Thread: Can you get GREAT result with nagura and AVERAGE Jnat stone?

Originally Posted by Nikolay

I have read the post once more and
I almost accept that point
but I don't like the word hardness.

The hardness itself is not what we need.

The subject is more complex, than just hardness of stone
and include such characteristics as uniformity and density of particles (grains). The more uniform is grain in size and form
the more dense is grain the better is stone for finishing honing.

IMHO this is very accurate observation, now imagine a Jnat that has all the characteristics you mentioned above but is also very hard in addition to that, that produces killer edges.

The second thing we need is the condition stone of working surface.
It should be lapped very plain and very smooth.

I find this definitely makes a difference.

Originally Posted by JimR

I would say they are equally important, with one condition: the stone must be fairly hard.

Basically, and I might be opening a can of worms here, I think hardness of the stone is more important than "grit" when we're talking Japanese hones. I honestly believe that there's a real, measurable reason for this, namely: the "grit" in the Honkuchi naori Japanese hones is all pretty much the same, it just depends on how much is exposed, and at what speed, in the honing process. So hard hones = better control of exposure.

I have read the post once more and
I almost accept that point
but I don't like the word hardness.

The hardness itself is not what we need.

The subject is more complex, than just hardness of stone
and include such characteristics as uniformity and density of particles (grains). The more uniform is grain in size and form
the more dense is grain the better is stone for finishing honing.

The second thing we need is the state of working surface.
It should be very plain and very smooth.

Good examples are arkansas and belgian yellow coticle.
The size of their grain is bigger than grain of toishi, but their grain is well shaped and very uniform.

IMHO translucent arkansas with surface lapped to mirror glace is the best stone ever for the final touch to the edge.

BTW the japanese guys appraise such a translucent arkansas very high for it's hardness and uniformity
Here it is SEM micrographs of arkansas to illustrate the idea of grain shape and uniformity:



some other micrographs of Arkansas stones can be found here:
http://www.google.ru/images?q=SEM+mi...w=1280&bih=821

the good micrographs of toishi:
http://www.toishi.jp/bunseki1.html

SEM micrographs of toishi are presented there as PDF documents:
http://www.toishi.jp/bunsekisitu/kiirosuita_seibun.pdf
http://www.toishi.jp/bunsekisitu/aisa_seibun.pdf
etc.

note the difference in shape, size and layout of grains.