Deeds of a Great Railway / A record of the enterprise and achievements of the London and North-Western Railway company during the Great War

by G. R. S. Darroch

Ordinary engine lathes were eminently suitable for operations such as centring, rough and finished turning, grooving and external blending and turning copper bands. Then, thanks to the facility with which the various tools can be swung round in the lathe-turret and brought to bear on the work, turret-lathes were employed on operations such as rough and finished boring, internal blending, recessing and facing.

Rough turning on a fluted mandrel, rough and finished boring, and internal blending, in a concentric chuck secured to the face-plate of the lathe, are operations quickly disposed of.

"Blending," needless to say, produces in the mind an impression of smoothness and of harmony: smoothness unscored, that is, of the walls and base; harmony complete between the two, and indispensable.

Into the finished and concentric bore of our projectile is now forced a cleverly and home-designed expanding mandrel, a taper mandrel in fact, which expands a hollow (and again concentric) bush, and on this the base is centred. Transferred to an adjacent engine-lathe the shell is fixed on a shorter three-bush expanding mandrel, and turned to the correct and finished diameter. Removed to a turret-lathe, a slight operation of counter-boring the mouth is performed; this is necessary, as medical practitioners may be astonished to learn, for the purpose of receiving the nose. The mouth is also faced, and screwed, but screwing is effected on another instrument of torture, styled a thread-milling machine; so prior to lifting the shell from the turret-lathe a recess is cut in the far cavity of the mouth, this forming a clearance for the thread-milling tool. The turret of the lathe having no transverse travel, an ingenious little tool was designed and fixed into the turret-head by means of which a transverse travel, actuated by a hand-rachet and sufficient for the required depth of the recess, was obtained.

Anything which is at all conducive towards the saving of time, especially in war, is ipso facto a device of the utmost strategic and economic value. "Ask anything of me but time," once said Napoleon, "it is the one thing I cannot give you." So, in the case of our thread-milling machine, the saving of time effected is considerable. The shell is as incomplete without the screw-thread in its mouth, as it is without its nose; the thread has to be cut somehow; and by the employment of a milling-machine and thread-cutter the job can be done in about ten minutes as against an hour or more if done in an ordinary screw-cutting lathe.

Having recourse once again to an engine-lathe, we attach a "form" (or guide) plate to the slide-rest, to the profile of which the nose and shell-body together are blended externally. As we are now nearing completion, the next item on the programme is to see how we stand for weight, and in the event of the shell being a trifle on the heavy side, we either take a light cut off, reducing ever so slightly the diameter, or else we shorten the base. There remain now the base-plate and the copper band to complete the whole; the former is either screwed or slipped with a plain circumference into a recess in the base, riveted over with a compressed air riveter, and faced to the required thickness; the latter is pressed hydraulically into a groove, then turned and grooved to the required diameter. A kind of miniature Turkish bath now awaits the long-suffering object of our commiseration, in which it is steamed and cleaned, then placed nose downwards over a tank. In this unenviable position a stream of varnish is generously sprayed with a hand pump up its inside. Thereafter it reposes in an adjacent chamber or stove until the varnish is thoroughly dried and baked; whence emerging, a pneumatic tapping machine is waiting to clear the varnish from the thread of its nose. It is then "boarded" both in regard to weight and overall dimensions, and if passed "A1" by the inspector proceeds into bond, where it remains until "called up," "reporting" at a filling factory, and in due course being "drafted over-seas."

Prior to quitting the workshop's busy hum and reverting with our mind's eye to the "battle's magnificently stern array," where we may compare to further, if superficial, purpose the projectile and its mathematically proportioned features with the somewhat violent form of gymnastic exercise in which it is about to delight, a word or two in reference to the evolution of the copper band may not be held amiss, in view of the important rôle it plays relatively to the shell as a whole. The process by which these copper bands or discs were evolved was unique, and inasmuch as it was possible to effect a considerable economy by the evolution of three separate and distinct bands from one original sheet or square of copper, Crewe became responsible not only for the bands components of the 6-inch shell, on the manufacture of which she was exclusively concentrating her endeavours, but was able concurrently to produce for other firms further bands components of both 8-inch and 4·5-inch projectiles.

Equally with the fuse or gauge, the copper band ranks as one of those "particular components which are essential before you can complete the shell," and in order to preclude in so far as lay in his power to do so the possibility of any shortage of this particular component, Mr. Cooke put in hand and had completed within a fortnight from the date of commencement an entirely new hydraulic press having a capacity of 130 tons and a working pressure of 2000 lbs per square inch, by means of which copper cups were pressed out to approximately 700 per day, and from these cups were cut and turned bands of different diameters according to the size of shell for which they were required; the total number of copper bands thus manufactured at Crewe at the time of the Armistice being upwards of 700,000.

The method was simple when once evolved. The 8-inch band being of the largest diameter of the three was the first to be dealt with, then the 6-inch and finally the 4·5-inch. A piece of flat, square copper plate was first dished in the press by means of a solid punch, to the shape of a shallow bowl; annealed, it was pressed a little deeper; annealed again, the process was repeated a third time, but deeper still, the dish becoming a cup; and in order to obviate the drawback of the walls of the cup clinging to the circumference of the solid punch, a cleverly contrived split and collapsible punch was introduced, that is to say a punch which, on being pressed downwards, was expanded by a taper wedge to the full diameter required, and which, on being withdrawn, collapsed or shrank inwardly in proportion as the taper wedge preceded and automatically withdrew the expanded and circular sides, the latter disengaging simultaneously from the walls of the cup.

Transferred to the fitting shop, a band or disc 8-inch diameter was turned and cut off from the cup, the latter returning to the press, where through the medium of similar punches of requisite and correspondingly smaller diameters further operations resulted in the evolution of cups from which were turned 6-inch and 4·5-inch bands respectively and in sequence.