MACHINES AND TOOLS FOR SHRAPNEL MANUFACTURE
=Reed-Prentice Co. Equipment for Machining Forged Shrapnel Shells.=--In
machining the 18-pound British shrapnel shell on the equipment
furnished by the Reed-Prentice Co., Worcester, Mass., eight distinct
operations are performed as follows: First, drilling a center hole
in the closed end of the forging in a Prentice 16-inch ball-bearing
sensitive drilling machine equipped with a special centering fixture;
second, rough-turning the outside diameter, grooving, squaring the
closed end and rounding the corners in a Reed-Prentice 14-inch heavy
type automatic lathe; third, machining the powder pocket and diaphragm
seat, as well as the internal and external diameters of the nose in
a 14-inch Reed extra-heavy turret lathe; fourth, under-cutting band
grooves and producing wave ribs in a 14-inch Reed engine lathe; fifth,
boring, reaming, threading and facing the open end in a Reed 14-inch
extra-heavy turret lathe; sixth, finish-turning outside diameter and
radius on nose, also form-turning copper band in a Reed 14-inch heavy
type automatic lathe; seventh, cutting off center projection on closed
end of shell in a Reed 14-inch engine lathe; eighth, finishing brass
socket to form, cleaning inside of socket and cutting off excess length
of tube in a Reed 14-inch extra-heavy turning lathe.
=First Operation on Rough Shell Forging.=--The drilling of the center
hole in the closed end of the forging is a comparatively simple
operation, and is performed in an interesting fixture held on a 16-inch
Prentice ball-bearing sensitive drilling machine. This fixture, which
is designed for handling the work quickly, is shown in Fig. 1, and
consists of the base casting _A_ clamped to the table of the drilling
machine. The entire back part of the jig swings on the trunnion _B_ to
provide a means for quickly removing the forging _C_ from the arbor
_D_. A locking-pin _E_ is used for locating the fixture in its upright
position for drilling. Bushing _G_ in the top plate _F_ of the fixture
guides the combination drill and countersink.
[Illustration: Fig. 1. Fixtures used for holding Shrapnel Shell
Forgings when drilling Center Hole in a 16-inch Prentice Ball Bearing
Sensitive Drilling Machine]
The construction of the work-holding arbor is worthy of special
attention. This arbor _D_ has a cap _H_ on its top end that acts as a
stop for the inside of the forging, which, in being placed over the
arbor, is located centrally and clamped by fingers _N_. To operate
these fingers, hand lever _I_ is depressed, and as this is fulcrumed
at the point _J_, it causes collar _K_ to rise on the arbor. Yoke _L_
forms a connection between the lever and the collar with which the
sleeve carrying fingers _N_ is integral. Fingers _N_ are fulcrumed in
arbor _D_ and are thrown outward to grip the forging when sleeve _M_
is raised. Light springs _O_ tend to keep the gripping fingers in a
vertical position against the arbor when they are not being forced
outward by the inclined surfaces on sleeve _M_. Handle _I_ carries a
spring pawl _P_ that holds the sleeve _M_ stationary while the forging
is being center-drilled.
[Illustration: Fig. 2. Tool Lay-out for performing Second Series of
Operations on Reed-Prentice Heavy Type Automatic Lathe]
=Second or Rough-turning and Facing Operations.=--The second operation
is performed on a Reed-Prentice 14-inch heavy type automatic lathe,
as shown in Figs. 2 and 3. The forging _A_ is held on an internal
expanding arbor _B_, the driving part of which is supported by
the head-center. At the closed end, the shell is steadied by the
tail-center. The bottom of the shell rests against the end of the
arbor which acts as a gage. In this setting, the external diameter of
the forging is rough-turned by four tools _F_, mounted on the carriage
_G_. This carriage has a travel slightly less than two inches, and an
automatic throw-off is provided at the end of the cut that disengages
the tools, draws them back and returns the carriage. At the rear of
the carriage on this machine a facing arm is mounted on a heavy bar.
Turning tools are carried on this facing arm, as shown, and when the
front carriage feeds longitudinally a cam bracket _O_, bolted to the
carriage, is carried along with it. Clamped on this bracket is an
adjustable cam _N_ held in place by screws. Cam roll _M_ on the facing
arm contacts with cam _N_, causing the facing arm to rock forward as
the carriage travels longitudinally.
[Illustration: Fig. 3. Section through Reed-Prentice Automatic Lathe,
showing Tool Arrangement]
Referring to the plan view in Fig. 2, tool _H_, held in the arm, faces
the end of the forging, tool _I_ chamfers the corner, and tool _J_ cuts
the depression for the wave ribs, leaving a projection in the center
from which the ribs are formed. It should be understood that the tools
on the carriage and facing arm work together. One man can run two of
these machines without trouble.
=Third Series of Machining Operations.=--The third series of operations
on the shrapnel forging is performed on a 14-inch Reed heavy lathe with
a specially large turret, as shown in Fig. 4. This lathe is fitted
with a 12-inch three-jaw chuck, bored out to 3¹⁄₂ inches to permit
the forging to extend into it. The forging _A_ is put in the chuck
as shown at _B_, and the jaws grip at _C_. The first operation is
performed with a bar _D_ carrying a blade cutter _E_ that rough-bores
the powder pocket, and tool _F_ that rough-bores the mouth. The turret
is now indexed, and a boring-bar carrying a blade _G_ roughs out the
diaphragm seat, while an auxiliary tool _H_ faces the shell to length.
At the next indexing of the turret the boring-bar _I_ that carries the
finishing tool _J_ finishes the diaphragm seat and powder chamber.
[Illustration: Fig. 4. Tooling Equipment for performing Third Series of
Operations on 14-inch Extra-heavy Turret Lathe]
[Illustration: Fig. 5. Tools used for Under-cutting and Waving Band
Grooves on Reed 14-inch Engine Lathe]
=Fourth Operation--Under-cutting and “Waving” Band Groove.=--For the
fourth operation, the forging is held in a 14-inch Reed engine lathe
provided with an automatic attachment for under-cutting and waving the
ribs for the copper band. The tool equipment used is shown in Fig. 5,
where _A_ is the forging held by one end in the chuck and supported
on the opposite end by the tail-center. The tools are all located in
holders on the heavy base block _B_, and their operation is controlled
from the carriage _R_ of the lathe. The cutting of the wave ribs is
done by tool _C_ at the front, held on a slide that operates on the
top of block _B_. Spring _D_ keeps the roll _E_ on the lower slide of
the tool-holder in contact with the cam slot in cam-plate _F_ that is
fastened to carriage _R_. When the carriage is traversed toward the
chuck, the irregular surface of cam-plate _F_ engages the roll and
forces the tool-holder forward. Side motion to produce the wave is then
effected by face-cam _G_, mounted on the chuck and contacting with the
roll _H_. This roll is supported on a bracket forming an auxiliary
slide _S_ that carries the waving tool _C_. A stiff barrel spring keeps
slide _S_ in contact with the cam _G_. Thus, when the machine spindle
revolves, the auxiliary slide is caused to oscillate back and forth far
enough to give the desired amount of wave.
The under-cutting in the band groove is accomplished by tools _I_ and
_J_ which are mounted on separate tool-slides _K_ and _L_. These slides
are fed in at an angle to the axis of the forging, against the action
of coil springs _M_ and _N_, by the cam surfaces of plate _Q_ in which
rolls _O_ and _P_ work. Plate _Q_ is bolted to carriage _R_ which, in
advancing toward the chuck, forces in the under-cutting tools in the
manner just described. The tail-center of this machine is fitted with a
quick-acting mechanism so that it may be withdrawn quickly to insert a
new piece.
=Fifth Series of Operations.=--Before performing the fifth series of
operations, the forging is heated and closed in on the nose. It is then
handled in the following manner: A Reed 14-inch heavy lathe, equipped
with an extra large turret mounted on a special wide-bridge carriage
carries tools for boring, reaming, threading and final squaring of the
open end, as shown in Fig. 6. The shell forging for these operations
is held in a three-jaw chuck provided with special jaws. In the first
position the rough-boring of the nose and the rough-facing of the
extreme end is performed with tools _B_ and _C_. The turret is then
indexed and tools _D_ and _E_ finish-ream the hole in the nose and face
the end. The tap _F_ is next brought into position, cutting the thread
in the nose.
[Illustration: Fig. 6. Turret Tools held on Reed 14-inch Extra-heavy
Lathe for performing Fifth Series of Operations]
The turret is again indexed, bringing a special form boring tool into
position. Here the boring tool _G_ is carried in a bar _H_ held in a
holder of the cross-sliding carriage type that is fastened to two faces
of the turret. By means of cross-screw _J_, the boring tool _H_ may be
drawn in or out at will. This tool operates as follows: As the turret
is advanced, handle _J_ is operated to let tool _G_ enter the nose of
the shell, and, upon the continued advance of the turret, arrow head
_M_ is forced in between and gripped by the fingers _N_. The turret is
now backed away from the chuck, and while receding acts upon slide _P_
through the medium of roll _L_ and cam groove _R_. The plate containing
cam groove _R_ is attached to the arrow head _M_ and consequently is
held stationary while the turret is being withdrawn from the work. This
backward movement of the turret is continued until the tool _G_ is
withdrawn from the work and slide _S_ comes in contact with check-nuts
on rod _O_, withdrawing arrow head _M_ from fingers _N_ and allowing
the turret to be indexed ready for the first operation on the next
forging.
