MAKING SHRAPNEL CARTRIDGE CASES
The brass cartridge case that contains the powder charge for propelling
the shrapnel shell from the bore of the quick-firing gun is drawn up
from a blank of sheet brass. The number of operations necessary to
complete the case depends on its size and the method of handling. Some
shell manufacturers prefer to do more or less drawing at one operation,
but in all cases the sequence of operations is practically the same.
The material used for shrapnel cartridge cases generally consists of
a composition of 2 parts copper and 1 part zinc. This alloy has been
found to possess the best physical qualities, that is, great tensile
strength and a high percentage of elongation when properly annealed.
The drawing operations through which the cartridge case passes increase
the hardness, and the ductility of the metal is restored by annealing.
The annealing temperature in most cases is from 1150 to 1200 degrees F.
On reaching this temperature, the work is either cooled off in water or
allowed to cool off gradually, as the speed of cooling does not affect
its physical qualities. In the following, two methods of handling the
various operations will be described.
=Method of Making Cartridge Cases.=--Figs. 1 and 2 show the sequence
of operations--blanking, cupping, re-drawing, indenting, trimming,
heading, and tapering, as advocated by the Waterbury Farrel Foundry &
Machine Co., Waterbury, Conn., for making cartridge cases for 18-pound
shrapnel. The first operation consists in cutting out a blank from
³⁄₈-inch sheet brass 6¹⁄₄ inches in diameter. The next operation is
cupping. This is handled in a short-stroke geared straight-sided press.
Before re-drawing, the cup is annealed, and the third operation, which
is handled in a longer stroke press, is then performed. Annealing
follows this operation, and then the fourth drawing or second
re-drawing operation is performed. This consists in reducing the
fillets slightly at the corners, decreasing the diameter of the cup to
4¹⁄₈ inches and increasing its length to 4¹⁄₂ inches. The dimensions
given here are approximate.
[Illustration: Figs. 1. and 2. Operations in making an “18-pound” Cartridge
Case]
=Indenting Operations.=--The fifth operation or first indenting
operation, which consists in indenting the bottom, is handled in a
press similar to that used for the cupping and re-drawing operations.
This shortens the length of the case by ¹⁄₄ inch and forces the
indentation about half way through the thickness of the stock. The
second indenting is then accomplished. This again shortens the case by
an additional ¹⁄₄ inch and squares up the corners. The case, without
annealing, is now passed through the third re-drawing, or seventh,
operation, reducing its diameter to 4 inches and increasing its length
to 5¹⁄₂ inches. It is annealed after this operation, and is then drawn
to a shape 8 inches in length by 3⁷⁄₈ inches in diameter, and the
wall decreased in thickness to ¹⁄₁₆ inch. The case is then annealed
and passes through the fifth re-drawing operation. The machine used
for handling the third, fourth and fifth re-draws is a long-stroke
straight-sided rack-and-pinion press. After the fifth re-drawing, or
ninth, operation, the case is trimmed and about two inches cut off
the end. This leaves the case in better condition for the succeeding
operations. The trimming machine is of the horizontal type.
=Final Re-drawing Operations.=--The sixth re-drawing, or eleventh,
operation is performed in a horizontal drawing press of the hydraulic
type provided with automatic reversing valves. This operation increases
the length of the case to 13¹⁄₄ inches and reduces its diameter to 3³⁄₄
inches. After this operation, the case is annealed and then 1¹⁄₄ inch
is trimmed off the open end. The thirteenth and fourteenth operations
consist in heading the case. These are practically of the same nature,
and combine to form the head of the case as shown in the illustration.
The heading operations each reduce the length of the case ¹⁄₄ inch,
and are performed in a 1000-ton hydraulic heading press operated by a
geared compound power pump and having a working pressure of 5600 pounds
per square inch on the ram. After heading, the case is annealed and the
fifteenth operation, which consists of tapering, is performed. The
first tapering, or fifteenth, operation reduces the mouth of the case
to 3⁹⁄₁₆ inches in diameter and gradually tapers it for a distance of
5⁷⁄₈ inches--half the length. The case is then annealed, pickled and
washed, and a second tapering operation is performed. This reduces the
mouth of the case to 3³⁄₈ inches and tapers it completely to the head.
