distributing
levers and, as before stated, in a reverse direction. For example, if
the reverse lever _O_ is set for feeding the spindle to the right, the
rapid traverse would be to the left, and _vice versa_. The cross-feed
for the platen can be automatically tripped at any point by setting an
adjustable stop in the proper position and the feed can also be tripped
by a hand lever at the side of the platen.
All the different feeding movements can be effected by hand as well as
by power. By means of handwheel _N_, the spindle can be moved in or out
slowly, for feeding a cutter by hand. When the friction clamp _Q_ is
loosened, the turnstile _W_ can be used for traversing the spindle, in
case a hand adjustment is desirable. The spindle-head can be adjusted
vertically by turning squared shaft _X_ with a crank, and the saddle can
be shifted along the bed by turning shaft _Y_. The hand adjustment of
the platen is effected by shaft _Z_. The spindle-head, platen and saddle
can also be adjusted from the end of the machine, when this is more
convenient. Shafts _X_, _Y_ and _Z_ are equipped with micrometer dials
which are graduated to show movements of one-thousandth inch. These
dials are used for accurately adjusting the spindle or work and for
boring holes or milling surfaces that must be an exact distance apart.
=Horizontal Boring Machine with Vertical Table Adjustment.=--Another
horizontal boring machine is partly shown in Fig. 2. This machine is of
the same type as that illustrated in Fig. 1, but its construction is
quite different, as will be seen. The spindle cannot be adjusted
vertically as with the first design described, but it is mounted and
driven very much like the spindle of a lathe, and adjustment for height
is obtained by raising or lowering the work table. The design is just
the reverse, in this respect, of the machine shown in Fig. 1, which has
a vertical adjustment for the spindle, and a work table that remains in
the same horizontal plane. The raising or lowering of the table is
effected by shaft _E_, which rotates large nuts engaging the screws _S_.
Shaft _E_ is turned either by hand or power.
[Illustration: Fig. 2. Horizontal Boring and Drilling Machine with
Vertical Table Adjustment]
The main spindle is driven by a cone pulley _P_, either directly, or
indirectly through the back-gears shown. This arrangement gives six
spindle speeds, and double this number is obtained by using a two-speed
countershaft overhead. The motion for feeding the spindle longitudinally
is transmitted through a cone of gears, which gives the required
changes, to a pinion meshing with a rack which traverses the spindle.
The large handwheel _H_ and a corresponding wheel on the opposite side
are used for adjusting the spindle rapidly by hand. The yoke or outboard
bearing _B_ for the boring-bars can be clamped in any position along the
bed for supporting the bar as close to the work as possible.
Horizontal boring machines are built in many other designs, but they all
have the same general arrangement as the machines illustrated and
operate on the same principle, with the exception of special types
intended for handling certain classes of work exclusively. The
horizontal boring, drilling and milling machine is very efficient for
certain classes of work because it enables all the machining operations
on some parts to be completed at one setting. To illustrate, a casting
which requires drilling, boring and milling at different places, can
often be finished without disturbing its position on the platen after it
is clamped in place. Frequently a comparatively small surface needs to
be milled after a part has been bored. If this milling operation can be
performed while the work is set up for boring, accurate results will be
obtained (provided the machine is in good condition) and the time saved
that would otherwise be required for re-setting the part on another
machine. Some examples of work on which different operations are
performed at the same setting will be referred to later. The horizontal
boring machine also makes it possible to machine duplicate parts without
the use of jigs, which is important, especially on large work, owing to
the cost of jigs.
=Drilling and Boring--Cutters Used.=--Holes are drilled in a horizontal
machine by simply inserting a drill of required size either directly in
the spindle _S_ (see Fig. 1), or in a reducing socket, and then feeding
the spindle outward either by hand or power. When a hole is to be bored,
a boring-bar _B_{1}_ is inserted in the spindle and the cutter is
attached to this bar. The latter is then fed through the hole as the
cutter revolves. The distinction made by machinists between drilling and
boring is as follows: A hole is said to be drilled when it is formed by
sinking a drill into solid metal, whereas boring means the enlargement
of a drilled or cored hole either by the use of a single boring tool, a
double-ended cutter which operates on both sides of the hole, or a
cutter-head having several tools.
There are various methods of attaching cutters to boring-bars and the
cutters used vary for different classes of work. A simple style of
cutter which is used widely for boring small holes is shown at _A_ in
Fig. 3. The cutter _c_ is made from flat stock and the cutting is done
by the front edges _e_ and _e_{1}_, which are beveled in opposite
directions. The cutter is held in the bar by a taper wedge _w_ and it
is centered by shoulders at _s_, so that the diameter of the hole will
equal the length across the cutter. The outer corners at the front
should be slightly rounded, as a sharp corner would be dulled quickly.
