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clear hamon / hardening on the edge and on both jihada and shinogi


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Dear Robert.


Forgive me, I am not clear on your question.  Do you mean a hamon that rises to and goes above the shinogi or do you mean a hamon that is accompanied by muneyaki?    Or are we talking hitatsura?


Stand by for some fairly detailed metallurgy!


Looking forward to the discussion.


All the best.

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I think i read at usagiyas website that choji heads can become tobiyaki after a polish because the big heads are deeper hardned then the lower part.

After the polish they get disconnected from the hamon and become tobiyaki. In my opinion that means that a hitatsura blade dont have to lose its "felx" because the hardening could be mainly on surface. Also many blades have a lower carbon content in the core what makes it less likely to harden.

I dont think you can say how durable a blade is just by looking at hamon.


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Thank you all for your answers to my question.


The question is whether it has any effect (negative) on the sword in a real fight.


I still wonder why the smith makes a hamon that is also found in shinogi. I have seen a hamon structure that is similar to choji-ashi along the entire shinogi/mune and it looks deliberately made. 

 It may also have happened by mistake after clay has been put on the blade and after yaki-ire.

Can you imagine that it happens by mistake and that it is a beauty defect and that it does not affect the hardness of the sword or that the hardening can mainly lie on the surface?

Or is it deliberate to get extra beauty in the sword when selling to merchants during the Edo period.


I understand that you are thinking of hitatsura leaves with spots of tobiyaki etc. but I wonder if it is negative for the actual effect of the blade in a real fight.

Correct me if I'm wrong.


// Robert

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I think it was also a fad. It was apparently first developed (officially) by the Soshu tradition and then copied by others. If it had been so bad, I don’t think it would have stuck, especially during the Sengoku Jidai. And unless the first one was indeed a mistake, the others weren’t. Hitatsura creates tobiyaki, but the type of blade you seem to describe isn’t unheard of either.


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you are mixing up hardness and stiffness with flexibility, but I think you mean brittleness, toughness and resilience. Carbon steel alloys do not harden deeper than 4 mm down into the metal in small workpieces. That means that a 8 mm thick blade would theoretically be hardened through IF IT WERE MADE FROM MONOSTEEL THROUGHOUT.  But this is mostly not the case. By the way, the effects of hardening are different with test pieces of considerably higher mass (e.g. 10 by 10 by 10 cm). Annealing (YAKIMODOSHI) takes away some of the hardness and makes blades more resilient instead.

In composite constructions (with a flexible low-carbon core/SHINTETSU) blades will just harden in the high carbon KAWAGANE, often a thin layer of steel. This is the reason why blades can lose their HAMON if polished too often.

As Christian writes correctly above, you cannot judge a blade's properties by looking only at the HAMON. 

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