The case is not annealed after the last tapering operation, but ¹⁄₄
inch is trimmed off the end.
The various operations through which a cartridge case passes in drawing
and forming to the correct length having been described, attention will
now be given to the type of tools used for this purpose. These tools
have been designed and built by the Ferracute Machine Co., Bridgeton,
N. J., and are used with its presses for making cases for 3-inch
projectiles.
=Cupping and First Series of Re-drawing Tools.=--The cutting out of
the blank is frequently omitted because the specified thickness and
size can be furnished by the mill. Before cupping, the dies and blanks
are well greased, as this assists in drawing. Olive oil or soapy water
is used, depending on the stage at which the drawing operations have
arrived. The first cupping operation is accomplished with a punch and
die as shown at _A_ in Fig. 3. This operation is accomplished in a
Ferracute 100-ton ram press equipped with a dial feed. The die consists
of a hardened ring of tempered steel having an interior shape similar
to a truncated cone. The punch is slightly tapered on the lower end and
has an air vent hole drilled up through it to facilitate the drawing
and produce a cup free from wrinkles.
[Illustration: Fig. 3. Tools for drawing a 3-inch Shrapnel Cartridge
Case--Ferracute Machine Co.’s Method]
The second operation, or first re-drawing operation, is shown at _B_.
Here the type of die used differs somewhat from that shown at _A_, in
that the drawing angle is 15 instead of 45 degrees. The cup, after this
operation, is reduced in diameter to 3.877 inches and is 2⁷⁄₈ inches
long. After the first cupping operation, the case is annealed.
The second re-drawing operation is accomplished as shown at _C_. The
die in this case is the same as at _B_, as is also the punch, except
for an increase in the taper and change in shape on the end. The
object of this, of course, is to keep the case thick at the head but
reduce the walls further up along the section. The case, after this
operation, is also drawn out to a length sufficient to necessitate
using a stripping device for removing it from the punch. This is
accomplished by six spring-operated stripper pins as shown, which
slip over the top edge of the case as it is forced through the die,
stripping it from the punch. The cup now passes through the third
annealing operation and is ready for the third re-draw, shown at
_D_. The press used for performing this operation is similar to that
described, and the die and punch is similar in construction to that
shown at _C_.
=Final Re-drawing Operations.=--For the final re-drawing operations,
horizontal double-ended screw presses instead of the horizontal
hydraulic presses formerly used are employed. Horizontal presses are
used because the length to which the cartridge case is drawn after
the third re-draw is such that it exceeds the stroke of the vertical
presses. The cartridge case, after each drawing operation, is annealed;
_E_ in Fig. 3 shows the fourth re-drawing tools, which are handled in a
horizontal screw press. The die used is similar in shape to that shown
at _D_, but the holder in which it is held differs, of course, owing
to the difference in the type of press used. The stripping arrangement
for removing the case from the punch is also of a different type. In
this case five spring-operated stripper pins are held in a holder which
is free to oscillate within certain limits in the block in which it
is retained. The reason for having this oscillating stripper is that
it accommodates itself to the irregular shape on the end of the case
and gives practically a constant pressure all around the circumference
of the case, assisting in removing it from the punch. The case is now
annealed and is finish-drawn as shown at _F_. Here the same type of
die, stripper arrangement, etc., is used as that shown at _E_. The case
in the fifth re-drawing operation is 14³⁄₈ inches long by 3.186 inches
outside diameter.
=Annealing and Washing Cartridge Cases.=--As was previously stated,
the cartridge case, after practically every re-drawing operation,
is annealed, being subjected to a temperature of about 1150 to 1200
degrees F. and then allowed to cool off or dipped in water which, of
course, forms a scale on the surface of the case. This must be removed
before any subsequent operations can take place. Several different
solutions are used for this purpose, but a common one comprises the
following: Sulphuric acid diluted with water to a strength of 1 to 4.
This pickling solution is held in lead-lined wooden troughs and the
case is allowed to remain in the bath varying from eight to fifteen
minutes, according to the strength of the solution. The cases are then
washed in lead-lined wooden troughs through which a stream of water is
circulated to remove all traces of the acid.