These cutters are made in different sizes and also in sets for roughing
and finishing. The roughing cutter bores holes to within about 1/32 inch
of the finish size and it is then replaced by the finishing cutter. A
cutter having rounded ends, as shown by the detail sketch _a_, is
sometimes used for light finishing cuts. These rounded ends form the
cutting edges and give a smooth finish.
[Illustration: Fig. 3. Boring-cutters of Different Types]
Another method of holding a flat cutter is shown at _B_. The conical end
of a screw bears against a conical seat in, the cutter, thus binding the
latter in its slot. The conical seat also centers the cutter. A very
simple and inexpensive form of cutter is shown at _C_. This is made from
a piece of round steel, and it is held in the bar by a taper pin which
bears against a circular recess in the side of the cutter. This form
has the advantage of only requiring a hole through the boring-bar,
whereas it is necessary to cut a rectangular slot for the flat cutter.
[Illustration: Fig. 4. Boring with a Flat Double-ended Cutter]
Fig. 4 shows how a hole is bored by cutters of the type referred to. The
bar rotates as indicated by the arrow _a_ and at the same time feeds
longitudinally as shown by arrow _b_. The speed of rotation depends upon
the diameter of the hole and the kind of material being bored, and the
feed per revolution must also be varied to suit conditions. No definite
rule can be given for speed or feed. On some classes of work a long
boring-bar is used, which passes through the hole to be bored and is
steadied at its outer end by the back-rest _B_, Figs, 1 and 2. On other
work, a short bar is inserted in the spindle having a cutter at the
outer end. An inexpensive method of holding a cutter at the end of a bar
is shown at _D_, Fig. 3. The cutter passes through a slot and is clamped
by a bolt as shown. When it is necessary to bore holes that are "blind"
or closed at the bottom, a long boring-bar which passes through the work
cannot, of course, be used.
Sometimes it is necessary to have a cutter mounted at the extreme end of
a bar in order to bore close to a shoulder or the bottom of a hole. One
method of holding a cutter so that it projects beyond the end of a bar
is indicated at _E_. A screw similar to the one shown at _B_ is used,
and the conical end bears in a conical hole in the cutter. This hole
should be slightly offset so that the cutter will be forced back
against its seat. The tool shown at _F_ has adjustable cutters. The
inner end of each cutter is tapering and bears against a conical-headed
screw _b_ which gives the required outward adjustment. The cutters are
held against the central bolt by fillister-head screws _f_ and they are
clamped by the screws _c_. Boring tools are made in many different
designs and the number and form of the cutters is varied somewhat for
different kinds of work.
[Illustration: Fig. 5. Cutter-heads for Boring Large Holes]
=Cutter-heads for Boring Large Holes.=--When large holes are to be
bored, the cutters are usually held in a cast-iron head which is mounted
on the boring-bar. One type of cutter-head is shown in Fig. 5. This
particular head is double-ended and carries two cutters _c_. The
cutter-head is bored to fit the bar closely and it is prevented from
turning by a key against which a set-screw is tightened. By referring to
the end view, it will be seen that each cutter is offset with relation
to the center of the bar, in order to locate the front of the tool on a
radial line. The number of cutters used in a cutter-head varies. By
having several cutters, the work of removing a given amount of metal in
boring is distributed, and holes can be bored more quickly with a
multiple cutter-head, although more power is required to drive the
boring-bar. The boring-bar is also steadied by a multiple cutter-head,
because the tendency of any one cutter to deflect the bar is
counteracted by the cutters on the opposite side.
A disk-shaped head having four cutters is illustrated in Fig. 6. The
cutters are inserted in slots or grooves in the face of the disk and
they are held by slotted clamping posts. The shape of these posts is
shown by the sectional view. The tool passes through an elongated slot
and it is tightly clamped against the disk by tightening nut _n_. This
head is also driven by a key which engages a keyway in the boring-bar.
[Illustration: Fig. 6. Cutter-head with Four Boring Tools]
Two other designs of cutter-heads are shown in Fig. 7. The one
illustrated at _A_ has three equally spaced cutters which are held in an
inclined position. The cutters are clamped by screws _c_ and they can be
adjusted within certain limits by screws _s_. The cutters are placed at
an angle so that they will extend beyond the front of the head, thus
permitting the latter to be moved up close to a shoulder. The
cutter-heads shown in Figs. 5 and 6 can also be moved up close to a
shoulder if bent cutters are used as shown in the right-hand view, Fig.
5. The idea in bending the cutters is to bring the cutting edges in
advance of the clamping posts so that they will reach a shoulder before
the binding posts strike it. The arrangement of cutter-head _B_ (Fig. 7)
is clearly shown by the illustration.
Cutter-heads are often provided with two sets of cutters, one set being
used for roughing and the other for finishing. It is a good plan to make
these cutters so that the ends _e_ (Fig. 6) will rest against the bar or
bottom of the slot, when the cutting edge is set to the required radius.
The cutters can then be easily set for boring duplicate work. One method
of making cutters in sets is to clamp the annealed stock in the
cutter-head and then turn the ends to the required radius by placing the
head in the lathe. After both sets of cutters have been turned in this
way, they are ground to shape and then hardened.
