I'sS Report on the Art of making Jine Cutlery. , 



much worfe in quality now than formerly, which complaint I have alfo heard from other 

 intelligent artills. I did not aflc him concerning the art of forging, but take it for granted, 

 that it confifts in little more than the acquired flcill of managing the bar and the hammer, 

 with the precautions not to hijure the texture by ftrong hammering at too low a heat, or to 

 degrade the quality of the ftcel, by too much heat or expofure to the current of air from . 

 the bellows. 



Cutlers do not ufe any coating to their work at the hardening heat, as the file cutters 

 do ; and indeed it feems evidently unneceflary when the article is intended to be tempered 

 and ground. Mr. S. agrees with me, that the beft rule is to harden as little as poflible 

 above the (late intended to be produced by tempering. Work which has been overheated, 

 has a crumbly edge, and will not afford the wire hereafter to be defcribed. The proper 

 'heat is a cherry red vlfible by day-light. He has not found that any advantage is obtained 

 from the ufe of fait in the water, or cooling that fluid, or from ufing mercury inftead of 

 water; but it may be remarked, that queftions refpefting the fluid are, properly fpeaking, 

 applicable only to files, gravers, and fuch tools as are intended to be left at the extreme of 

 hardnefs. Yet" though Mr. Stodart did not feem to attach much value to peculiarities in 

 the procefs of hardening, he mentioned it as the obfervation and practice of one of his 

 workmen, that the charcoal fire fhould be made up with (havings of leather : and upon 

 being alked, what good he fuppofed the leather could do, this workman replied, that he 

 could take upon him to fay, that he-never had had a razor crack in the hardening fince he 

 had ufed this method, though it was a very commoa accident before. 



It appears to me from the confideration of other fails, that this procefs is likely to 

 prove advantageous. When brittle fubftances crack in cooling, it always happens from the 

 outfide contra£ling and becoming too fmall to contain the interior parts. But it is known, 

 that hard fteel occupies more fpace than when foft, and it may eafily be inferred, that the 

 nearer the flcel approaches to the ftate of iron, the lefs will be this increafe of diraenfions. 

 If then we fuppofe a razor, or any other piece of fteel, to be heated in an open fire with 

 a current of air pafling through it, the external part will by the lofs of carbon becom.e lefs 

 fteely than before ; and when the whole piece comes to be hardened, the infide will be too 

 large for the external part, which will probably crack. But if the piece of fteel be wrapped 

 up in the cementing mixture, or if the fire itfelf contain animal coal, and is put together 

 fo as to operate in the manner of that mixture, the external part, inftead of being de- 

 graded by this heat, will be more carbonated than the internal part, in confequence of 

 which it will be fo far from fplitting or burfting during its cooling, that it will be acled 

 upon in a contrary direflion, tending to render it more denfe and folid. 



One of the greateft difficulties in hardening fteel works of any confiderable extent, more 

 efpecially fuch articles as are formed of thin plates, or have a variety of parts of different 

 fizes, confifts in the apparent impracticability of heating the thicker parts, before the 

 flighter are burned away ; befides which, even for a piece of uniform figure, it is no eafy 

 matter to make up a fire which fhall give a fpeedy heat, and be nearly of the fame intcnfity 



throughout. 



