Tempering in the Bohi.

[Babu]

I wanted to ask the more experienced members about the place in construction for Bohi to occur.

In many swords I would imagine it comes after tempering so that the full strength and weight of the sword is offered up to the heat.

So my question is. How can a deep Bohi exhibit obvious temper in the form of clear misty martensite thicker in places but all the way along the blades hi? Is it that the martensite developes deep into the metal so carving doesn't remove the temper ?

Any thoughts?

Apologies if this question has been raised before.

Blade exhibits Hitatsura Hamon on masame.

Regards Adam

[Jamie]

Can you post pictures?

You might post a full length pic and a few of the tobiyaki at least.

[Babu]

Of course but please forgive the poor photography skills.I only have a phone camera.

Regards Adam

[Jamie]

Is it shinogi zukuri, or shobu?

It does appear tempered in that second picture

[Shugyosha]

Hi Adam,

 

It makes sense if it's a hitatsura temper to which a bo hi was added later - either by the smith or at the request of a later owner. Same would go for a blade with mune yaki potentially.

[Babu]

Sorry more questions come to mind. Would that not be difficult and risky work on a heat hardened/toughened surface?

If we osuriage a blade it must be heated in order to work the (old blade material) new Nakago. More so where the blade has been tempered? Also would the tempering process go right through to the other side on such a thick area of steel. I can see nie and nioi clear as day on the surface of the Bohi.image one and four show this.

Regards Adam

[Ken-Hawaii]

Yes, Adam, you're right that it is more difficult to carve a bohi into hardend steel, but not impossible, especially if that would remove a defect that makes the blade unsalable.

[Shugyosha]

Hi Adam,

 

What Ken said - it would be tough going but can be done. You do occasionally see horimono carved a little into the hamon if the hamon reaches high up the ji and there isn't space. 

 

I can't remember where I read it but apparently you can have a hot or cold suriage for a blade. Logically the better option would be to re-heat to take away the hardened edge after the new ha machi, but it can be left in place. 

 

Yep the nioi and nie are there in your sword. As you said earlier, the order of things should be cutting the hi after yaki ire - there's no point in going to the trouble of cutting the hi before hardening the edge as this creates a lot of stress and if the edge cracks you've lost the work that has just been put in so, unless it has been re-tempered (the only possible other option), the hi has been cut after your blade has been given its hamon. There could be several reasons for this - as Ken said to conceal a defect or to lighten the blade for an owner who has suffered an injury or has gotten old or who practises a style of fencing that is done better with a lighter blade, or even just likes the sound a blade with hi makes when you swing it. 

 

I've not thought much about this before, but I can't honestly remember seeing a hitatsura blade with a hi - that might be my Alzheimer's though and no doubt someone will point to a load of them now I've said it. Perhaps this is because of the difficulty of cutting it or perhaps because it works against what the function of the hitatsura hamon (if it has one) which one would think is to stiffen the blade. 

 

I hope that's helped answer some of your questions though, with Nihonto, definitive answers can be hard to pin down.

[raaay]

 ? Would this happen if a sword was re-tempered ?

[Babu]

Gentlemen thank you you have been invaluable. Its on an old tachi cut down to handachi/O wakizashi.it's osuriage and has four mekugi ana in the new Nakago so it's been adapted to all the differing styles through the years one would guess.

Regards Adam