[Illustration: Fig. 7. Cutter-heads equipped with Adjustable Tools]
Boring cutters intended for roughing and finishing cuts are shown in the
detail view Fig. 8 at _A_ and _B_, respectively. The side of the
roughing cutter _A_ is ground to a slight angle _c_ to provide clearance
for the cutting edge, and the front has a backward slope _s_ to give the
tool keenness. This tool is a good form to use for roughing cuts in cast
iron. The finishing tool at _B_ has a broad flat edge _e_ and it is
intended for coarse feeds and light cuts in cast iron. If a round
cutting edge is used for finishing, a comparatively fine feed is
required in order to obtain a smooth surface. The corners of tool _B_
are rounded and they should be ground to slope inward as shown in the
plan view. The top or ends _d_ of both of these tools are "backed off"
slightly to provide clearance. This clearance should be just enough to
prevent the surface back of the cutting edge from dragging over the
work. Excessive end clearance not only weakens the cutting edge, but
tends to cause chattering. As a finishing tool cuts on the upper end
instead of on the side, the front should slope backward as shown in the
side view, rather than sidewise as with a roughing cutter. The angle of
the slope should be somewhat greater for steel than cast iron, unless
the steel is quite hard, thus requiring a strong blunt tool.
[Illustration: Fig. 8. Boring Tools for Roughing and Finishing Cuts]
=Cylinder Boring.=--Fig. 9 illustrates the use of a cutter-head for
cylinder boring. After the cylinder casting is set on the platen of the
machine, the boring-bar with the cutter-head mounted on it is inserted
in the spindle. The bar _B_ has a taper shank and a driving tang similar
to a drill shank, which fits a taper hole in the end of the spindle. The
cutter-head _C_ is fastened to the bar so that it will be in the
position shown when the spindle is shifted to the right, as the feeding
movement (with this particular machine) is to be in the opposite
direction. The casting _A_ should be set central with the bar by
adjusting the work-table vertically and laterally, if necessary, and the
outer support _F_ should be moved close to the work, to make the bar as
rigid as possible.
The cylinder is now ready to be bored. Ordinarily, one or two roughing
cuts and one finishing cut would be sufficient, unless the rough bore
were considerably below the finish diameter. As previously explained,
the speed and feed must be governed by the kind of material being bored
and the diameter of the cut. The power and rigidity of the boring
machine and the quality of the steel used for making the cutters also
affect the cutting speed and feed. As the finishing cut is very light, a
tool having a flat cutting edge set parallel to the bar is ordinarily
used when boring cast iron. The coarse feed enables the cut to be taken
in a comparatively short time and the broad-nosed tool gives a smooth
finish if properly ground.
[Illustration: Fig. 9. Cylinder mounted on Horizontal Machine for
Boring]
The coarse finishing feed is not always practicable, especially if the
boring machine is in poor condition, owing to the chattering of the
tool, which results in a rough surface. The last or finishing cut should
invariably be a continuous one, for if the machine is stopped before the
cut is completed, there will be a ridge in the bore at the point where
the tool temporarily left off cutting. This ridge is caused by the
cooling and resulting contraction and shortening of the tool during the
time that it is stationary. For this reason independent drives are
desirable for boring machines.
Facing arms are attached to the bar on either side of the cylinder for
facing the flanges after the boring operation. The turning tool of a
facing arm is fastened to a slide which is fed outward a short distance
each revolution, by a star-wheel that is caused to turn as it strikes
against a stationary pin. By facing the flanges in this way, they are
finished square with the bore.
When setting a cylinder which is to be bored it should, when the design
will permit, be set true by the outside of the flange, or what is even
better, by the outside of the cylinder itself, rather than by the rough
bore, in order that the walls of the finished cylinder will have a
uniform thickness. The position of very large cylinders, while they are
being bored, is an important consideration. Such cylinders should be
bored in the position which they will subsequently occupy when
assembled. For example, the cylinder for a large horizontal engine
should be bored while in a horizontal position, as the bore is liable to
spring to a slight oval shape when the cylinder is placed horizontal
after being bored while standing in a vertical position. If, however,
the cylinder is bored while in the position in which it will be placed
in the assembled engine, this trouble is practically eliminated.
There is a difference of opinion among machinists as to the proper shape
of the cutting point of a boring tool for finishing cuts, some
contending that a wide cutting edge is to be preferred, while others
advocate the use of a comparatively narrow edge with a reduced feed. It
is claimed, that the narrow tool produces a more perfect bore, as it is
not so easily affected by hard spots in the iron, and it is also pointed
out that the minute ridges left by the narrow tool are an advantage
rather than a disadvantage, as they form pockets for oil and aid in
lubricating the cylinder. It is the modern practice, however, to use a
broad tool and a coarse feed for the light finishing cut, provided the
tool does not chatter.