[Illustration: Fig. 7. Reed-Prentice 14-inch Heavy Type Automatic Lathe
used for performing Sixth Series of Operations]
=Sixth or Finish-turning Operations.=--The sixth series of operations
is performed on a Reed-Prentice 14-inch heavy type automatic lathe,
similar to that used for the second operation, and the machine is
also operated in a manner similar to that previously described. The
operations consist in finish-turning the outside diameter of the shell
and turning the radius on the nose. In addition, the copper rifling
band, put on previous to this operation, is turned to shape. Referring
to Fig. 7, the shrapnel shell _A_ is held by the tail-center at one end
and is supported and driven from the other end by a plug screwed into
it. This plug is held on the live center and is driven by an equalizing
driver, coming in contact with pins in the special faceplate.
[Illustration: Fig. 8. Tools for machining Brass Fuse Socket on 14-inch
Heavy Turning Lathe--Eighth Operation]
Two slides _B_ and _C_ are carried on the front of the carriage. Slide
_C_ carries three tools _D_; two of these start in from the rifling
band and turn in toward the nose, and the other works up toward the
rifling band from the closed end. Tool _E_, carried in slide _B_,
turns the curve on the nose of the shell and is controlled in its
action by means of a slot in cam _F_ in which a roller held to the
slide operates. At the rear of the carriage is carried a facing bar
attachment, as previously described in connection with the second
operation. This attachment carries three tools, as illustrated,
for machining the rifling band to shape, facing the closed end and
chamfering the corner.
=Seventh and Eighth Operations.=--After the sixth operation, the fuse
tube is threaded into the diaphragm, the bullets put in, and the hot
resin poured in to keep them from rattling. The brass socket is then
screwed into the nose and the fuse tube soldered to it. The shell is
now ready for the seventh operation which consists in cutting off the
center projection. This is accomplished in a Reed 14-inch engine lathe,
provided with a faceplate chuck for holding and driving the shell at
the open end, and a steadyrest for supporting it close to the point
where the cutting is being done. The shell is now ready for the eighth
operation, which consists in machining the brass socket to shape in an
extra-heavy lathe as shown in Fig. 8. The tools used for machining are
retained in a special holder on the carriage. Tool _A_, which is used
for facing off the fuse tube and the brass socket, is inverted, starts
at the center and is fed out toward the circumference. The external
surface of the socket is machined with a circular forming tool _C_ held
on a stud _D_ located in block _B_. The inward travel of this tool is
limited by stop _E_ coming in contact with the shell.
[Illustration: Fig. 9. Shrapnel Case made from Chrome-nickel Steel
having High Tensile Strength on a Cleveland Automatic Screw Machine
with Special Tool Equipment]
[Illustration: Fig. 10. Order of Operations on the Shrapnel Case]
=Making Shrapnel Shells on the Cleveland Automatic.=--An unusual
example of automatic machine work is that of producing the shrapnel
shell shown in Fig. 9. This shell is made from a bar of 3¹⁄₁₆ inch
chrome-nickel steel stock. The steel has a tensile strength varying
from 125,000 to 135,000 pounds per square inch, and is extremely tough.
The work is accomplished on a 3¹⁄₄-inch Cleveland automatic, and the
tooling equipment, as shown in Figs. 10, 11, and 12, is interesting.
While the general operation of the Cleveland automatic is well
understood by many mechanics, the production of this piece illustrates
a number of points in the operation of this machine which are not so
well known. Therefore, it is advisable to explain in detail just how
this interesting job is handled.
[Illustration: Fig. 11. Cleveland 3¹⁄₄-inch Automatic Screw Machine set
up for making a Shrapnel Case in Twenty-five Minutes]
The first operation, as the job was originally laid out, was to feed
the stock out to the stop _A_, shown in Fig. 11, which is held on the
cross-slide and operated by a lever on the base of the machine. This
method has been improved upon since the photograph shown in Fig. 11
was taken, and the time reduced from twenty-seven and one-half minutes
to twenty-five minutes (see Fig. 10 for improved method). The second
operation is to rough-drill the large hole with an inserted bit _B_,
step the hole for the taper reamer with cutter _C_ and rough-turn the
external diameter with cutter _D_ held in a special turning attachment.
This attachment envelops the shanks of all six tools in the turret in
order to obtain support. The cutters in the attachment shown in Fig.
11 work in advance of the under-cutting forming tool _E_ shown in Fig.
12, which is held on the rear cross-slide. The time required for the
completion of the operations outlined is thirteen minutes.
[Illustration: Fig. 12. Showing Tools held on the Front and Rear
Cross-slides for performing the Knurling, Forming, and Cutting-off
Operations on the Shrapnel Case]
In the third operation drill _H_ finishes the powder pocket, and two
cutters _I_ counterbore for the tap--time required three minutes. The
fourth operation consists in finishing the diaphragm seat with the
counterbore _J_, finishing the front end with inserted cutter _K_ and
breaking the corner to facilitate tapping with inserted cutter _L_,
the time required being forty-five seconds. In the fifth operation the
thread is cut with a tap _M_ held in the tap-holder _N_ in forty-five
seconds. Then the turret is indexed and for the sixth operation the
hole is taper-reamed with reamer _O_, provided with four inserted
“Novo” steel blades, in ninety seconds. The last and seventh operation
consists in knurling the band with a knurl _P_ (see Fig. 12) mounted on
the front cross-slide, and cutting off the shell with a cut-off blade
_Q_ retained in a holder on the rear cross-slide--time six minutes.
The total time required to produce this shrapnel case by the improved
methods illustrated by the diagram in Fig. 10 is twenty-five minutes.
There are several points of unusual interest in the production of this
shrapnel case. One is the large amount of stock to be removed to form
the hole; the second is the long taper-reaming operation--difficult
work to accomplish satisfactorily on an automatic screw machine--and
the third is the long outside forming operation which must be held to a
limit of 0.0005 inch on the diameter. In order to accomplish this last
operation successfully, the external diameter of the piece is first
turned with a cutter held in a separate turning attachment, leaving
only 0.010 inch on the diameter to be removed by a wide under-cutting
or shaving tool _E_ held very rigidly on the rear cross-slide. Not
only must the case be exact as regards diameter, but it must not vary
from one end to the other nor at any point throughout its length. The
large shaving tool held rigidly in the manner illustrated in Fig. 12
accomplishes this result satisfactorily.
The material from which the case is made is so tough that some
difficulty was met with in selecting a tool steel that would stand up
for a reasonable length of time under cut. The drills and counterbores
are tipped with “Novo” cutters and all the forming tools, including
the cut-off tool, are also made from the same steel. The only cutting
tool in the entire tooling equipment not made of this steel is the
tap. The bar is rotated at sixty-four revolutions per minute, giving a
surface speed for the external cutting tools of approximately fifty-one
surface feet per minute.
[Illustration: Fig. 13. First Operation on Shrapnel Shell, performed on
a No. 6A Potter & Johnston Automatic Chucking and Turning Machine]
=Machining the British Forged Shell on Potter & Johnston
Automatics.=--In making the British forged shell on the Potter &
Johnston automatic chucking and turning machine, three operations
complete the work. The first operation completes the outside of the
shell, except for the extreme end which is covered by the gripping
mechanism of the chuck. The second operation finishes the inside of the
shell and at the same time finish-turns the extreme open end. After
the second operation is performed the shell is “nosed,” which consists
in heating it in a lead bath and then striking it under a light press
to close in the end. The third operation then follows, and consists in
taking light cuts from the inside diameter and threading the open end
of the shell.
[Illustration: Fig. 14. Expanding Arbor and Chucking Mechanism used
on Potter & Johnston Automatic Chucking and Turning Machines for
performing First Operation on Forged Shrapnel Shells]
[Illustration: Fig. 15. Set-up on a No. 6A Potter & Johnston Automatic
Chucking and Turning Machine for First Operation on Forged Shrapnel
Shells]
=Method of Holding Shell for First Operation.=--For the first
operation, the shell is held on an expanding arbor of the type shown in
Fig. 14. The arbor _A_ is tapered on its rear end and is held in the
nose of the spindle of the machine. The shell is pushed onto this
arbor until the end of the arbor strikes the bottom of the shell. The
gripping mechanism which comprises six jaws _B_ and a draw-in plunger
_C_ is contained inside the arbor. The external diameter of the arbor
is machined to practically the same shape as the internal diameter of
the shell, but is smaller. The jaws are held in slots which control
their movement in every direction except radially. They are forced out
radially by means of the draw-in bar _C_ which is provided with tapered
seats that engage the inward end of the jaws. The bar _C_ is operated
by a hand lever _D_ that extends up over the top of the machine, is
fulcrumed in a bracket on the rear bearing cap, and is connected to a
sliding sleeve _E_.
