February 23, 20188 yr https://m.youtube.com/watch?v=TgtFgJR-U_E I’m not an experienced knife maker so several questions came to mind after watching the linked video? Is this Japanese bladesmith annealing his fully forged knife blades in charcoal to add carbon content? And then when he is working the blade, apparently cold, right after that on a wooden stump, is that to work harden the steel? His use of a drawknife to shave the bevel also is something that I’ve never seen before. Amazing concept.
February 23, 20188 yr 1 hour ago, MilwaukeeJon said: is that to work harden the steel? Maybe and maybe also to remove scale?
February 23, 20188 yr The annealing was done in ash, not charcoal. The ash simply insulated the hot steel, allowing it to cool very slowly. The annealing enabled the cold working. Hardened,or even half hard, steel would break or crack when worked cold like that. The video does not show a tempering process... but surely there was one. The "drawknife” is actually a sen... a traditional Japanese bladesmith’s tool. The sen is made of very hard steel and is more commonly used for things like cutting blood grooves and fullers on swords. Personally I would use my belt grinder for creating this sort of bevel... it’s faster. IMO this much cold work is inviting trouble... but this smith obviously knows what he is doing.
February 23, 20188 yr Author Thanks for the info, bigfootnampa. I understand that one can work the annealed blade but am more curious as to the logic behind this smith’s fairly aggressive working of the flexible thin blade on the wood stump (at least I think it is a stump given how much the blade curves up with each hammer blow). Is he simply planishing or is there some other reason for this process? Seems to be rather aggressive cold working. Thanks in advance. To my eye, it looks like the annealing is done in charcoal slivers that then get lit from the heated blade and burn overnight, turning into ash (from 5:37-5:55 in the video). Would there be some carbon adding effect from this or is it just another way to assure slow cooling? (Sorry for the dopey question but I’m not very well informed on the scientific side of all this). The sen is pretty amazing.....may be troublesome and inefficient but I want one!
February 23, 20188 yr Charcoal isnt going to add any carbon that way, and as for the comment about Blood groove ? Arrrrrrg !!!!!!!!!!!
February 23, 20188 yr 12 minutes ago, Steve Sells said: and as for the comment about Blood groove ? Arrrrrrg !!!!!!!!!!! Breathe, Steve, breathe! Actually, now that you're here, there's something I wanted to ask you, in reference to the observation above about hammering on a cold blade. I'm under the impression that this is not uncommon in Japanese blade making, where the softer backing steel of a laminated blade allows for some degree of straightening after the heat treatment process. Is this correct, or am I misinformed (again)?
February 23, 20188 yr I have no training in Japanese blade work., I dont know, the very idea of hitting a hardened blade scares me though, Ask JPH, as he and Mr Egnath did a lot of work on Japanese stuff back in the day
February 23, 20188 yr For example, 8:12-8:21 of this video come after the hardening (7:18-7:35): https://www.youtube.com/watch?v=UqwxkyaSws8 Note the rather significant curve to the blade at this point in the process. @JPH, what say you?
February 23, 20188 yr 1 hour ago, Steve Sells said: Blood groove ? Arrrrrrg !!!!!!!!!!! Don't worry @Steve Sells you weren't the only one who winced (to put it mildly) at the "blood groove" comment.
February 23, 20188 yr Oh come on, everyone knows that the fuller in a blade is to let air into the body and make an air embolism that kills the victim instantly. Seriously now. Why is the Japanese smith wetting the hammer and flooding the anvil all over?
February 23, 20188 yr Of course... I've heard wetting the anvil and hammer helps blast scale off the workpiece, though I may be totally wrong?!?
February 23, 20188 yr I thought that it was the ringing in the anvil that wipes the scale off the anvil Oh I see. scale off the workpiece ... mm ... yes that makes sense.
February 27, 20188 yr To me the cold working is a poor idea. Obviously this Smith makes it work with his steel. I would not suggest such techniques. Sorry about the blood groove mention... I had no idea that it was such a sensitive topic! I’ve never made one and never intend to, but I might make a fuller someday. Does that get me off the hook? I suppose that the water dipping was intended to loosen scale... it seems like a very sketchy strategy to me! I’ve seen it in numerous videos but it never looks very effective to me. If you want a sen you’ll probably have to make it. I’ve seen some good tutorials. I think they are not too difficult. I’ve ground one from solid carbide steel. It works okay but I’m not really sold on it. My belt grinder is amazing!
February 27, 20188 yr 2 hours ago, bigfootnampa said: Sorry about the blood groove mention... I had no idea that it was such a sensitive topic! I’ve never made one and never intend to, but I might make a fuller someday. Groovy.
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