The type of machine tool used for boring cylinders, and also the method
of procedure is determined largely by the size of the work and the
quantity which is to be machined. The turret lathe, as well as
horizontal and vertical boring mills, is used for this work, and in
automobile factories or other shops where a great many cylinders are
bored, special machines and fixtures are often employed.
[Illustration: Fig. 10. Boring a Duplex Cylinder on a Horizontal
Machine]
=Boring a Duplex Gasoline Engine Cylinder.=--The method of holding work
on a horizontal boring machine depends on its shape. A cylinder or other
casting having a flat base can be clamped directly to the platen, but
pieces of irregular shape are usually held in special fixtures. Fig. 10
shows how the cylinder casting of a gasoline engine is set up for the
boring operation. The casting _W_ is placed in a fixture _F_ which is
clamped to the machine table. One end of the casting rests on the
adjustable screws _S_ and it is clamped by set-screws located in the top
and sides of the fixture. There are two cylinders cast integral and
these are bored by a short stiff bar mounted in the end of the spindle
and having cutters at the outer end. A long bar of the type which passes
through the work and is supported by the outboard bearing _B_, could not
be used for this work, because the top of each cylinder is closed.
When one cylinder is finished the other is set in line with the spindle
by adjusting the work-table laterally. This adjustment is effected by
screw _C_, and the required center-to-center distance between the two
cylinders can be gaged by the micrometer dial _M_ on the cross-feed
screw, although positive stops are often used in preference. After the
first cylinder is bored, the dial is set to the zero position by
loosening the small knurled screw shown, and turning the dial around.
The feed screw is then rotated until the dial shows that the required
lateral adjustment is made, which locates the casting for boring the
second cylinder. The end of the casting is also faced true by a milling
cutter. Ordinarily, milling cutters are bolted directly to the spindle
sleeve _A_ on this particular machine, which gives a rigid support for
the cutter and a powerful drive.
[Illustration: Fig. 11. Cylinder turned around for Machining Valve
Seats]
The next operation is that of boring and milling the opposite end of the
cylinder. This end is turned toward the spindle (as shown in Fig. 11)
without unclamping the work or fixture, by simply turning the circular
table _T_ half way around. This table is an attachment which is clamped
to the main table for holding work that must be turned to different
positions for machining the various parts. Its position is easily
changed, and as the work remains fixed with relation to the table, the
alignment between different holes or surfaces is assured, if the table
is turned the right amount. In this case, the casting needs to be
rotated one-half a revolution or 180 degrees, and this is done by means
of angular graduations on the base of the table. The illustration shows
the casting set for boring the inlet and exhaust valve chambers. The
different cutters required for boring are mounted on one bar as shown,
and the casting is adjusted crosswise to bring each valve chamber in
position, by using the micrometer dial. The single-ended cutter _c_
forms a shallow circular recess or seat in the raised pad which
surrounds the opening. The cover joint directly back of the cylinders is
finished by milling.
[Illustration: Fig. 12. Boring Differential Gear Casing]
=Examples of Boring, Radial Facing and Milling.=--Another example of
boring, in which the circular table is used, is shown in Fig. 12. The
work _W_ is a casing for the differential gears of an automobile. It is
mounted in a fixture _F_ which is bolted to the table. The casting has
round ends, which are clamped in V-blocks, thus aligning the work. This
fixture has a guide-bushing _G_ which is centered with the bar and
cutter in order to properly locate the casting. There is a bearing at
each end of the casing, and two larger ones in the center. These are
bored by flat cutters similar to the style illustrated at _A_ in Fig. 3.
The cutter for the inner bearings is shown at _c_.
[Illustration: Fig. 13. Facing and Turning Flange of Differential Gear
Casing]
After the bearings are bored, the circular table is turned 90 degrees
and the work is moved closer to the spindle (as shown in Fig. 13) for
facing flange _F_ at right angles to the bearings. Circular flanges of
this kind are faced in a horizontal boring machine by a special
facing-arm or head _H_. For this particular job this head is clamped
directly to the spindle sleeve, but it can also be clamped to the
spindle if necessary. The turning tool is held in a slotted toolpost,
and it is fed radially for turning the side or face of the flange, by
the well-known star feed at _S_. When this feed is in operation the bent
finger _E_ is turned downward so that it strikes one of the star wheel
arms for each revolution; this turns the wheel slightly, and the
movement is transmitted to the tool-block by a feed-screw. The
illustration shows the tool set for turning the outside or periphery of
the flange. This is done by setting the tool to the proper radius and
then feeding the work horizontally by shifting the work-table along the
bed. By referring to Fig. 12 it will be seen that the facing head does
not need to be removed for boring, as it is attached to the spindle
driving quill and does not interfere with the longitudinal adjustment of
the spindle. This facing head is also used frequently for truing the
flanges of cylinders which are to be bored, and for similar work.
[Illustration: Fig. 14. Example of Work requiring Boring and Milling]
Fig. 14 shows another example of work which requires boring and milling.