In clamping the work on the arbor, lever _D_ is lifted up, this action
drawing the sliding collar _E_ to the right along the sleeve _F_,
which, in turn, allows the forward end of the fingers _G_ to close
in. This releases the pressure of the outer end of the fingers on the
draw-in bar _C_. When the pressure from bar _C_ is released by means of
handle _D_, heavy coil springs _H_ then come into action forcing the
draw-in bar back and expanding the clamping jaws. Additional clamping
means are provided by three set-screws which are brought to bear on the
work after it has been clamped in position by the jaws. To release the
work, the reverse action takes place, that is, lever _D_ is forced down
which slides the collar _E_ to the left, operating the fingers _G_,
which, in turn, overcome the pressure of the springs _H_, allowing the
clamping jaws _B_ to collapse.
=First Machining Operation Set-up.=--The order of the first series of
operations in machining a forged shrapnel shell is as follows: First,
rough-turn 7 inches along body of shell, face end and chamfer; second,
finish-turn 2¹⁄₂ inches along shell; third, rough-groove for copper
band and dovetail; fourth, turn waves in groove.
For the first operation, the work is held on the expanding arbor
shown in Fig. 14, and the tool equipment, which is of an unusually
interesting character, is shown in Fig. 15. The first rough-turning
operation, accomplished by turret tool _A_, which is of the relieving
type to be described later, is held on the first face of the turret and
roughs down the body of the shell. On the opposite side of the holder
is a roller support _B_ which supports the shell while the turning tool
is in operation. The end of the shell is faced by means of a facing
tool _C_ which is really a type of facing mill. The end of the shell is
then chamfered by means of a chamfering tool _D_ that removes the sharp
corner.
[Illustration: Fig. 16. Details of Relieving Turning Tool-holder shown
in Fig. 15]
After these operations have been performed, the turret is indexed and
the second face of the turret is brought in line with the chuck. This
operation is accomplished with a relieving tool-holder _E_ carrying a
cutter _e_, which takes a cut 2¹⁄₂ inches along the body of the shell.
An interesting feature of this tool is that on the return stroke of the
turret it swivels back out of the way so that the shell is not scored
by the tool dragging over it. The construction of this tool is more
clearly shown in Fig. 16.
As is clearly shown in this illustration, the turret relieving turning
tool comprises a shank on which is fulcrumed a tool-holding member _B_.
This is slotted out to carry the turning tool _C_ which is clamped
in place by two set-screws _D_ and is adjusted to turn the correct
diameter by means of an adjusting stud and clamping nut _F_ and
_G_. The method of operating this tool is as follows: The fulcrumed
tool-holder _B_ is “held up” by means of a fillister-head screw,
screwed into a stud _H_ and acted upon by a coil spring _I_. A hole to
receive the stud is drilled in the tool-holder _B_, allowing about ¹⁄₁₆
inch clearance. When the tool is in action it has a reverse position
to that shown in the illustration, that is, the turning tool instead
of being parallel with the center line is at a slight angle with it.
In action, as soon as the turret advances, the tool comes into contact
with the work, and the work, turning around, forces the cutting tool
down and consequently depresses the spring, at the same time bringing
the “lower part” of the hole into contact with the extended plug on
the holder. In this way the tool is held rigidly and in contact with
the work. As soon as the turret begins to move back, however, and the
cutting pressure is released, the spring comes into action and throws
up the tool, bringing it out of contact with the work.
Upon the completion of the operation which is accomplished from the
second turret face, the turret is again indexed and the next operation
is performed from the rear cross-slide and the third turret face.
The third operation consists in cutting the grooves for the rifling
band, and, on account of the under-cutting necessary, involves some
interesting points. In order to hold the work rigidly while the
grooving tools are acting on it, a revolving support _F_ is brought
in from the turret. The wide tool _G_ for cutting the band grooves
(this tool removes the greatest amount of the stock) is held on the
rear cross-slide and is of the under-cutting type; that is to say, it
operates under the work or tangentially instead of radially. Held on a
bracket on the third turret face are two tools _H_ and _I_, the purpose
of which is to dovetail the rifling band grooves. These turret tools
are held in a holder working in a slide on the bracket fastened to the
turret face and are operated by a block held on the rear cross-slide.
The action of these three tools, therefore, is simultaneous. The wide
grooving tool, however, is slightly ahead of the dovetailing tools.
[Illustration: Fig. 17. Type of Draw-In Collet and Chucking Mechanism
for holding Forged Shrapnel Shell for performing Second Series of
Operations]
The last operation is accomplished when the turret is indexed to the
fourth position. Here, again, a roller support _J_ steadies the work
while the waving tool is in action on it. The two waves that are formed
are for the purpose of preventing the rifling ring from turning, and
they deviate about ¹⁄₁₆ inch laterally from being a true annular rib.
The tool for cutting these ribs is shown at _K_ and is of the forming
type held in a dovetailed groove in the holder _L_. This also carries
a roll _M_ which contacts with the waved surface of the face-cam _N_,
the curve of which gives the correct out-and-in motions to the waving
tool _K_. The cam face is on a sleeve that is threaded onto the nose of
the spindle of the machine, as is shown to the left of the illustration
opposite the first turret face.
=Method of Holding Shell for Second Operation.=--The second series of
operations on the shell is also performed on the Potter & Johnston
automatic chucking and turning machine. The shell is held at the base
end by a special collet of the draw-in type, as shown in Fig. 17.
Fixed in the nose of the spindle is a positive stop _A_ against which
the shell is held by means of the draw-in collet _B_. This collet
extends into the draw-in rod _C_, to which it is attached. The method
of operating this gripping mechanism differs slightly from that shown
in Fig. 14. In this case the spring collet _B_ is drawn into a tapered
sleeve to clamp it on the work. This is effected by means of lever _D_
which is fulcrumed in a bracket extending from the rear bearing cap of
the machine and operates a sliding cam sleeve _E_. The cam, in turn,
operates fingers _F_, only one of which is shown, the latter acting
upon the draw-in rod _C_ to which the collet is attached. By depressing
lever _D_, the chuck is opened by means of the coil springs _G_ which
act upon the draw-in rod _C_ when the pressure of the fingers has been
released. Lifting up handle _D_ closes the chuck, and depressing it
opens the chuck.
[Illustration: Fig. 18. Tooling Equipment used on No. 6A Potter &
Johnston Automatic Chucking and Turning Machine for performing Second
Series of Operations on Forged Shrapnel Shell]
=Second Series of Machining Operations on Shrapnel Shells.=--The
operations on the shrapnel shell performed in the second setting are
shown in Fig. 18. The relieving tool _A_, held on the first face of
the turret, covers that section of the shell which in the former
operation was held in the gripping jaws. While this cut is being taken,
a turret tool _B_ rough-bores the powder pocket and diaphragm seat.
The relieving tool _A_ is constructed and operated similarly to the
relieving tool described in connection with Fig. 16. It will be noted
here that the threads on the spindle nose are protected by a cast-iron
cap to prevent them from being injured. Upon the completion of the
operation just described, the turret is indexed, bringing the second
face in line with the spindle. Here the diaphragm seat is finished
with a flat cutter _C_, which is held in the boring tool illustrated.
The turret is again indexed into the third position, where the powder
pocket is finished by means of the flat cutter _D_.
The turret is now indexed to bring the fourth face in line with the
spindle where the extreme open end of the shell is turned taper by
means of a tool _E_ that is carried on the front cross-slide and
operated by the turret. By referring to this illustration, it will be
noticed that the taper is turned from the spindle toward the outer
end of the shell and is, therefore, a reverse turning operation. The
tool is caused to move toward the turret by using a rack and pinion to
reverse the movement. On this operation, as well as on the previous
one, one man takes care of four machines.
[Illustration: Fig. 19. Machining Inside of Shrapnel Shell, and
threading with Automatic Collapsible Tap on Potter & Johnston Automatic
Chucking and Turning Machine]
=Third Machining Operation on Shrapnel Shells.=--Before any other
machining operations are done on the shell, it is taken to a lead bath
where it is heated and afterward placed under a press which closes
in the nose or open end of the shell. For machining in the third
operation, the shell is held practically in the same manner as for the
second operation, except that it is gripped farther along the body.
The machining performed in this operation is as follows: On the first
turret face, rough-bore and finish-bore for a distance of 1 inch from
the end of the shell; second turret face, rough-bore the inside of
the shell for a distance of 1 inch back from the thread; third turret
face, finish-form on the inside for a distance of 1 inch back of the
thread; and fourth turret face, thread with a collapsible tap. The
various machining operations on the 3-inch size of shrapnel shells
are performed on a standard Potter & Johnston 6A automatic chucking
and turning lathe. It is recommended that these machines be run in
batteries or units of seven each, four machines being set up for the
first operation, two machines for the second operation, and one machine
for the third operation.