[Illustration: Fig. 4. Fixture for testing Hardness of Cartridge Cases
with Shore Scleroscope]
=Testing Hardness of Cartridge Cases.=--The hardness of a cartridge
case must conform to a certain standard. When too soft, a permanent
set will occur from the pressure of the firing charge and the case
will stick in the breech of the gun. When the hardness is too high for
a given composition of brass, it is too brittle and will split, or
the head may blow off. There is, therefore, a certain hardness which
must be adhered to as closely as possible. Some manufacturers hold the
standard to within 20 to 25 on the body walls and reject cases striking
15 as being too soft, and 30 to 35 as being too hard.
Owing to the thinness of the walls of the case, it is impossible to
take a reading without rigidly supporting it, and for this purpose the
Shore Instrument & Mfg. Co., 551-557 West 22nd St., New York City,
has devised a special fixture as indicated in Fig. 4. This comprises
a bracket _A_ held in an ordinary vise, to which is fastened an anvil
plug _B_, as indicated. In order to hold the case tightly against the
anvil plug, a spring _C_, fastened to the bracket _A_, is also fastened
to a yoke _D_ surrounding the case. A rod attached to the yoke and to
a foot treadle furnishes a means of drawing the yoke down to hold the
case in contact with the plug. The anvil plug provides the weight or
inertia to resist the impact of the drop-hammer of the scleroscope, but
in order to be sure that there is proper contact of the case with the
plug a rubber cushion _E_ is provided between the pressure ring or yoke
and the brass case.
[Illustration: Fig. 5. Special Shrapnel Case Trimming, Facing, and
Chamfering Machine]
[Illustration: Fig. 6. Sequence of Operations performed on Cartridge
Case in Machine shown in Fig. 5]
=Machining Shrapnel Cartridge Cases.=--The Bullard Machine Tool Co.,
Bridgeport, Conn., has designed and built a number of special machines
for performing the machining work on the head and mouth ends of brass
cartridge cases. This machine, as will be seen from Fig. 5, is of the
hand turret machine type, designed to work on the case from both ends.
In this machine the brass case is chucked in the center of an extremely
large spindle, and worked on from the head end with four sets of turret
tools and two sets of cross-slide tools, while the mouth end is bored
and trimmed with tools held on a carriage located on the back facing
bar. The drive for the work chuck spindle is over a 16-inch pulley
with a 3-inch belt. The pull of the belt is not taken directly on
the spindle, but on a special pulley bearing 7³⁄₈ inches in diameter
and 5 inches in width. The spindle itself is supported in bearings 9
inches in length and 5⁷⁄₈ inches in diameter. As previously mentioned,
the spindle is hollow so that any type of shrapnel cartridge case up
to 4¹⁄₄ inches in diameter and from 10 to 18 inches in length can be
machined.
[Illustration: Fig. 7. Set-up showing First Operation on Cartridge Case
Head]
From the construction of the machine in Fig. 5 it will be seen that the
front end of the spindle carries a large three-jaw chuck of special
design. These jaws catch the cartridge case just under the head and
revolve it for machining. The case is supported internally by a tubular
arbor which also acts as a stop and is attached to a rod extending to
the rear bracket where it is backed up by a spring. The front end of
this tubular support or stop is provided with a thrust ball-bearing so
that the case can be loaded in the chuck while the spindle is running.
When the chuck operating lever is manipulated to close the chuck jaws
on the work, it first draws back the rod mentioned through the medium
of a tie-rod and the rear bracket to a positive stop, and then closes
the jaws on the work. The cartridge case is put in and removed from the
chuck with the turret indexed between stations to give the required
space.
[Illustration: Fig. 8. Set-up showing Fourth Operation on Cartridge
Case Head]
[Illustration: Fig. 9. Set-up showing Operations on Mouth End of Case]
The back boring and trimming head is held on a hollow spindle through
the center of which the rod passes. This spindle is provided with rack
teeth on its top surface which engage with a pinion located in the
extension bracket and operated by a handle. The forward position of the
boring and trimming head is governed by a stop-collar.
