[TheForge] Samurai program

[A Vida]

schade at acegroup.cc wrote:
> 

 > In one segment they
> say that the curve in the finished blade is made by quenching
> (clipped/pasted below). I am not a knifemaker or student of
> damascus/samurai swords/patternwelding/etc but I have never
> heard this before.
> 
> Is it true?
> 

	It can be.  The better answer is that it depends on how much sorii 
(curvature) is desired and its specific form.  Sorii varies according to 
the smith and the tastes of the person for whom the sword was made. 
Sorii can be slight or severe - it can be uniform along the length or it 
can vary, usually with a shorter radius toward the hilt and broadening 
moving toward the point.

	It is also partly determined by the depth of the temper line.  For a 
given depth of sorii, a shallow temper line will require more forged-in 
curve than one with a deep one.  It can be the case that where there is 
to be a deep line and a very shallow sorii, the smith may have to forge 
in a small bit of counter curvature.  On quenching, the blade will be 
pulled up into a positive curve.

	Another way to regulate sorii is to harden the spine as well, which 
will counterbalance the forces at the edge.