This casting is mounted on a fixture which is bolted to the main table.
In this case the circular table is not necessary, because the work can
be finished without swiveling it around. After the boring is completed
the edge _E_ is trued by the large-face milling cutter _M_ bolted to the
spindle sleeve. The irregular outline of the edge is followed by moving
the table crosswise and the spindle vertically, as required.
=Fixture for Cylinder Lining or Bushing.=--A method of holding a
cylinder lining or bushing while it is being bored is shown in Fig. 15.
The lining _L_ is mounted in two cast-iron ring-shaped fixtures _F_.
These fixtures are circular in shape and have flat bases which are
bolted to the table of the machine. On the inside of each fixture, there
are four equally spaced wedges _W_ which fit into grooves as shown in
the end view. These wedges are drawn in against the work by bolts, and
they prevent the lining from rotating when a cut is being taken. This
form of fixture is especially adapted for holding thin bronze linings,
such as are used in pump cylinders, because only a light pressure
against the wedges is required, and thin work can be held without
distorting it. If a very thin lining is being bored, it is well to
loosen the wedges slightly before taking the finishing cut, so that the
work can spring back to its normal shape.
[Illustration: Fig. 15. Cylinder Lining mounted in Fixture for Boring]
[Illustration: Fig. 16. Detrick & Harvey Horizontal Boring Machine of
the Floor Type Boring Engine Bed Casting]
=Horizontal Boring Machine of Floor Type.=--The type of horizontal
boring, drilling and milling machine, shown in Fig. 16, is intended for
boring heavy parts such as the cylinders of large engines or pumps, the
bearings of heavy machine beds and similar work. This machine can also
be used for drilling and milling, although it is intended primarily for
boring, and the other operations are usually secondary. This design is
ordinarily referred to as the "floor type," because the work-table is
low for accommodating large heavy castings. The spindle _S_ which drives
the boring-bar, and the spindle feeding mechanism, are carried by a
saddle. This saddle is free to move vertically on the face of column
_C_ which is mounted on transverse ways extending across the right-hand
end of the main bed. This construction permits the spindle to move
vertically or laterally (by traversing the column) either for adjusting
it to the required position or for milling operations. The spindle also
has a longitudinal movement for boring. There is an outer bearing _B_
for supporting the boring-bar, which also has lateral and vertical
adjustments, so that it can be aligned with the bar.
The work done on a machine of this type is either clamped directly to
the large bed-plate _A_ (which has a number of T-slots for receiving the
heads of the clamping bolts) or, in some cases, a special fixture may be
used or an auxiliary table. Boring machines of this same general
construction are built in many different sizes. The main spindle of the
machine illustrated is driven by a motor located at the rear of the
vertical column _C_, the motion being transmitted to the spindle through
shafts and gearing. The casting _D_, shown in this particular
illustration, is for a steam engine of the horizontal type, and the
operation is that of boring the cylindrical guides or bearings for the
crosshead. These bearings have a diameter of 15-3/4 inches and are
37-3/4 inches long. In boring them, two roughing cuts and one finishing
cut are taken. The end of the casting, which in the assembled engine
bears against the cylinder, is then faced by means of a regular facing
arm.
After removing the boring-bar the table _E_ of the special fixture on
which the casting is mounted is turned one quarter of a revolution. A
large milling cutter 24 inches in diameter is next mounted on the
spindle of the machine, and one side of the main bearing, as well as the
pads for the valve-rod guide-bar brackets, are milled. The table is then
revolved and the opposite side of the main bearing is milled in the same
way, the table being accurately located in the different positions by an
index plunger _F_ which engages holes on the under side. The spindle is
now moved upward to allow the table to be turned so as to locate the
bearing end of the frame next to the headstock of the machine. The
milling cutter is then used to machine the inside and top surfaces of
the main bearing. By turning the fixture and not changing the position
of the casting after it is bolted into place, the various surfaces are
machined in the correct relation to one another without difficulty. This
is a good example of the work done on horizontal boring machines of the
floor type.