[Illustration: Fig. 10. Set-up showing Sixth Operation on Head End of
Case]
[Illustration: Fig. 11. Set-up showing Seventh Operation on Head End of
Case]
=Sequence of Machining Operations on Cartridge Case.=--The sequence
of machining operations performed on the cartridge case in this
machine is shown diagrammatically in Fig. 6, and also in Figs. 7 to 11,
inclusive. Referring to Figs. 6 and 7, the first operation consists
in rough-drilling and counterboring the hole in the head of the case
with combination tool _A_. The second operation (see Fig. 6) consists
in facing, trimming and chamfering the head with tools _B_, _C_, and
_D_ held on the front of the cross-slide. The third operation is to
finish chamfering and facing the head of the case with tool _E_ on the
rear of the cross-slide. The fourth operation consists in under-cutting
the primer seat with the tool _F_ which works on a turret slide and is
operated by lever _G_ as shown in Fig. 8.
[Illustration: Fig. 12. Diagram showing Method of chucking a French
75-millimeter Cartridge Case on a Potter & Johnston Chucking Machine]
[Illustration: Fig. 13. Diagram illustrating Machining Operations on
French Cartridge Case on Potter & Johnston Machine]
The following operations are now performed on the mouth or open end of
the cartridge case as shown in Figs. 6 and 9, with the spindle running
at the same speed--500 R. P. M.--as that used for the first series of
operations. Two tools _H_ and _I_ are used. Tool _H_ bores the mouth
of the case for a distance of 1 inch, whereas tool _I_ trims off the
open end of the case and rounds the edges. The mouth of the case at the
rear end of the spindle is supported by a hardened bushing to prevent
it springing away from the action of the boring tool. The boring and
trimming tools are mounted in a special head _J_, Fig. 9, that is
operated back and forth by a handle _K_ through the medium of a rack
and pinion. The forward movement of this head, as previously explained,
is controlled by means of an adjustable collar _L_ screwed onto spindle
_M_.
[Illustration: Fig. 14. Tooling Set-up for Machining 18-pound Cartridge
Case]
The work-spindle is now slowed down and the following operations,
shown in Figs. 6, 10, and 11, are performed on the head end of the
case. The sixth operation is to finish-counterbore and ream the primer
pocket with tool _O_ held in an adjustable holder, whereas the seventh
operation is threading the primer pocket with collapsible tap _P_. The
chuck lever in Fig. 5 is now manipulated, first, releasing the grip of
the chuck jaws on the case and, second, advancing the rod to eject the
case sufficiently to enable it to be easily removed from the chuck. The
spindle is changed to the highest speed after the next case is put in.
In changing the work, it is not necessary to stop the spindle.
[Illustration: Fig. 15. Tool Set-up for Machining 18-pound Cartridge
Case]
=Machining Shrapnel Cartridge Cases on Potter & Johnston
Automatics.=--The cartridge case is made from sheet brass as previously
stated. It is practically formed to shape in drawing and heading
machines, but to secure the desired accuracy on the head and primer
pocket these surfaces are machined. The method of holding the French
75-millimeter case on a No. 5A Potter & Johnston automatic chucking and
turning machine for machining the head and primer pocket is shown in
Fig. 12. Here it will be seen that the cartridge case butts up against
a stop _B_ and fits over the tapered plug _C_, which steadies it. It
is held in place by an ordinary draw-in collet _D_. This is operated
by means of a lever _E_, fulcrumed to a bracket on the rear end of the
machine and operating a sliding clutch collar. The chuck is operated
through fingers which draw back the sliding sleeve to which it is
attached. These fingers operate against a spring at the rear of the
spindle which serve to open the collet.
The machining operations on the French shrapnel cartridge case are
handled in the manner illustrated in Fig. 13. The first operation is to
rough-drill the hole in the head. The turret is then indexed, bringing
in a roughing reamer which reams the hole previously drilled, whereas
the front cross-slide carries tool _B_ that faces the head and a
circular tool _C_ that rough-forms the external diameters of the head.
Upon the next indexing of the turret, the tool _D_ counterbores the
powder pocket and the circular forming tool _E_ finish-forms and
rough-chamfers the head. The last operation consists in finishing the
primer pocket with a taper reamer _F_.
