Hi ariel,
Quote:
|
Originally Posted by ariel
Virtually all handmade long blades have axial twist: when you hold the blade edge up and look along it's length, it is twisted more or less at least once or, more often, twice. Why is it?
Is it a reliable sign of a handmade blade?
The Japanese blades are as a rule very straight. What was done to control it?
|
I don't know what types of blades you are referring to, but discounting intentional deformation, we have to keep in mind that the thermal stresses imparted by the heat treatment of the blade very often induces some warpage. Thin slender blades being the most readily affected. In fact a considerable amount, if not all, of a Japanese sword blade's curvature is imparted by the quench.
Blades with a softish temper are the easiest to straighten out, a very tricky task at the best of times. Those that are harder are much more difficult to set true.
In my opinion a cutting sword blade that has an axial twist is badly flawed because the load imposed by the cutting will further twits it upon impact. On the other hand, on a short knife or thrusting blade, apart from aesthetic considerations, it is of little consequence. If memory serves me right, I think it was Richard Burton who remarked that it was hard to find a true (un-warped) triangular small sword blade, which as we know are used purely for thrusting.
In short, a flaw free and true blade of the correct temper was very difficult to obtain in olden times and this is why such swords acquired legendary reputations - They were the exception rather than the rule. Quenching cracks and forging flaws were often deemed quite acceptable, if the sword passed the proof test, whatever that may have been. I have a smallsword with some fine hairline quenching cracks in its forte, made by no less than Weyersberg (WKC) and also a Brit officers sabre with some quite substantial forging seams in its foible, yet sporting the proof mark. Both swords function as intended despite their imperfections (I tested them).
With modern steels, it is no longer necessary to impose a severe water quench to harden the blade and as a consequence warpage is minimal if at all present. But in the old days, they did not have the high alloy steels that make this possible.
Cheers
Chris