[Illustration: Fig. 20. First Series of Operations on “Frankford” Shell
on a Potter & Johnston 6A Automatic Chucking and Turning Lathe]
[Illustration: Fig. 21. Second Series of Operations on “Frankford”
Shell on Potter & Johnston Automatic Chucking and Turning Lathe]
=Machining “Frankford” Forged Shell.=--The machining of the American
or “Frankford” 3-inch type of high-explosive shrapnel shell is
comparatively easy, inasmuch as there is no nosing to be done, and the
entire shell may be machined at two settings. Fig. 20 shows the way
in which the first operation is taken care of on the No. 6A Potter &
Johnston automatic chucking and turning lathe. The forged shell is held
on an expanding arbor of the same type as that shown in Fig. 15. In
the first turret position, the operations consist in taking a straight
cut across the diameter and facing off the end. The external turning
tool _A_ is of the relieving type, and _B_ is a facing tool that works
on the end. Both of these tools are supported and operated from the
turret. A roll support, not shown, steadies the work while tool _A_
is working. The turret now backs out, and a forming tool, held on
the cross-slide, advances, cuts the rifling band and the semicircular
grooves in the end of the shell, and at the same time chamfers the
corner. Knurl _D_, held on the rear of the cross-slide, is then
advanced. This knurls the bottom of the rifling band groove.
By referring to Fig. 20, it will be seen that the grooves do not
extend entirely across the face of the knurl, but instead two “knurl”
ribs similar to a double thread are formed on the periphery. This
construction makes it possible to sink the knurl into the work to the
proper depth without exerting excessive pressure on the arbor and
throwing it out of line.
[Illustration: Fig. 22. Three-inch Shrapnel Shell made on a Gridley
Automatic Turret Lathe]
=Second Series of Operations on “Frankford” Forged Shrapnel
Shell.=--For the second series of operations, the “Frankford” shrapnel
shell is held in a draw-in collet as shown in Fig. 21. As the shell
has been completely machined on the outside, it is let into the collet
for a considerable distance. For machining, it is shown gripped in
the collet by jaws _A_ and is backed up by positive stop _B_. At the
first turret face, tool _C_ rough-bores the diaphragm seat, tool _D_
bores the thread diameter, and tool _E_ faces and chamfers the end.
The turret is now indexed, and tools _F_, _G_, and _H_ perform similar
finishing cuts. A holder held on the third turret face carries tool
_I_ that chamfers the powder pocket, and at the fourth turret face a
collapsible tap threads the open end.
[Illustration: Fig. 23. Tool set up for Producing the Shell shown in
Fig. 22]
=Making Shrapnel Shells on the Gridley Automatic Turret Lathe.=--Figs.
22 to 25 show a three-inch shrapnel shell made on the 3¹⁄₄-inch Gridley
single-spindle automatic turret lathe. The steel from which the shell
is made is very tough. The specifications are from 125,000 to 135,000
pounds tensile strength, 110,000 pounds elastic limit, a twenty-five
per cent reduction of area, and a twelve per cent elongation. It will
be seen from the above specifications that the steel is, of necessity,
very tough and difficult to work; in addition, a large taper reamer
must be used, and the outside of the shell must be relieved throughout
the central portion. It is also necessary to machine the piece to
extremely accurate dimensions, all of which tends to make the work
still more difficult. Fig. 22 shows a view of the shrapnel shell.
It is approximately three inches in diameter and eight inches long,
and the limits allowed for the sizes are extremely close throughout,
both inside and outside. Figs. 24 and 25 show the successive steps
employed in machining the piece complete, the four views presented
representing the appearance of the work and the operations performed at
each indexing of the turret. Fig. 23 will enable the operation of the
different parts to be more clearly understood.
[Illustration: Fig. 24. Successive Steps and Operations employed in
Making the Shell shown in Fig. 22]
[Illustration: Fig. 25. Successive Steps and Operations employed in
Making the Shell shown in Fig. 22]
While the operation of the Gridley automatic turret lathe is generally
understood by mechanics, it may be well to state briefly the general
principles upon which work is done in the single-spindle machine. In
this type of machine, the position of the work does not change as it
does in the multiple-spindle machine, but the turning is accomplished
by the operation of tools mounted on tool-slides which, in turn,
work on a turret that revolves about a horizontal axis, successively
presenting the tools for operation upon the work. This will be readily
understood by glancing at the illustration Fig. 23. It will also be
noticed from this illustration that the forming tools and cutting-off
tools are operated from a face-cam at the lower part of the machine.
The forming slide is actuated by a cam groove cut in one side of the
cam-plate while the cutting-off slide receives its movement from a cam
groove on the reverse side of this plate.
At the first position of the turret, a large 2¹¹⁄₃₂ inch high-speed oil
drill is run into the bar to a depth of 6¹⁄₃₂ inches, and, at the same
time, a knee-turner located on the tool-slide turns the outside of the
stock, thereby removing the scale from the bar. Referring to Fig. 23,
which shows the turret in the third position, the end of this large
drill is shown at _A_, and, of course, when at work, it would be in the
position of the reamer which is shown at _F_. The time elapsed at the
completion of this part of the work is eleven minutes, five seconds.
[Illustration: Fig. 26. First Chucking on Warner & Swasey Turret Lathe
for machining British Forged Shrapnel Shells]
At the second position of the turret, a smaller drill, 2¹⁄₁₆ inches
in diameter, which is shown at _B_, is run in at the bottom of the
hole previously drilled to a depth of ²⁹⁄₃₂ inch. At the same time a
counterboring tool, which is located at _C_ and which is attached to
the drill with a set-screw, is at work counterboring the end of the
hole in the shell. During the time that this drilling and counterboring
operation is being performed, the forming tool shown at _D_ is being
fed into the outside of the head of the shell, finishing the three
grooves as shown; in addition, a sizing tool _E_, which is at a fixed
distance from the forming tool, comes in and sizes the work to exactly
the right length. The time elapsed up to the finishing of this part of
the work is thirteen minutes, thirty-five seconds.
[Illustration: Fig. 27. Diagram Illustrating Position and Relation of
Tools for First Chucking on British Forged Shell]
At the third position of the turret, which, by the way, is the one
shown in Fig. 23, the large taper reamer _F_ is run in, which operation
removes the bulk of the stock for the taper, and a second step at the
end of this reamer finishes the extreme end of the hole at the bottom
of the shell. The blades of this reamer are nicked to break the chips
as they are being formed. Before the reamer begins to cut, the knurling
tool _H_ is brought against the work (while it is on the high speed)
by the cutting-off slide, which, of course, results in a better knurled
section than would result if the knurling of the piece were done at a
lower speed. During the reaming operation, the cutting-off tool _G_
is run in part way to facilitate the final severing of the piece. In
addition, the relieved part of the work is turned by a tool mounted in
a tool-holder on the slide of the turret. This tool is shown at _I_
and it is operated by a templet _J_ which has a raised projection that
throws the tool into the work after it has reached the right position
with relation to the length of the shell. The total time elapsed up
to the finishing of this part of the work is twenty-two minutes,
thirty-five seconds. At the fourth and last position of the turret, a
finishing reamer sizes the outer end of the interior of the shell and
is withdrawn but part way, so that, when the cutting-off slide comes in
and finishes severing the piece, the shell is caught on the reamer and
not allowed to drop and possibly be injured by so doing.
[Illustration: Fig. 28. Set-up on Warner & Swasey Turret Lathe for
Second Series of Operations on Forged Shrapnel Shell]
The average total time for making this piece complete is twenty-seven
minutes. On account of the rigidity of the tool support, the tools do
not require sharpening more often than once for fifty pieces, with the
possible exception of the cutting-off tool, which must be sharpened
after about half that number of pieces have been completed.
=Using Warner & Swasey Turret Lathe for Machining Forged Shrapnel
Shells.=--In Fig. 26 is shown a typical set-up on a Warner & Swasey
No. 2A universal hollow-hexagon turret lathe for machining an 18-pound
shrapnel shell forging. The arrangement of the various tools for
performing the first series of operations is more clearly illustrated
in Fig. 27, to which reference should now be made. The forging is
located for machining on a special arbor fitted into the spindle and
carrying two spring-controlled centering bushings _A_. These serve to
locate the shell, which is then gripped by the floating jaws of the
chuck on the external diameter, and a stop on the end of the arbor
locates the shell from the bottom of the powder pocket.
[Illustration: Fig. 29. Diagram Illustrating Sequence of Operations
performed at Second Chucking]
The first operation consists in taking a cut from the external
diameter with a special box-turner provided with a roll steadyrest
and carrying two turning tools. The second operation is handled from
the cross-slide, the shell forging meanwhile being supported by a
roll steadyrest clamped to the turret. In this operation the closed
end of the shell is faced with tool _C_, the corner rounded, and the
band groove formed with forming tool _D_. The third operation--first
chucking--is performed with tool _F_ which produces the waves in the
band groove, and is operated in the following manner: Referring to the
lower left-hand corner of the illustration, it will be seen that a
roll _G_ is brought in contact with the face-cam _B_, thus giving the
desired oscillating movement to the waving cutter. The fourth and final
operation consists in under-cutting the band groove with a tool clamped
to the turret. This tool gages from the end of the shell by a revolving
stop _H_, and is provided with two slides, set at the desired angle
to each other and the work, carrying under-cutting tools _I_ and _J_.