INDEX
PAGE
Acme flat turret lathe, examples of chuck work 219
Acme standard thread and tool for cutting 159
Acme standard thread gage 157
Acme thread tool, measuring width with vernier caliper 157, 158
Accumulation of errors 105, 106
Aligning lathe centers for cylindrical turning 16
Allowances, average, for forced fits 130
for different classes of fits 131
for driving fits 131
for forced fits of given pressure 133
for push fits 131
for running fits 131
for shrinkage fits 133
Aluminum, lubricant for machining 53
shape of tools for turning 53
speed and feed for machining 53
Angle-plate applied to lathe faceplate 48
Angles, gage for accurate measurement of 97
Apron of lathe 4, 5
Arbor or mandrel press 22
Arbors or mandrels for lathe work, types of 19
use of 17
Attachment, application of Hendey relieving 125
convex turning for vertical boring mill 259
for coarse threading in lathe 160
for spherical turning 113
for taper turning in lathe 88
Hendey relieving 123
Automatic chucking and turning machine, Potter & Johnston 223
Potter & Johnston, method of "setting-up" 227
Potter & Johnston, turning flywheel in 236
Back-gears of lathe 3, 4
Bardons & Oliver turret lathe, general description 178
Bored holes, measuring diameter of 41
Boring and reaming tools for vertical mill 251
Boring and turning mill, vertical, general description 242
vertical, holding and setting work 247
vertical, turning in 249
Boring and turning mill, vertical, turning tools for 253
Boring-bar cutters and methods of holding 280
Boring cutters for roughing and finishing cuts 285
Boring cylinders on horizontal machine 286
Boring holes to given center distance in lathe 51
Boring in lathe, example of 39
Boring large castings in lathe 49
Boring large holes, cutter-heads used for 283
Boring machine, horizontal 275
horizontal, examples of work on 289-297
horizontal, floor type 294
vertical, multiple-spindle type 274
Boring tool, lathe 40
Box-tools, different designs and examples of work 193
for general turret lathe work 190
Bradford belt-driven lathe, general description 1
Bradford quick change-gear type of lathe 173
Brass, speed for turning 52
tool for turning in lathe 52
"Bridle" or "hold-back" for lathe 26, 27
Bullard vertical turret lathe 264
examples of work 268
Button method of locating work 101
Caliper tool for taper turning 85
Calipers, methods of setting 10, 11
"Cat-head," application in lathe work 25
Center holes, incorrect and correct forms 32
Center indicator, use of 100
Centered stock, methods of facing ends 34
Centers, lathe, aligning for cylindrical turning 16
lathe, grinder for truing 34
Centering machine 30
Centering parts to be turned 28
Centering, precaution for tool steel 33
Change gears, calculating for thread cutting 167
compound, for thread cutting 170
for cutting fractional threads 171
for cutting metric pitches 171
for thread cutting 135
Chasing dial for "catching threads" when screw cutting 141
Chuck, inaccuracy from pressure of jaws 42
lathe, application of 37
setting work in 42
universal, independent and combination 36
Chucking and turning machine, Potter & Johnston automatic 223
Potter & Johnston automatic, method of "setting-up" 227
Potter & Johnston automatic, turning flywheel in 236
Chucking machine, New Britain, multiple-spindle type 238
Clearance angle for turning tools 66
Clearance of turning tools, meaning of 62, 63
Coarse threading attachment for lathe 160
Collapsing tap, Geometric 202
Combination chuck for lathe 36
Compound rest, applied to screw or thread cutting 143
applied to taper turning 95
Convex turning attachment for vertical boring mills 259
Copper, tool for turning in lathe 52
Crankshaft lathe, description of R. K. LeBlond special 108
operation of R. K. LeBlond 110
Crankshaft turning in engine lathe 107
Cross-slide stop for threading 155
Cuts, average depth for turning 75
roughing and finishing in lathe 12, 75, 76
Cutter-heads, for boring, equipped with adjustable tools 284, 285
for horizontal boring machine 283
Cutters, boring, roughing and finishing types 285
for boring-bars 280
Cutting lubricants for turning tools 77
Cutting speeds, average for turning 72
based on Taylor's experiments 71
effect of lubricant on 76
factors which limit speeds for turning 72
rules for calculating 74
Cylinder boring machine, multiple-spindle type 274
Cylinder boring on horizontal machine 286
Cylinder lining, fixture for holding when boring 293
Cylindrical turning, simple example of 6
Davis turret lathe, turning bevel gear blanks 212
turning worm-gear blanks 211
Depth of cut for turning, average 75
Detrick & Harvey horizontal boring machine, floor type 294
Dial for "catching threads" when screw cutting 141
Dial gage, testing concentricity of button with 103, 104
Die and tap holders, releasing 199
Die-heads, self-opening type 200
Disk gage, for angles and tapers 97
rules for setting 98, 99
Dogs or drivers, lathe, application of 16
Drill, flat, for lathe 44
Drilling and reaming in lathe 43
Drivers or dogs, lathe, application of 16
Driving fits, allowances for 131
Eccentric turning in lathe 106
Engine lathe, general description 1
Errors, accumulation of 105, 106
Faceplate, indexing for multiple-thread cutting 153
lathe, application of angle-plate to 48
lathe, holding work on 45
