KNIFE SECRETS.

Hokitika Guardian, 22 October 1921, Page 4

KNIFE SECRETS.

(By a Metallurgist). The finest, knives in the world are made in Sheffield. Have you evci noticed a dirty-lookiug patch on the blade of a table knife near tho handle end, as though someone had placed a thumb on it before tile steel was quite solid y . 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 lainous "shear steel that it is found. “Shear” steel originated in Shelheld 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, h.v processes so expensive that only the cutting part ol the knife is made from it. The tang which is secured to l he handle, and the shoulder at the end ol the blade, are of a cheaper steel welded on: hence the patch. This method gives the finest cutting I knife in the world at a competitive ; price. . . [ Other countries tried m vain to make a knife which would keep its cutting e,1,.e like a Sheffield "shear” steel knTfe. They used the same materials, hut failed to get the results desired, and so the superiority was ascribed to seine secret ill the hardening of the l)l:icle. , ..

iSnir.o queer mu.-, ll'.cm true, were given, such ns the use oi Derbyshire water, of mixtures of chemical’s in the water, ami hardening in pigs’ blood. But the secret remains a secret to-day. "Shear” steel, it may he mentioned, contains a small quantity of slag embedded in it. but whether this has anything to do with the line edge is not known. Another very excellent class oi knives are the rustless ones, and these also originated in Shefhekl. lo these, in addition to the iron, are varying amounts of one or more of the following:—Chromium, cobalt, molybdenum, Vanadium, nickel, and tungsten, which are responsible for the corrosion-re-sisting properties. There are some people who imagine that rustless knives may he poisonous. This, of course, is absurd, their retained brightness tending to safety. Another widespread belief is that rustless cutlery will mu retain a keen edge. This again, is incorrect. Some of the earlier sl>eeimeiis may have been a lit He lacking in this respect, hut those now being made have a splendid edge, which they retain. They keep their relish indefinitely ami call he used with fruit or vinegar without any permanent stain. Vinegar sometimes appears lo stain them, hut this is caused by leaving vinegar on them until it dries up. Mann water immediately removes this.