Sir John Robison on Cutting Curved-faced Files, 87 



pose that blanks should be prepared as if for thin equalling- 

 files (i.e. of uniform thickness and breadth throughout), and 

 that they should be struck on one or both faces, of the degree 

 of fineness required. This having been done, I propose that, 

 by means of a screw-press and swages of copper, or other soft 

 metal, they should have the required degree of curvature im- 

 pressed on them before being hardened, and that, in this man- 

 ner, files with curved faces, but with the teeth of equable 

 depth all across them, should be obtained. 



In a similar manner I propose to form three-quarters round, 

 or even cylindric, smooth files, by cutting flat blanks on one 

 face, and then bending them on steel mandrils into a tubular 

 form previous to hardening them. 



On communicating this plan to the eminent manufacturer 

 Mr Stubbs of Warrington, I learned from him that something 

 of this kind had been attempted by his house, but abandoned 

 on account of the difficulty experienced in getting the files into 

 the curved shape after they were struck. Mr Stubbs at the 

 same time sent me a file so made, thirty years before. This 

 file at once explained how the difficulty had arisen, as, instead 

 of the blank having been made of uniform thickness and 

 breadth, it has been fashioned like an ordinary crossing file, 

 and therefore not susceptible of being squeezed into the re- 

 gular curved shape by simple pressure. If Mr Stubbs had 

 thought of making the flat blank, he would no doubt have suc- 

 ceeded better ; and the formation of tubular files, which he ac- 

 knowledges never occurretl to him, must have followed the 

 other at a short interval. 



Edinburgh, November 14, 1842. 



REPORT or COMMITTEE. 



Agreeably to the remit made to U8 by the Royal Scottish Society of 

 Arts, of date the 13th December last, on a paper read by Sir John Robi- 

 son, K.H., on cutting and manufacturing half-round and round files, — 

 your Committee beg to report, that tliey have also had remitted to 

 them three half-round pillar files, manufactured by Messrs Johnson, 

 Cammell, & Co., Sheffield, which were exhibited at the Society's meet- 

 ing, on the 23d instant, made in the manner suggested by Sir John. Two 

 of these files were cut on the convex side only, and the other on the 

 concave side also, and appear to your Committee to be very fair speci- 

 mens as a first trial, although they are not so straight, and of so uniform 

 curvature, as might be required. 



