December 15, 1892] 



NA TURE 



63 



THE MAKING OF RIFLES. 



A T a recent meeting of the Institution of Civil Engineers, Mr. 

 ■'^ John Rigby, superinlenilent, Enfield Factory, read an in- 

 teresting paper on the manufacture of small arms. We repro- 

 duce from the abstract printed for the Institution Mr. Rigby's 

 lucid account of the various processes of manufacture of the 

 components of the Lee-Metford Ntark I. magazine-rifle, of 0*303 

 inch bore, the weapon adopted for ihe British Army — an ac- 

 count which he prefaced with a general description of the Enfield 

 Factory. 



The most important part of a rifle was the barrel, which had 

 always engaged the special attention of gun-makers. Up to the 

 time of the Crimean War, it was, for the bulk of British troops, 

 a comparatively rude tube of iron, lap-welded under rolls and 

 tapering externally, with a cylindrical bore of about \ inch 

 diameter. The barrel of the present day was a steel tube of 

 accurate workmanship, only yV inch bore, almost perfectly true 

 and straight, rifled to ^T.^uiyinch, and so closely inspected that the 

 existence of the most minute grey or seam in the bore, requiring a 

 highly-practised eye to detect it, was sufficient to condemn it. 

 The material used was produced either by the Siemens- Martin or 

 the crucible process of manufacture, and was supplied to Enfield 

 as a solid round bar \% inch diameter and 15^ inches long. After 

 severe testing, this bar was passed through a rolling-mill to draw 

 it to its full length : it was then taken to the forge, the swell at 

 the breech-end was stamped to the required shape by a steam- 

 hammer, and afterwards straightened cold. The next step was 

 to submit the bar, without annealing, to the turning and 

 drilling-machines. The latter were horizontal, the drills operating 

 from each end. In the process of drilling, the barrel revolved 

 at nearly r,ooo revolutions a minute against half-round bits held 

 flat down, a capillary tube, of brass, supplying a soap-and-oil 

 emulsion, at a pressure of 80 lb. to the square inch, to wash out 

 the swarth and cool the cutting-edge. The drills advancing from 

 each end continued boring until a small disk about yJtt inch 

 diameter broke out, and the two holes met. The tendency 

 of the drills to follow the line of axis of a revolving bar was 

 one of those curious occurrences in practical mechanics which 

 might be accounted for after observation, but which no one 

 would predict. Occasionally, through some defect in the steel, 

 a drill wandered from the axial line ; in this case the barrel was 

 taken from the machine and reset sufficiently to bring the hole 

 true again. To test its truth, a ray of light was made to 

 illuminate the flat bottom of the hole while the barrel slowly 

 revolved. It was very rarely that a barrel was rendered waste 

 from bad drilling. Rough-boring followed with a three-edged 

 bit, the blade being about 4 inches long. The rough external 

 turning was effected in self-acting lathes, which gave the required 

 ■ curved taper. Three or four cutters acted simultaneously, 

 each producing a long cutting that attested the quality of the 

 metal of the barrel. The operation of barrel-setting followed. 

 Previous to rough-turning, the barrels were fairly straight 

 internally, but the removal of the metal caused slight in- 

 equalities which were te>ted by the eye of the barrel-setter, and 

 corrected by transverse blows. This constituted skilled labour 

 of a peculiar character, and was performed by young men of 

 good sight, who were specially trained for the purpose. After 

 middle life the eye generally lost some of the quality necessary 

 for this work, and it was rare to find a man excel in it after 

 that period. Many mechanical devices had been contrived to 

 supersede the simple ray of light laid, as if it were a straight edge, 

 along the surface of the bore ; but the eye still remained the 

 arbiter of straightness and could be relied on for very accurate 

 results. The construction of the barrel was completed by the 

 important operation of rifling. In British small-arm factories 

 the system was followed of planing out each groove separately 

 with a hooked cutter, and had been brought almost to perfection. 

 In Continental and American factories the grooves were ploughed 

 out by cutters, with several cutting or knife-edges set at an angle 

 and following one another in the manner of a single-cut file or 

 float. Similar machines had been tried at Enfield, but did not 

 give as smooth a cut as the slower-moving, single-tooth machines. 

 A few passes of a lead lap, fed with fine emery, removed any 

 burr that might remain, and completed the polish ; a cylindri- 

 cal lap, spinning rapidly, was then passed through, and gave the 

 final finish to the barrels. The limits of gauging were from 

 0-303 to 0-305 inch. 