=Machining the British Shrapnel Cartridge Case.=--The brass cartridge
case for the British shrapnel is more difficult to machine than the
French case, as reference to Figs. 14 and 15 will clearly show. The
machining operations are accomplished on a No. 5A Potter & Johnston
automatic chucking and turning machine having a five-sided turret. The
first operation is to drill the primer pocket hole with a three-step
drill _A_. The turret is now indexed and the surfaces previously
roughed out are finished with inserted-blade counterbore _B_. At the
same time, the head of the case is faced with a relieving tool _C_ held
on the cross-slide and rough-formed with circular tool _D_.
The turret, in being indexed to the third position, brings vertical
recessing tool _E_ into operation. This carries two cutters, one of
which recesses the primer pocket at the point where the thread is to
terminate, whereas the other removes the burr and faces the inner boss.
In the fourth operation, the smallest diameter of the primer pocket
is reamed and the largest diameter of the hole chamfered by tools
held in bar _F_. The rear cross-slide is advanced at the same time,
carrying the circular tool _G_ that finish-forms the head. The final
operation--threading--is performed with the “Geometric” collapsible tap
_H_.
DRAWING, HEADING AND MACHINING OPERATIONS ON “18-POUND” BRITISH
CARTRIDGE CASE
[Illustration]
+-----------------------+-------+-------+-----------+---------------+
| | Dimensions | | |
| Operation* | Inches | Machine | Scleroscope |
| | A | B | Used | Reading |
+-------+---------------+-------+-------+-----------+---------------+
| 1 | Blanking | | | Punch | 15 |
| | | | | Press | |
| | | | | | |
| 2(300)| Cupping | 4.45 | 2.30 | Bulldozer | _a_, 15; |
| | | | | | _b_, 50 |
| | | | | | |
| 3(300)| Annealing | | | | 15 |
| | | | | | |
| 4(300)| 1st Redrawing | 4.232 | 3.45 | Bulldozer | _a_, 15; |
| | | | | | _b_, 50 |
| | | | | | |
| 5(300)| Annealing | | | | 15 |
| | | | | | |
| 6(300)| 2nd Redrawing | 4.081 | 4.6 | Bulldozer | _a_, 40; |
| | | | | | _b_, 45 |
| | | | | | |
| 7(300)| Annealing | | | | 15 |
| | | | | | |
| 8(300)| 1st Indenting | 4.081 | 4.23 | Bulldozer | _a_, 18; |
| | | | | | _b_, 15 |
| | | | | | |
| 9(300)| 3rd Redrawing | 3.952 | 6.25 | Bulldozer | _a_, 18; |
| | | | | | _b_, 45 |
| | | | | | |
|10(300)| Annealing | | | | _a_, 13; |
| | | | | | _b_, 15 |
| | | | | | |
|11(300)| 4th Redrawing | 3.844 | 7 | Bulldozer | _a_, 35; |
| | | | | | _b_, 45 |
| | | | | | |
|12(300)| Annealing | | | | 15 |
| | | | | | |
|13(300)| 2nd Indenting | 3.844 | 6.875 | Bulldozer | _a_, 18; |
| | | | | | _b_, 15 |
| | | | | | |
|14(175)| Drill Hole in | | | Vertical | |
| | Primer Pocket | | | Drilling | |
| | | | | Machine | |
| | | | | | |
|15(200)| Trimming | 3.844 | 6.25 | Toledo | |
| | and Burring | | | Trimmer | |
| | | | | | |
|16(180)| 5th Redrawing | 3.789 | 9.75 | Frog and | _a_, 20; |
| | | | | Switch | _b_, 40 |
| | | | | Planer | |
| | | | | | |
|17(300)| Annealing | | | | _a_, 20; |
| | | | | | _b_, 16 |
| | | | | | |
|18(180)| 6th Redrawing | 3.738 | 13.35 | Frog and | _a_, 20; |
| | | | | Switch | _b_, 45 |
| | | | | Planer | |
| | | | | | |
|19(200)| Trimming | 3.738 | 11.875| Toledo | |
| | | | | Trimmer | |
| | | | | | |
|20(100)| Heading | 3.738 | 11.750| 350 ton, | _a_, 40 to 50;|
| | | | | C. P. R. | _b_, 50 |
| | | | | Hydr. | |
| | | | | Press | |
| | | | | | |
|21(180)| Annealing | | | | _a_, 40 to 50;|
| | Mouth | | | | _b_, 25 to 35 |
| | | | | | |
|22(300)| 1st Tapering | 3.347 | 11.875| Bulldozer | _a_, 40 to 50;|
| | | | | | _b_, 35 to 40 |
| | | | | | |
|23(300)| 2nd Tapering | 3.328 | 11.95 | Bulldozer | _a_, 40 to 50;|
| | | | | | _b_, 35 to 45 |
| | | | | | |
|24(40) | Machining | | | Bullard | |
| | Mouth and | | | Case | |
| | Head | | | Machine | |
| | | | | | |
|25(80) | Hand Tapping | | | Bench | |
| | | | | Fixture | |
| | | | | | |
|26(80) | Reaming | | | Bench | |
| | | | | Fixture | |
| | | | | | |
|27(80) | Inspecting | | | Various | |
| | | | | Gages | |
| | | | | | |
|28(80) | Stamping | | | | |
+-------+---------------+-------+-------+-----------+---------------+
* Number in brackets indicates Production Per Hour.
