Bo-Hi

[Guest Rayhan]

Hi all

 

I know Bo-hi function has been discussed but I would like to know if certain schools used specific styles of Bo-Hi as their own element, as in proprietary to them (until copied or borrowed of course)? Any opinions would be very helpful. Thank you. 

 

Rayhan

[paulb]

Hi Ray

I think many references point out that specific styles of hi, particularly where and how they terminate are indicative of particular schools. But as you point out some styles were copied from school to school so I think any identification of a particular hi with a given school is a generalisation.

[Ken-Hawaii]

I tried to track hi styles down, too, Ray, but other than a couple of generalities, I found the same thing that Paul did. Bo-hi seem to have been included for lessening the overall blade weight, & for strengthening the structure.

[Jean]

It is a trademark of Miike school.

[Guest Rayhan]

So Miike were the first? Thank you guys for weighing in, the search continues.

[Jean]

I don’t know if there were the first to have a bohi on a blade, but AFAIK, they were the first to generalize it in their school. All Miike school daito I have seen had bohi, included utsushi of the school.

 

Now you can refer to the « Connoisseur’s book of Japanese swords » and look at bohi as kantei point.

[Guido]

Bo-hi seem to have been included for lessening the overall blade weight, & for strengthening the structure.

 

Taking away material will always weaken a structure, not strengthen it. However, by carving a bōhi, the weight of the sword can be reduced without compromising its strength too greatly. The same approach is used in engineering in the shape of the I-beam.

[Guest Rayhan]

I don’t know if there were the first to have a bohi on a blade, but AFAIK, they were the first to generalize it in their school. All Miike school daito I have seen had bohi, included utsushi of the school.

 

Now you can refer to the « Connoisseur’s book of Japanese swords » and look at bohi as kantei point.

 

Noted Jean i shall hit the books 

 

Guido, strength is a generalised term but the addition of a groove definitely helps with the rigidity of the swords vulnerable area (area used in defending and mostly prone to stress) so it can bend without warping and is lighter in hand.

[ROKUJURO]

Rayhan,
 

from a technical point of view, a groove is not an 'addition', but you take material away, as Guide pointed out correctly. The special effect of a groove (depending on its size) is that you end up with less weight of the blade which makes it faster in combat. The other side is that you have considerably more rigidity when compared to a thinner blade (= less KASANE) of the same weight (I-beam principle as mentioned by Guido). 

All these factors have been developed through centuries by trial and error, so there are certainly no calculations and figures involved. But the basic principles still apply.