Facing ends of centered stock, different methods 34
Feed and depth of cut for turning, average 75
Feeds and speeds for turning based on Taylor's experiments 71
Filing and polishing in lathe 13
Finishing and roughing cuts in lathe 75, 76
Fits, allowances for different classes 131
different classes used in machine construction 129
driving, allowances for 131
forced, allowances for given pressure 133
forced, average allowance for 130
forced, pressure for 132
push, allowances for 131
running, allowances for 131
shrinkage, allowances for 133
Fixture for holding thin lining when boring 293
Flat drill and holder for lathe 44
Flat turret lathe, Acme, examples of chuck work 219
Hartness, example of turning 213
Jones & Lamson double-spindle type 221
Floating reamer holders 271
Flywheel, finishing in one setting in turret lathe 186
finishing in two settings in turret lathe 189
machining in turret lathe 184
turning in Potter & Johnston automatic 236
turning in vertical boring mill 255
Follow-rest for lathe 27
Forced fits, allowances for given pressure 133
average allowance for 130
pressure generally used in assembling 132
Fractional threads, change gears for cutting 171
Gage, disk, for angles and tapers 97
disk, rules for setting 98, 99
for testing V-thread tool 138
standard plug, for holes 42
thread, Acme standard 157
Geometric collapsing tap 202
Geometric self-opening die-head 200
Gisholt convex attachment for vertical mill 259
Gisholt vertical boring mill, general description 242
Grinder for truing lathe centers 34
Grinding lathe tools 62
Hartness flat turret lathe, example of turning 213
Hendey relieving attachment 123
application of, for relieving taps, cutters and hobs 125
"Hold-back" or "bridle" for lathe 26, 27
Hollow mills for turret lathe 198
Horizontal boring machine 275
Detrick & Harvey floor type 294
examples of work 289-297
Independent chuck for lathe 36
Index plate, change gear, for lathe 137
Indicator, center, use on lathe 100
for "catching threads" when screw cutting 141
test, truing buttons with 102, 103
thread, for lathe apron, principle of 142
Inserted cutter turning tools for lathe 58
Internal threading 154
Jones & Lamson double-spindle flat turret lathe 221
Knurling in lathe and tool used 122
Lard oil as a cutting lubricant 78
Lathe, boring holes to given center distance in 51
boring large castings in 49
boring small hole with 104, 105
cutting threads in 135
drilling small hole with 104
general description of Bradford 1
LeBlond crankshaft, operation of 110
Lo-swing, general description 115
method of handling when cutting threads 138
quick change-gear type 173
R. K. LeBlond special crankshaft 108
turret type, general description 178
Lathe centers, grinder for truing 34
Lathe chucks, application of 37
universal, independent and combination 36
Lathe faceplate, holding work on 45
Lathe follow-rest 27
Lathe steadyrest 23
application of, when boring 25
Lathe taper attachment 88
practical application of 90
Lathe tool grinding 62
Lathe tools, angle of clearance 66
angle of keenness 67
application of various types 56
slope of cutting edge 66, 67
Lathe turning tools, inserted-cutter type 58
set of tools for general work 54
Lead of thread, definition of 146
LeBlond, R. K., lathe for crankshaft turning 108
Left-hand thread, method of cutting 148
Lining, fixture for holding when boring 293
Lo-swing lathe, general description 115
example of multiple-turning 117
Lubricant, effect on cutting speed 76
for cooling turning tools 77
for machining aluminum 53
lard oil as a cutting 78
Lucas horizontal boring machine 275
Mandrel or arbor press 22
Mandrels or arbors for lathe work, types of 19
for lathe work, use of 17
Metric pitches, change gears for cutting 171
Micrometer for measuring threads 162
Mills, hollow, for turret lathe 198
Multiple-spindle chucking machine, New Britain 238
Multiple-thread cutting, indexing faceplate for 153
Multiple threads 146
method of cutting 150
setting tool when cutting 152
Multiple-turning in Lo-swing lathe 117
New Britain multiple-spindle chucking machine 238
Newall Engineering Co's fit allowances 131
Pistons, gasoline engine, turning in turret lathe 204
Piston rings, attachment for turning in turret lathe 210
turning in turret lathe 206
Piston turning in Pratt & Whitney turret lathe 208
Pitch, metric, change gears for cutting 171
Pitch of thread, definition of 146
Plug gage, standard 42
Polishing and filing in lathe 13
Potter & Johnston automatic chucking and turning machine 223
method of "setting-up" 227
turning flywheel in 236
Pratt & Whitney turret lathe, arranged for piston turning 208
equipped with piston ring turning attachment 210
Press for arbors or mandrels 22
Pressure generally used in assembling forced fits 132
Push fits, allowances for 131
Quick change-gear type of lathe 173
Reamer holders, floating type 271
Reaming and drilling in lathe 43
Releasing die and tap holders 199
Relieving attachment, Hendey 123
Relieving attachment, Hendey, application of 125
Relieving hobs or taps having spiral flutes 128
Rivett-Dock threading tool 164
Roughing and finishing cuts in lathe 75, 76
Running fits, allowances for 131
Screw cutting, calculating change gears for 167
compound gearing for 170
in engine lathe 135
method of handling lathe 138