These slides are operated by handle _K_.
[Illustration: Fig. 30. Third Chucking Set-up on British Forged
Shrapnel Shell]
The second chucking on this shell is handled as shown in Figs. 28 and
29 on the same type of machine. As shown in Fig. 29, the shell for
this operation is gripped in an automatic chuck, and a stop _A_ for
locating it is held in the spindle. The first operation consists in
roughing out the powder pocket and diaphragm seat with a cutter _B_,
and rough-turning that portion of the shell held in the chuck in the
previous chucking with a tool _C_. This tool is held in the cross-slide
toolpost, and is controlled in its movement by a special guide fastened
to the regular taper-turning attachment. The second operation finishes
the powder pocket and diaphragm seat with a cutter _D_.
[Illustration: Fig. 31. Diagram Illustrating Relation of Tools for
performing Third Series of Operations]
[Illustration: Fig. 32. First Chucking on French Shell made from Bar
Stock on Warner & Swasey Turret Lathe]
After the second chucking, the shell is heated on the nose, closed
in and is then brought back to the turret lathe, when the operations
are performed as shown in Figs. 30 and 31. Here, again, the forging
is held in the automatic chuck and is located by a plug _A_ in the
spindle. The first series of operations consists in boring, facing
and chamfering the nose with a counterbore _B_, and at the same time
turning the external radius on the nose with a tool _C_. Tool _C_ is
held in the cross-slide square turret and is controlled in its movement
by a special guide fitting on the regular taper-turning attachment.
The second operation, shown to the left of the illustration, consists
in machining the radius inside the nose with a tool _E_, controlled
in its movement by the special guide _D_, as previously mentioned.
The third and final operation consists in cutting the thread with a
collapsible tap _F_.
[Illustration: Fig. 33. Second Chucking on French Shrapnel Shell]
=Using Warner & Swasey Turret Lathe for Machining Bar-stock Shrapnel
Shells.=--The method of machining shrapnel shells from bar stock
differs somewhat from that used for forgings, and is handled on a
No. 2A universal hollow-hexagon turret lathe. In this particular
case, the shell blank, previous to machining in the turret lathe, is
rough-drilled in a high-powered drilling machine to the bottom of the
powder pocket. Assuming that this has been accomplished, the operations
for the first chucking are then carried on as illustrated in Fig. 32.
Here the shell is held in an automatic chuck and is located by a stop
_A_. The first operation consists in counterboring the mouth with the
counterbore _B_, and rough-turning the external diameter with tool _C_;
second, counterboring with the cutter _D_ and turning further along the
shell with a tool _E_; third, finishing the bottom with a cutter _F_
and facing the end of the shell with a tool _G_.
[Illustration: Fig. 34. Third and Final Chucking on French Shrapnel
Shell]
In the second chucking, the operations shown in Fig. 33 are performed.
Here the shell is reversed in the automatic chuck and is located, as
before, by a stop _A_. The first operation consists in turning that
portion of the body held in the chuck in the previous chucking with a
roll-supporting turning tool _B_. Second, supporting the shell with a
roller support _C_ held on the turret, facing the end with a tool _D_,
and chamfering the band groove and the end with a cutter _E_ held on
the cross-slide square turret. The third operation is to support the
shell from the turret, knurling with a knurl _F_ from the cross-slide
square turret. Fourth, taper-turn from the end to the band groove with
a tool _G_, guided by the taper-turning attachment.
For the third chucking, the shell, as indicated in Fig. 34, is held in
the same manner as for the first chucking. First, it is recessed with
a tool _A_ and brought into action by operating the special holder
which has a cross-sliding movement; second, it is bored and faced
with a counterbore _B_ from the turret, and taper-turned with a tool
_C_ operated by a special guide from the taper-turning attachment. In
the third operation, the thread in the nose is rough-chased with a
tool _D_, controlled in its movement by the chasing attachment of the
machine; fourth, the thread is finished with a tap and tap-holder _E_.
[Illustration: Fig. 35. Diagram showing Method of holding and
performing First Series of Operations on Forged Shells on “Lo-swing”
Lathe]
=Machining Shrapnel Shell Forgings on the “Lo-swing” Lathe.=--By adding
a simple carriage to its “Lo-swing” lathe, the Fitchburg Machine Works,
Fitchburg, Mass., has adapted this machine for machining shrapnel
shells of different types. The following data and illustrations refer
particularly to tooling used for machining the Russian and French
shells. On the Russian shell, after centering, the forging _A_ is held
on a special arbor _B_ shown in Figs. 35 and 36. Placed over this arbor
is an expanding collar _C_, the inside surface of which is chamfered to
fit against surface _D_ on the stem of the arbor. The section of the
arbor next to the spindle is threaded and a large nut and handwheel
_E_ are turned to pull the sliding sleeve _C_ along the arbor and thus
expand it to firmly grip the inside of the shell forging. Sleeve _C_ is
connected to the nut _E_ by a threaded collar _F_. After the forging is
securely located on the arbor, which it should be understood extends to
the bottom of the powder pocket to gage it for length, the tail-center
_G_ is run in to support it.
[Illustration: Fig. 36. Set-up for performing First Series of
Operations on Russian Forged Shell on “Lo-swing” Lathe]
To those familiar with the “Lo-swing” lathe, it will be appreciated
that its chief efficiency lies in its system of multiple turning
tools. Thus, on this job, tools _H_, _I_, _J_, _K_, _L_, and _M_ are
all mounted on one slide, and in the illustration are shown in the
positions they occupy after taking their respective cuts. At the
beginning of the cut, turning tools _K_, _L_, and _M_ are drawn back
clear of the work to allow sufficient clearance for tools _H_ and _I_
to operate. With the tools drawn back and the carriage at the extreme
right of the bed, tool _H_ is the first to come in contact with the
work. This tool takes a roughing cut over the body of the forging,
finishing at the radius on the nose.
Tool _H_ is controlled in its action by a former pin on the tool-slide,
held in contact with the face of cam former _O_ by a stiff spring.
Former slide _O_ takes the place of the regular taper-turning former
ordinarily used on the “Lo-swing” lathe. When the former pin in the
slide carrying tool _H_ reaches point _P_ on former _O_, the tool is
withdrawn to conform with the shape shown at _N_ on the forging. The
tool is then fed in further toward the axis of the arbor, until the
former pin reaches point _Q_ on the slide, when the radius on the nose
is completed. Tool _H_ is the only one mounted on a taper-turning block.
[Illustration: Fig. 37. Diagram showing Method of performing Second
Series of Operations on Forged Shrapnel Shells on “Lo-swing” Lathe]
Just after tool _H_ passes point _N_, tool _I_ commences to cut at
the end of the forging, taking a finishing cut and ending up in the
position in which it is shown in the illustration. After tool _I_
reaches this position, the other tools _J_, _K_, _L_, and _M_ are
brought into action. Tools _K_, _L_, and _M_ are so situated on the
carriage that no lateral feeding is required. When these tools are in
action, the roller support _R_ takes the thrust. Tool _K_ roughs out
the band groove and is fed into the work by a handwheel. Tool _L_ cuts
the groove for attaching the brass case to the shell, and tool _M_,
carried on the same block, faces the end. Tools _K_, _L_, _M_, and _S_
are located on the same carriage and are fed in together. Tool _S_
rounds the corner of the shell. The carriage on which tools _K_, _L_,
_M_, and _S_ are located is now drawn back out of the way, and the
entire carriage moved over so that tool _J_ can be used to under-cut
the rifling band groove. After cutting off the center projection, the
first series of operations on the shell is completed.
[Illustration: Fig. 38. Set-up on “Lo-swing” Lathe for performing
Second Series of Operations on Russian Shell]
=Second Series of Operations on the Russian Shell.=--The second series
of operations is performed on the inside of the shell on the “Lo-swing”
lathe, which is provided with a special turret for this purpose. As
is shown in Figs. 37 and 38, the shell _A_ is held in special collet
jaws _B_ that have a two-point bearing on the shell. Stop _C_ in the
spindle locates the shell in the chuck. To manipulate the chuck for
tightening it on the work, handwheel _D_ is turned, carrying with it
the nut _E_ and ring _F_. Ring _F_ carries pins sliding in slots in
sleeve _H_ and driven into collet _B_, so that when nut _E_ is drawn
back it also carries collet _B_ into the taper in sleeve _H_, closing
the collet on the work. Turning handwheel _D_ in the opposite direction
releases the grip of the collet _B_ on the work. The first operation is
performed with tools _I_, _J_, _K_, and _L_. Tool _I_ bores the powder
pocket, tool _J_ roughs the diaphragm seat, tool _K_ rough-turns the
thread diameter at the shell mouth, and tool _L_ faces the end. The
turret is now indexed, and boring-bar carrying tool _M_ is brought
into operation. This tool turns the curved interior of the shell. To
accomplish this, the turret locking-pin is removed, allowing the turret
to float on its central axis. Fastened on the ways of the lathe at the
rear of the turret by a clamp _O_ is the cam bracket _N_ carrying the
guiding cam _P_. This cam, through pins _Q_ and _R_ in bracket _S_,
controls the float of the turret and guides the cutting tool _M_. In
the illustration, the tool is shown at the end of the cut. It will
also be noted that one surface of the cam is curved and the other is
straight; therefore, to compensate for this and also to steady the
turret, pin _R_ is backed up by a spring. Clamp _O_ is now released and
bracket _N_ moved back to allow the turret to be indexed. Bracket _N_
is located, when brought into the operating position, by a stop on the
bed of the lathe.