Next in importance to the barrel was the mechanism of the 

 breech, for which the material preferred was crucible cast-steel 



NO. 1207, VOL. 47] 



of a mild character, but capable of being hardened in those parts 

 exposed to the pressure of the bolt. The body was forged in 

 two operations under the steam-hammer ; it was then drilled and 

 subjected to along series of operations, in the course of which 

 the end was recessed to receive the screwed end of the barrel, 

 and the corresponding thread in the recess was milled out in a 

 specially-contrived machine, which insured that the thread should 

 always start in the same place relative to the gauged part of the 

 body, a point of great importance. The bolt, also of crucible 

 cast-steel, was forged under the steam-hammer. A special ma- 

 chine, invented at Enfield, was used to finish the bolt after 

 shaping. After machining, the bolts, packed in wood char- 

 coal in iron cases, were heated and hardened by immersion in 

 oil. The temper of the handle was then reduced in a lead bath. 

 The rest of the bolt was tempered straw-colour. The bolt-head 

 was similarly hardened and tempered. 



The other components of a complete rifle were mostly shaped 

 by mills built up to the proposed profile, or by copy-milling 

 machines. The process of drifting was used with good results 

 at Enfield. All such slots or perforations as had parallel sides, 

 and were not cylindrical, were so finished. The common prac- 

 tice in drifting was to push the drift, but at Enfield much better 

 work was accomplished by pulling. It was found that used in 

 this way drifts were very valuable for interchangeable work. The 

 sides were cut with successive teeth, each slightly larger than 

 the preceding one, andjthe whole length of the drift was drawn 

 through. Emery wheels were also largely used at Enfield as a 

 substitute for finish-milling and filing. The wheels ran under 

 hoods connected with a pneumatic exhaust that carried away 

 the heated particles of steel and grit. It was popularly sup- 

 posed that a machine once adjusted to turn out a component of 

 a certain size and shape was capable of reproducing such in 

 large numbers, all absolutely identical. This was so far from 

 being the case that no die, no drill, and no milling-cutter 

 actually made two consecutive articles the same size. The wear 

 of the cutters or dies proceeded slowly but surely, and it was 

 only possible to produce in large numbers components of dimen- 

 sions varying betweenja superior and an inferior limit. In small- 

 arm manufacture a variation of about one two thousandth of an 

 inch was about the amount tolerated, but it varied according to 

 the size of the piece. A difference of diameter of one two- 

 thousandth of an inch in the sight axis-hole, and in the size of 

 the pin or axis, would cause a serious misfit, whereas a similar 

 difference in the measurement of the magazine, or of the recess 

 in which it lay, would be quite immaterial. The operations of 

 gauging, proving the barrel, and sighting, were successively de- 

 scribed, as al>o the manufacture of the stock, which was of the 

 wood known as Italian walnut, though largely grown in other 

 countries. Among the smaller components, the screws were 

 mentioned as being rapidly produced by the automatic screw- 

 making machines of Pratt and Whitney. 



The Component Store received the various finished parts, 

 which numbered 159 1, or, including accessories, 1863, and 

 issued them to the foreman of the assembling-shop. Theoreti- 

 cally, the assemblers should have nothing to do but to fit and 

 screw them together, but in practice small adjustments were 

 found necessary. The amount of correction wa^ generally ex- 

 ceedingly small, and was done wherever possible with the aid of 

 emery wheels. The completed arms were submitted to inspec- 

 tion, and then issued in cases of twenty each to the Weedon 

 Government Store or elsewhere. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — The General Board of Studies propose that, in 

 view of the increased attention given to palaeontology in the 

 Geological Department, a Demonstrator in Palseozoology be 

 appointed, whose stipend shall be paid out of the students' fees. 



The Botanic Garden Syndicate report the completion of the 

 fine range of plant-houses, which have for some years been in 

 course of erection at a cost of some ;^6ooo. It is noteworthy 

 that the expense has been kept within the estimate. 



The Senate has determined to raise the fee for the Doctor's 

 degree (including M.D. and Sc. D. ) from ;^20 to ;,{^25, It has 

 rejected the proposal to increase the annual dues of under- 

 graduates from 175. to £%, and of graduates from 17.1. to £Xy 

 which was put forth in view of the financial needs of the Univer- 

 sity, by the Fees Syndicate. The proposal to accept life- 