selecting change gears for 135
with compound rest 143
Screws, cutting to compensate for shrinkage 165
metric, change gears for cutting 171
testing size of 161
Selecting type of turning machine 240
Shrinkage, cutting screws to compensate for 165
Shrinkage fits, allowances for 133
Side-tool, facing with 7
Speeds for turning, average 72
based on Taylor's experiments 71
effect of lubricant 76
factors which limit 72
rules for calculating 74
Spherical turning 111
attachments for 113
"Spider" for supporting bushing while turning 48, 49
Spiral flutes, method of relieving hobs or taps with 128
Square thread and method of cutting 149, 159
Steadyrest, application of when boring 25
for engine lathe 23
Stop for lathe cross-slide when threading 155
Tap and die holders, releasing type 199
Taper attachment for lathe 88
practical application of 90
Taper boring with taper attachment 90
Taper threading, position of tool for 154
Taper turning, adjustment of tailstock center for 82
by offset-center method 80
examples of 83
height of tool for 94
in vertical boring mill 261
in vertical mill with horizontal and vertical feeds 262
setting tailstock center with caliper tool 85
setting tailstock center with square 87
with compound rest 95
with taper attachment 92, 93
Tapers, gage for accurate measurement of 97
Tapers, rules for figuring 97
Test indicator, truing buttons with 102, 103
Test or center indicator for use on lathe 100
Thread cutting, calculating change gears for 167
compound gearing for 170
cross-slide stop used for 155
indexing faceplate for multiple threads 153
in engine lathe 135
internal 154
method of handling lathe 138
selecting change gears for 135
taper, position of tool for 154
with compound rest 143
Thread gage, Acme standard 157
Thread indicator for lathe apron 141, 142
Thread micrometer 162
Thread tool, Acme, measuring width with vernier caliper 157, 158
for cutting V-thread 138
Thread tools for standard threads 159
Threads, Acme standard, and tool for cutting 159
change gears for fractional 171
cutting to compensate for shrinkage 165
different forms of 144
left-hand, method of cutting 148
metric, change gears for cutting 171
multiple 146
multiple, method of cutting 150
multiple, setting tool when cutting 152
sharp V, and tool for cutting 159
square, and method of cutting 149, 159
testing size of 161
three-wire system for measuring 163
U. S. standard, and tool for cutting 146, 159
Whitworth standard, and tool for cutting 158, 159
worm, and tool for cutting 159, 160
Threading attachment, lathe, for coarse threads 160
Threading tool, Rivett-Dock 164
Tool grinding 62
Tools for lathe, set for general turning 54
Tools for turning, angle of clearance 66
angle of keenness 67
inserted-cutter type 58
slope of cutting edge 66, 67
Tools for turret lathe 190
Tools, lathe, application of various types 56
Turning, cylindrical, simple example of 6
eccentric 106
multiple, in Lo-swing lathe 117
with front and rear tools 114
Turning speeds, average for lathe 72
based on Taylor's experiments 71
factors which limit 72
rules for calculating 74
Turning tools, angle of clearance 66
angle of keenness 67
for aluminum 53
for brass 52
for copper 52
for lathe, position of 60
for lathe, set of, for general work 54
inserted-cutter type for lathe 58
slope of cutting edge 66, 67
Turret lathe, Bardons & Oliver, general description 178
examples of chuck work in Acme flat 219
Hartness flat, example of turning 213
Jones & Lamson double-spindle type 221
machining flywheels in 184
Pratt & Whitney arranged for piston turning 208
piston ring turning attachment for 210
tools for general work 190
turning bevel gear blanks in Davis 212
turning gasoline engine pistons in 204
turning piston rings in 206
turning worm-gear blanks in Davis 211
typical example of turret lathe work 181
Turret lathe tools, miscellaneous types 202
Turret lathe type of vertical boring mill 264
Type of turning machine, factors which govern selection 240
U. S. standard thread 159
method of cutting 146
Universal chuck for lathe 36
V-thread and tool for cutting 159
Vertical boring mill, Bullard turret lathe type 264
convex turning attachment 259
general description 242
holding and setting work 247
taper turning in 261
taper turning with horizontal and vertical feeds 262
tools for boring and reaming 251
turning flywheel in 255
turning tools for 253
Vertical turret lathe, Bullard, examples of work 268
Whitworth standard thread and tool for cutting 158, 159
Wire system for measuring threads 163
Worm thread and tool for cutting 159, 160
Transcriber's notes on changes made to text:
Left as in original:
use of degree, deg. and deg.; use of minute, min. and '.
Standardised to the most commonly used in the book:
backgear to back-gear; camshaft to cam-shaft; crankpin to
crank-pin; face-plate to faceplate; out-board to outboard;
over-hang to overhang; setscrew to set-screw; steady-rest
to steadyrest; subdivision(s) to sub-division(s); tail-stock
to tailstock; thumbscrew to thumb-screw; tool-post to toolpost;
tool-slide to toolslide; hand-wheel to handwheel; U.S. to U. S.
Page 64 had a blotched (illegible) word, this has been replaced by
(large and rigid) work.
Table of Contents: largely re-compiled to create one-to-one links
with named paragraphs and sections in text.