[Illustration: Fig. 39. Diagram showing Method of machining French
Shells on “Lo-swing” Lathe--First Series of Operations]
[Illustration: Fig. 40. Diagram showing Method of holding and applying
Tools on “Lo-swing” Lathe for performing Second Series of Operations on
French Shell]
In the third position, tool _R_ finishes the powder pocket, _S_ the
diaphragm seat, and _T_ the thread diameter, whereas _U_ acts as an
adjustable stop for the depth of the various tools. The fourth and last
operation is tapping with a collapsible tap _V_. This completes the
machining of the Russian shell on the “Lo-swing” lathe.
=Machining French Shrapnel Shell on “Lo-swing” Lathe.=--The machining
of the French shrapnel shell is well suited to the “Lo-swing” lathe.
A great many of the French shells are made from solid bar stock, and
when this is the case, the first operation, performed as shown in Fig.
39, consists in rough-drilling. If the shell is made from a forging,
this operation, of course, is dispensed with and the first tool used
carries boring and facing cutters, as shown at _A_, _B_, _C_, and _D_.
These rough-bore the three diameters on the inside of the shell and
face off the end to length. The next operation is accomplished with
two finishing boring tools _E_ and _F_, the depth of which is obtained
by an adjustable collar _G_ that comes against the produced with a
collapsible tap _H_. The turret is then indexed two holes, bringing the
special recessing tool into position. This tool is of the cross-slide
type and carries a back recessing cutter _I_. This completes the first
series of operations on the shell.
[Illustration: Fig. 41. Set-up on “Lo-swing” Lathe for performing
Second Series of Operations on Straight Type of French Shell]
=Second Series of Operations on Shell. French=--The second series of
operations on a French shell is accomplished as shown in Fig. 40. Here
the shell is held in the same manner as described in connection with
Fig. 35. The forging is placed on arbor _B_ that has an expanding
sleeve _C_ operated by the hand-clamping wheel nut _D_. Eight cutting
tools are located on the carriage. Tool _A_ turns the diameter at the
open end of the shell, _B_ the central part, _C_ cuts the band groove,
_D_ chamfers the section adjacent to the band groove, _E_ chamfers
the end of the shell, and _F_ knurls the band groove. Roll _G_, in
connection with roll _H_, supports the shell while the knurling is
being done, whereas tool _I_ faces off the end of the shell. At the
beginning of the cuts, tools _C_, _D_, _E_, and knurl _F_, also roll
_G_ and tool _I_, are withdrawn. This permits tool _A_ to cut the front
end of the shell at the beginning and finish the diameter at the open
end of the shell. Tool _B_ next comes into action and turns the central
part of the shell. Tool _C_ is then located in the correct position for
the band groove and the carriage on which tools _C_, _D_, and _E_ are
located is fed straight in, cutting the band groove and chamfering.
Knurl _F_ is then brought into position to knurl the groove, with roll
_G_ backing up the work against roll _H_. The last operation is to cut
off the center projection with tool _I_.
Fig. 41 shows the tool set-up on the “Lo-swing” lathe for machining
the straight type of French shell, in which two tool-blocks are used
for doing the straight turning. The leading tool turns the end of the
shell a little larger than the main body. The procedure for grooving,
knurling, and facing the shell is that previously described for the
forged shell, which is shown in Fig. 35. On the French shrapnel shell
the second operation follows directly after the first, whereas on
the Russian forged shell a nosing-in operation comes between the two
machining operations.
[Illustration: Figs. 42 and 43. Set-up and Tool Equipment on the
“Libby” Turret Lathe]
=Using the “Libby” Turret Lathe for Machining Shrapnel Shells.=--One of
the many ways of machining a shrapnel shell is illustrated in Figs. 42
and 43. This shows the set-up on the “Libby” turret lathe, manufactured
by the International Machine Tool Co., Indianapolis, Ind. In the first
chucking, the forging, as shown at _A_, is held on a special solid
arbor provided with a series of corrugations where it contacts with
the forging. This, in addition to providing a rigid support, assists
in gripping, and the shell is also gripped by a pair of chuck jaws
that act as drivers. First, a gang tool-holder carrying three stellite
turning tools _o_ is brought into position, and the cutting is
started, continuing for a distance of one-third of the length turned.
To provide additional support, a roller back-rest, carrying a facing
tool, is brought in to steady the work, and, as it is fed forward, the
end of the forging is faced off and chamfered.
[Illustration: Figs. 44. and 45. Machining Shrapnel Shell Forgings on a
22-inch Extra-heavy Turret Lathe]
The second operation on the first chucking is shown at _B_. Here the
cutter _a_ is brought in first and starts the band groove, after which
the under-cutting tool _b_ is brought in to under-cut the edges of
the groove. In the meantime, roller _c_ supports the work. Upon the
completion of the groove, the holder carrying cutter _d_ is advanced to
finish-face the end of the work and chamfer.
The third operation--cutting the waves in the band groove--is of an
interesting character and is accomplished as shown at _C_. A cam _e_
which is free to rotate with the work is first brought in contact with
it; then the cross-slide is advanced, carrying the waving tool _f_ and
the guide _g_. The guide _g_ fits in the cam groove and controls the
operation of the waving tool.
In the second chucking on the first operation the shell is reversed
in the chuck and is held in the manner indicated at _D_, Fig. 43. The
forging is located in the chuck by a stop-collar _h_, and is gripped on
the external diameter by the jaws of the chuck. A stepped boring tool
carrying five inserted blades is brought in to rough-bore the internal
diameters and machine the shell to the proper thickness at the bottom
of the powder pocket. This tool also carries a facing cutter that faces
off the shell to the proper length. While the boring tool is working,
a broad turning tool, held on the cross-slide, is brought in to bevel
the nose preparatory to closing-in. The next step is to taper-ream the
internal diameter, as shown at _E_. This completes the operations for
the second chucking.
The nose of the shell is now heated and closed in, after which the
third series of operations is performed. The first step in the third
chucking is to bore for the thread and face the end of the shell with
a turret tool, as shown at _F_. The next operation is to machine the
curved contour of the nose of the shell with a special turret tool
as shown at _G_. Here a wide forming cutter _i_, held in a turret
tool-holder, is brought in contact with the work, finishing the nose
of the shell to the proper form. During this operation, the shell is
supported by a roller in the holder.
The next operation is to form the inside of the nose of the shell to
the proper shape, as shown at _H_. This is accomplished with a forming
blade _j_, held in a holder clamped in the toolpost. Following this, a
collapsible tap is brought in from the turret to thread the nose of the
shell, as shown at _I_.
[Illustration: Fig. 46. Method of holding Shrapnel Shells for First
Operation on a 22-inch Turret Lathe]
=Machining Shrapnel Shells on a Heavy 22-inch Turret Lathe.=--Still
another method of machining shrapnel shells in a heavy turret lathe
is shown in Figs. 44 and 45. The shell being machined is an 18-pound
British shrapnel shell made from a forging. It is held on an expanding
arbor for the first operation, as shown in Fig. 46. The arbor is of
the three-point support type and is positive in its grip. Around the
periphery of the nose-piece are located three pinions _A_ capable of
being rotated by a square-ended wrench. These mesh with teeth in bevel
gear _B_ which, in turn, is threaded onto arbor _C_. The forward end of
this arbor is cone-shaped and operates the three gripping fingers in
the open end of the shell, whereas another rod passing through arbor
_C_ and connected to plunger _D_ operates, through the coil spring, the
three fingers used in gripping the shell by the powder pocket. This
arbor holds the shell securely while the machining operations are being
accomplished.
The first operation performed at the first chucking of the work is
shown at _C_ in Fig. 44. Here a turning tool-holder clamped to the
turret and carrying two cutters is advanced and takes a roughing cut
from the exterior diameter of the shell for practically its entire
length. The shell is supported by three roller supports as illustrated.
The second operation at the first chucking is performed from the
cross-slide, as shown at _D_. Here a forming tool of the tangent type
roughs out the rifling band groove, leaving sufficient metal in the
center for the production of the wave ribs. The third operation is
facing off the closed end of the shell from the turret as shown at
_E_, and the fourth operation consists in machining the waved ribs as
shown at _F_. The tool for accomplishing this operation is held on the
cross-slide and is operated from a face-cam on the nose of the spindle.
