The walls of the case are thin, thereby expanding against the walls of the breech of the gun, and preventing any escape of the propellent gases; and for the purpose of easy extraction they (the walls of the case) are slightly tapered to within about 1/2 inch of the mouth which fits parallel over the end of the shell.
Rolling out Dents in 4·5-inch Fired Cartridge Case.
[To face p. 89.
Upon receiving a returned, or fired, cartridge case in the Works, the primer is first of all removed, then the case is boiled in a solution of caustic soda for the purpose of removing grease and dirt. What is known as a "hardness" test follows next in order of sequence, this to determine whether the metal of the case is still good for further service, and is performed by a little instrument known as a sclerometer (derived, as our classical contemporaries will tell us, from the Greek word (σκλήρος, hard), consisting of a tube marked with a graduated scale down which a tiny metal ball is dropped on to the side of the case; the ball should rebound to a point on the scale approximating a height of two inches, anything below this proving that the metal has become too soft for further use, when the case is accordingly scrapped. The cases which show a requisite degree of hardness are then annealed or suitably tempered round the mouth, this process ensuring a subsequent loose fit round the end of the shell.
Rolling the mouth to internal limit gauges is effected by means of a specially improvised apparatus rigged up on the bed of an engine lathe, consisting of two fixed housings inside which runs a belt-driven sleeve bored to the correct taper of the cartridge case, and in which the latter is carried. A duplex ball-bearing roller running on a central spindle secured in a pad fixed to a cross-slide, and operated transversely by a pedal, applies pressure against the walls of the cartridge case, the dents and bruises being thus gently removed and an even surface obtained.
It should be borne in mind that the entire process of repairing these cartridge cases (with the exception of brazing by coppersmiths with an acetylene flame any cracks or splits which already existed or became apparent in the repairing operations) was carried out by female labour working three eight-hour shifts, and one of the neatest of the diverse mechanical requisites which the girls were called upon to operate and which was the immediate outcome of managerial forethought and ingenuity was an adaptation of an hydraulic press for the purpose of correctly reforming the taper walls of the cartridge case to the true form of the gun chamber or breech. A cast-iron block with recesses cored in (in which are fitted a rocking lever pivoted in the centre, and two hardened cast-steel dies, one on either side) repose on rolling bearings arranged on the bed of the press.
At each end of the rocking lever is attached an adjustable ejector ram acting centrally inside the cast-steel dies, which latter are bored taper to the required shape of the cartridge case. Upon inserting a cartridge case in each die, the cast-iron block is pushed transversely by hand across the bed of the press, bringing one of the cases central with the ram, which, when applied, forces the case home into the die, thereby pressing and reforming the walls to their true and original shape. The ram being withdrawn, the cast-iron block is pulled back so that the second cartridge case in its turn comes central with the ram and the effect of pressing it home in its own particular die is to push back the pivoted arm, the other end of which, advancing automatically, expels the previous and finished case; cartridge cases being inserted and ejected in this manner ad infinitum.
The cast-steel dies naturally become affected by constant use, more especially on the protruding shoulder against which the thickest part of the case (viz. where the walls rounded into the base) is pressed, this necessitating the shoulder being re-radiused perhaps every fortnight, and a slight readjustment of the die in the block.