Operations: Supplementary Information
Lubricants Cupping, Redrawing and Indenting Viscocity
Tapering Dry
Machining Mouth and Head Mystic
Annealing Process (except Mouth) Oil Furnace--1100 to 1140 °F
Water Cooling and Acid Wash
Annealing Process (Mouth) Oil Burner--800 °F
Cool in Air
=Summary of Operations on Cartridge Cases.=--The accompanying table
gives a summary of the cupping, drawing, annealing, indenting,
trimming, heading and machining operations on a British 18-pound
cartridge case of a composition of 70 parts electrolytic copper and 30
parts Bertha spelter. In the plant where this information was obtained,
the cupping, indenting, and first, second, third, and fourth re-drawing
operations are accomplished on bulldozers, while the fifth and sixth
re-drawing operations are accomplished on a frog and switch planer from
which the cross-head has been removed and a special fixture substituted
in its place. The punch is held rigidly in this fixture and the die on
another fixture clamped to the table of the planer. Practically the
same condition prevails on bulldozers. Here the punch is held rigidly,
whereas the die is held in the traveling slide. As a lubricant for
drawing a compound known as “viscosity,” manufactured by the Cataract
Refining Co., is used throughout, except on the fourth and fifth
re-drawing operations, where ordinary commercial vaseline has been
found to give the best results.
The annealing is done in a Quigley oil furnace, which is kept at a
constant temperature of between 1100 and 1140 degrees F. The cups are
handled in sheet-iron boxes with wire bottoms carrying 140 cups. This
furnace holds seven of these boxes; it requires 35 minutes for one lot
of cups to pass completely through the furnace. In other words, a box
is put in and taken out every five minutes, thus giving an annealing
time of thirty-five minutes on each batch. After dipping in water, the
cups are immersed in a weak solution of sulphuric acid to remove all
scale.
Scleroscope readings are taken before and after each drawing operation,
so as to ascertain whether the metal is being properly annealed or
not. The blank also is tested with a scleroscope before any work is
done on it, and should strike 15. The head of the shell must strike
between 40 and 50, being softer at the center than at the rim. The
readings are taken on four radii on the head, and at intervals of ¹⁄₈
to ³⁄₁₆ inch apart. In heading, considerable difficulty was at first
experienced in securing the correct scleroscope readings. Instead of
the head being harder at the rim than at the center, the reverse was
the case. It was found that the metal in flowing towards the center
packed up to such an extent that the case was made considerably harder
at this point. A method which overcame this difficulty consisted in
drilling a ¹⁄₄-inch hole down through the primer pocket previous to the
heading operation. This allowed the metal to flow towards the center of
the head with comparatively little resistance, and hence the correct
hardness was obtained at the rim, as well as in the center of the head.
The machining of the head and mouth is accomplished in Bullard special
cartridge case trimming machines of the double-ended type, that is,
one set of tools are located in one end for machining the mouth and
another set of tools held in the turret and on the cross-slide for
machining the head and primer pocket. Following this, hand-reaming
and hand-tapping operations are accomplished so as to get the desired
accuracy and fit in the primer pocket. Inspecting and stamping
operations finish the principal operations on the cartridge case.