[Illustration: Fig. 47. Cutting Square Thread in Nose of French
Shrapnel Shell In “Automatic” Threading Lathe]
In the second chucking the shell is held in a three-jaw scroll chuck.
The first operation is to rough-bore the inside of the shell and powder
pocket with a tool _G_, Fig. 45, held in the turret; directly after
this a finishing tool of the same shape is brought in, finishing the
surfaces previously roughed out. The second operation is to face off
the open end of the shell and taper-form back of the nose from the
cross-slide, as shown at _H_, and at the same time turn that portion
of the exterior surface of the shell not machined in the previous
operation with a tool clamped to the turret as shown at _I_.
[Illustration: Fig. 48. Threading Base End of Bar-stock Shrapnel Shells
in “Automatic” Threading Lathe]
Previous to the third chucking, the nose of the shell is heated and
closed in. The shell is then held in a three-jaw scroll chuck provided
with special jaws. The first operation, as shown at _J_, consists
in boring and turning the nose of the shell with a tool held in the
turret. Following this, the hole is reamed with a standard reamer and
tapped with a collapsible tap. Both of these tools are held in the
turret, but are not shown in the illustration. This completes the
machining operations on the shell.
=Threading Shrapnel Shells on “Automatic” Threading
Lathes.=--Considerable difficulty has been experienced in cutting the
square thread in the nose of the French shrapnel shell. One method
which accomplishes this operation satisfactorily is shown in Fig. 47,
and is accomplished on a 12-inch “Automatic” threading lathe built by
the Automatic Machine Co., Bridgeport, Conn., and equipped with special
tools for this purpose. Referring to this illustration, it will be seen
that two tools are used--a roughing tool _A_, and a finishing tool _B_.
Tool _A_ roughs out the thread to a shape similar to the Acme type of
thread, whereas tool _B_ squares it up. The roughing and finishing
tools are held on the forward and rear carriages, respectively, and
are operated simultaneously, being advanced throughout the length of
the thread, withdrawn and returned to start a new cut. The method of
operating the tools is one of the chief features of the “Automatic”
threading lathe.
[Illustration: Fig. 49. Turning, facing, and threading Plugs for Closed
End of Bar-stock Shrapnel Shells in “Automatic” Threading Lathe]
The base end of shrapnel shells when made from bar stock is as a rule
bored out and a plug inserted to eliminate any piping effect in the
bar. Fig. 48 shows the method of accomplishing this operation on a
12-inch “Automatic” threading lathe. The work is held in a three-jaw
universal chuck and is supported by a roll steadyrest comprising two
rolls that are located beneath the work. On the extended end of the
rear roller stud is fastened a swinging stop that is used for locating
the base of the shell in the correct position ready for threading. The
base of the shell is counterbored in another machine, previous to the
threading operation. The threading is done with a circular tool held
on a special internal threading tool-holder, the latter being retained
in the toolpost carriage. The threading tool-holder can be moved
longitudinally to bring it into the proper relation to the work. It is
also held so that the cutting edge is turned upside down as this action
forces the work down in contact with the roller supports. By handling
the work in this manner, a steadyrest of the ordinary type is dispensed
with and the operation of the attachment facilitated.
[Illustration: Fig. 50. Grinding Shrapnel Shells on a Norton
Special-purpose Grinding Machine]
One method of making plugs for the base end of shrapnel shells when
made from bar stock is shown in Fig. 49. For this work, a 12 by 4
“Automatic” threading lathe equipped with special tools designed for
this purpose is used. The machine is provided with a draw-in collet
chuck that holds the rough-forged blank. The order of handling the
operations on this machine is to use the rear tool _A_ for turning
the external diameter of the plug. This is handled at the same rate of
feed as that required for threading, so that it is sometimes necessary
to take more than one cut, depending on the amount of material left on
the diameter. The vertical slide _B_ is for facing only and carries a
cutting tool _C_. This is supposed to finish the face in one cut, but
as the work will spring considerably, a light finishing cut is taken
when the tool is being drawn back from the center to the circumference
of the work. The threading tool _D_ is held on the front toolpost
and is of single-point construction. The feed given to this tool is
automatically controlled, both as to pitch and depth of cut at each
traverse.
[Illustration: Fig. 51. Diagram showing Scleroscope Hardness Test of
Heat-treated Shrapnel Shell at Various Points along its Surface]
In actual operation, both the threading and turning tools are in motion
all the time on the work, but the tools are independently controlled
so that either one can be operated separately. A stop is provided on
the back toolpost so as to turn each plug to the same diameter. The
automatic throw-out for the feed of the threading tool is set from the
front handle on the ratchet and pawl as regularly furnished on the
“Automatic” threading lathes.
=Grinding Shrapnel Shells.=--An increasingly large number of shrapnel
shell manufacturers are finishing the steel shell by grinding instead
of finish-turning. That is, the exterior surface of the shell is
rough-turned to within from 0.030 to 0.080 inch of the finished size
and is then finished to the required limits and shape by grinding,
as shown in Fig. 50. It is claimed by the advocates of grinding that
the finishing operations are more speedily performed in this manner
and that a more accurate and concentric shell is produced. They also
point out the fact that portions of the shell are so hard that it is
extremely difficult, if not impossible, to turn it in the allowable
time.
The varied heat-treatment given to the shell on the closed end and nose
leaves it harder in some sections than others, as indicated in Fig.
51. The section _E_, 2¹⁄₂ inches from the closed end of the shell,
must strike from 42 to 50 on the scleroscope, and the section _A_ at
the nose must strike between 20 and 25. The section marked _D_, or
that part of it to the left of the line that marks the limit of the
heat-treating on the closed end, has not been heat-treated at all, and
partly on this account, and also because of the gradually diminishing
thickness of the shell along this section, it strikes between 40 and
45, decreasing as the thickness of the wall diminishes, until at _C_
the section strikes but 35. Section _B_, adjacent to the annealed nose
of the shell, strikes about 30 on the scleroscope.
[Illustration: Fig. 52. Two-operation Method of grinding Shrapnel
Shells on Norton Grinding Machines]
On the other hand, some manufacturers are not putting the shell through
this heat-treating and tempering process, and omit the annealing and
machining of the nose after the nosing-in operation. This leaves the
nose with considerable stock to remove and in such a condition as
regards hardness that the grinding machine becomes a necessity. In
the face of these varying degrees of hardness of the shrapnel shell,
it will be seen that it is difficult to secure wheels of the right
grain and grade to suit all of these conditions. With this information
in mind, we can more intelligently take up the actual grinding of the
shell. The Norton Grinding Co., Worcester, Mass., has been actively
engaged in developing methods of grinding shrapnel shells and the
following illustrations and descriptions apply to this work.
[Illustration: Fig. 53. Three-operation Method of grinding Shrapnel
Shells on Norton Grinding Machines]
Fig. 52 shows the two-operation method of grinding the shrapnel shell.
Section _A_ at the open end of the shell is covered by a wide-faced
wheel formed to shape, that finishes the radius on the nose at one
in-feeding of the wheel. Sections _B_, _C_, and _D_ are covered by a
wide-faced wheel, formed to shape so as to finish these three surfaces
at one in-feeding of the wheel. Section _E_ at the closed end of the
shell is finished completely by turning.
Some manufacturers use a three-operation method of grinding the
shrapnel shell as illustrated in Fig. 53. In this case, the sections
_A_ and _D_ are first ground with the same wheel, as American
manufacturers deem it advisable to grind surface _A_ rather than
to finish it by turning. The second stage in this grinding is the
finishing of the nose _E_ with a formed wheel, and the third stage is
the finish-grinding of the body at points _B_ and _C_.
=Two-operation Method of Grinding Shrapnel Shells.=--The procedure
followed in grinding shrapnel shells by the two-operation method is
first to screw plugs into the open end of the shells, as shown in Fig.
52. The outer ends of these plugs are centered, and the projection
left on the closed end of the shell with the center intact acts as a
means of supporting the shell. Some of the Canadian manufacturers vary
this practice by cutting off the center projection on the closed end
of the shell and fitting a cap with a center hole over the closed end.
Others use a ball-bearing cup center to carry the closed end. American
manufacturers, however, leave the center projection on the shell until
after the grinding has been finished.
[Illustration: Fig. 54. Radius Wheel-truing Device for forming Grinding
Wheel for grinding Shrapnel Shell Nose]
In grinding the nose end of the shell, the amount of metal removed
varies from 0.020 to 0.090 inch on the diameter. The grinding wheel
operates at from 6000 to 6250 surface feet per minute. The speed of the
work is 75 revolutions per minute, or a surface speed of practically
75 feet, and the machine used is a Norton 6 by 32 plain grinder. The
wheel used is generally 14 inches in diameter by 2¹⁄₄-inch face. The
wheel requires truing for every five to twenty shells, depending upon
the amount of metal removed and the hardness of the shell. For truing,
a simple radius fixture carrying a diamond is used. Fig. 54 shows this
wheel-truing device clamped on the grinding machine bed. It is applied
in the same manner as the usual steadyrests used for supporting the
work. The diamond is mounted in a swinging arm that is operated by a
hand lever as shown. By successive cuts across the wheel, the desired
shape is attained.
