KNIFE SECRETS.

Hauraki Plains Gazette, Volume XXXII, Issue 4326, 5 October 1921, Page 2

KNIFE SECRETS.

(By a Metallurgist.)

The finest knives in the world are made in Sheffield. Have you~ ever noticed a dirty-looking patch on the blade of a table knife near the handle end, as though someone had placed a thumb on it before the steel was quite solid ? The presence of this mark is a good test that the knife is of the best possible quality, because it is only on knives made of the fam.ous “shear” steel that it is found.

“Shear” steel originated in Sheffield centuries ago; and was so called because of the great demand for it for tailors’ shears or scissors. It is made from Swedish bar-iron, which is the purest in the world, by processes so expensive that only the cutting part of the. knife is made from it. _ The tang which is secured to the handle., and the shpu,lder at the* end of the blade, are of a cheaper steel welded on: hence the patch. This method gives, the finest cutting knife in the world at a competitive price.

Other countries tried in vain ‘o make; a knifte which would keep its cutting edge like a Sheffield “sheaf” steel knife. They used the same materials, but failed .to get the results desired, and so the superiority was ascribed to some secret in the hardening pf the blade. Some queer explanations, some of them 'true, were given, such as the use of Derbyshire water, or mixtures of chemicals in the water, and hardening in pigs’ blood. But the secret remains a secret to-day. “Shear” steel,, it may be mentioned, contains a small quantity of slag embedded in it, but whether this has anything to do with the fine edge is not known.

Another very excellent class of knives are the rustless ones, and these also originat(ed in Sheffield. In these in addition to the iron, are varying amounts of one or more of the following: Chromium, cobalt, molybdenum, vanadium, nickel, and tungsten, which, ai’e responsible for the corrosion-resisting properties. There are some people who imagine that rustless knives may be poisonous. This, of course, is absurd, their retained brightness tending to safety. Another widespread belief is that rustless cutlery will not retain a kden edge. This is incorrect. Some of the earlier specimens may have been a little lacking in this respect, but those now being made have a splendid edge, which they retain.