[Illustration: Fig. 55. Norton Special Form Wheel-truing Device for
truing Wheel for grinding Shrapnel Shell Body]
For grinding the body either a 10 by 24 special-purpose or 10 by 36
Norton grinding machine is employed. The amount of metal removed
from the body varies from 0.030 to 0.075 inch on the diameter, and
the limits vary from 0.002 to 0.010 inch, depending largely on the
requirements of the plant in which the work is being done. The wheel
used on the body is 20 inches in diameter and is of the ring-wheel
type. It will be noticed in Fig. 52 that the wheel for grinding the
body is also formed to shape. The method of truing the wheel for
shaping the shrapnel shell body is shown in Fig. 55. This attachment
is clamped to the front of the grinding machine bed and at the top of
the bracket is fitted a slide _A_ operated by handwheel _B_. Upon the
face of this slide nearest the grinding wheel is pivoted an angular
arm _C_ that supports the diamond _D_ at its lower end. Under the end
of the upper arm is a spiral spring that keeps the diamond normally
back from the wheel. A plate former _E_ clamped to the bottom face of
the bracket is shaped to agree with the form to be given the wheel. At
the lower extremity of the arm and behind the diamond is mounted a roll
_F_ that bears constantly against form _E_. When the diamond slide is
reciprocated by turning the handwheel, the diamond is made to traverse
a path conforming with the cam that guides it. By moving the wheel in
toward the diamond and making successive traversings of the diamond,
the wheel is given the desired shape.
[Illustration: Fig. 56. Besly No. 14 Ring Wheel Grinder equipped for
grinding Shrapnel, but shown without Hoods and Water Attachments]
[Illustration: Fig. 57. Fixture used on Besly No. 14 Ring Wheel Grinder
for grinding Center End from Shrapnel Forgings]
For grinding the body, the wheel must be trued after every ten to
twenty-five shells are ground, depending upon the amount of metal
removed and the hardness of the shell. In grinding shrapnel shells, the
usual method is to fit a lot of the shells with the driving plugs and
carry them all through to completion before removing the plugs.
=Removing Center End From Shrapnel Forgings.=--For performing
practically all the machining operations on the shell, a center
projection is left on the closed end of the shell for supporting it.
This, of course, must be removed before the shell is completed. One
method of doing this is to use a Besly No. 14 ring-wheel grinder
equipped with a special fixture. A Besly grinder fitted up for this
work is shown in Fig. 56, and the fixture used for holding the shell
is shown in Fig. 57. The machine, as furnished, is arranged for wet
grinding, but is not so fitted up in the illustration. The fixture
is fastened to the geared lever feed table and is of simple design.
It is provided with a backing-up stop _A_, the work resting in two
semi-spherical groove projections on the fixture. The operator simply
holds the shrapnel shell in place by hand and then feeds it in against
the wheel and traverses it past in the usual manner. The time for
removing a ⁵⁄₈-inch diameter stub end projecting ³⁄₈ inch from the body
of the shell is less than a minute.
[Illustration: Fig. 58. Tools for making Base of Powder Cup]
[Illustration: Fig. 59. Tools for making Top Member of Powder Cup]
=Press Tools for Making Powder Cup.=--In the British shrapnel shell,
the powder in the base of the shell used for exploding it and ejecting
the lead bullets, etc., is held in a tin-plate powder cup. This is
completed in the punch press in the manner shown in Figs. 58 and 59,
and comprises two parts, a base and a top. The base is made from tin
plate 0.022 inch thick, whereas the top is made from 0.036 inch thick
tin plate. The bottom of the cup is completed in one operation with
the punch and die shown in Fig. 58, which is held in a single-action
press. It is turned out from a blank 3⁷⁄₃₂ inches in diameter and is
cut out and formed in one operation. The completed size is 2¹⁄₄ inches
diameter by ⁷⁄₈ inch high. After cupping, the top edge is trimmed in
a turret lathe. The press operations on the top, as shown in Fig. 59,
are a little more complex. The first operation consists in cutting
out a blank 2¹⁹⁄₃₂ inches in diameter. Then the edge is turned up with
another punch and die shown in the center of the illustration. The next
operation is piercing the center with the punch and die at the right,
and the last operation is drawing out a flange around the pierced hole.
The tools for this operation are shown to the extreme right, as is also
a completed powder cup. The final operation on the cup consists in
soldering the top to the base.
[Illustration: Fig. 60. Diagram illustrating “Twelve-punch” Method of
making Shrapnel Bullets from Lead Wire]
=Shrapnel Bullets.=--The most deadly and effective parts of a shrapnel
are the lead bullets which are held in the shell. When the timing fuse
explodes the powder in the base of the shell, the nose is blown off
and the bullets are thrown out in a cone shape. The range covered by
these bullets in the 18-pound shrapnel shell is about 250 square yards.
The lead bullets, which in most shrapnel are ¹⁄₂ inch in diameter, are
made from several different compositions, but consist chiefly of 87¹⁄₂
parts lead and 12¹⁄₂ parts antimony. The number of bullets carried in
shrapnel shells of the different governments varies. There are 252 in
the American 15-pound shell, and 235 or 236 in the British 15-pound
shell. The bullets used by the U. S. government have six flattened
sides, to facilitate packing, whereas those used by foreign governments
are spherical.
There are several methods of making shrapnel bullets. One is to cast
the bullets in iron molds, which are split in the center, so that the
bullet can be removed when cast. Another is to cut off slugs from lead
wire and strike these between dies in a heading machine. The bullet
heading machine takes the wire from a reel, cuts it off, forms it and
trims off the resultant flash automatically. In making the American
bullets, a second operation follows, consisting in flattening the
sides. The Waterbury Farrel Foundry & Machine Co. furnishes unit
equipments for doing this work. For the flattened bullets, the unit
consists of one hydraulic wire extruding press and fourteen heading
machines capable of giving a production of 850 bullets per minute. For
the spherical bullet, the unit equipment consists of one hydraulic
extruding press and eight heading machines, giving a production of 950
bullets per minute.
The method of casting lead bullets in ordinary molds is antiquated, and
another method somewhat similar to that just described has taken its
place. The first step is to produce the wire from which the bullets are
eventually made. This is accomplished in two ways. The first is the hot
metal process and consists in pouring the molten lead into a cylinder,
from which it is extruded through a die by a plunger advanced into the
cylinder. By this method, it is necessary to allow the metal to settle
before the press can operate. An improvement over this is utilized in
presses built by a hydraulic lead press manufacturer of Brooklyn, and
consists in first casting ingots of the required diameter and length
and then charging the press with these instead of pouring the molten
lead into the press chamber. Two presses have been designed for this
process. One has a capacity of 700 tons and is charged with ingots
weighing 150 pounds, whereas the other has a 900-ton capacity and is
charged with 200-pound ingots. The product from these two machines is
1800 pounds of lead wire from the small and 2500 pounds from the large
press per hour. The wire as it is extruded from the die is wound on a
reel carrying 2000 pounds of wire.
There are two principal types of swaging machines used for making these
lead bullets from wire. One carries a single set of dies, whereas the
other carries twelve sets of tools. The operation of the latter will
be described. Referring to the diagram, Fig. 60, twelve reels of lead
wire--not shown--are arranged in tandem on stands behind the press, six
reels in a row. The wire is conveyed from these reels to the dies by
a feeding mechanism, being guided to the individual tools by a plate
_A_, having twelve U-shaped impressions in its top edge. The wire now
passes over a spring _B_ which serves to lift it up slightly at each
stroke of the press. The tools _C_ and _D_, as shown, are provided
with half-spherical depressions in their adjacent faces and are set so
that they come within ¹⁄₆₄ inch of meeting. The dies are guided and
controlled in action by a special mechanism, and the press in which
they are carried operates at 70 revolutions per minute. This gives a
rated production of 840 bullets per minute. As is clearly indicated in
the illustration, considerable scrap is formed in making lead bullets
by this process--in fact the scrap is about 33 per cent of the reel of
wire; also owing to the setting of the punches a slight fin is formed
around the periphery of the bullet.
After forming, the bullets are taken to a tumbling machine where
they are tumbled for one hour. No other material is put into the
tumbling barrel, but the action of the bullets working on themselves
satisfactorily removes all the fins. Both the swaging and tumbling
operations must be carefully watched because of the necessity of having
the bullets a certain weight. The allowable variation on one pound of
bullets is one dram, and there are forty-one bullets to the pound. Ten
pounds of lead rod make 6¹⁄₂ pounds of bullets, and the scrap resulting
from the swaging operation is remelted and used over again. After
tumbling, the bullets are inspected and are then ready for use.