Thread: What actually is Hardness in natural stones, and how it affects sharpening

trust me, it is not that simple

Sharpening is the act of removing steel, it is a grinding process that is used to create a geometrical profile to a blade

That is right, but what about polishing? There is evidence that at high grit ratings, the grinding action (ie. removing steel) gets less important.
Tha major action here is a plastic deformation, rather than grinding (even though always both is present). Grinding per definition involves removing metal at a fast pace,
wich is hardly what we want to do. I would suggest reading some of this, b/c we always think there is so little knowledge about sharpening
but indeed there is. But it is disguised

Grind - Wikipedia, the free encyclopedia
Polishing - Wikipedia, the free encyclopedia

and heres something reall special, quite in depth theory of the difference in polishing and grinding
Metallography, principles and practice - Google Books

And heres another one about polishing mechanisms
http://www.asminternational.org/cont...85G_Sample.pdf

The hardness of a stone and a stones cutting abilities are related

Maybe, but there are many exceptions to that rule. Not only is "hardness of a stone" still undefined,
but what I would call a very hard synthetic stone (the shaptons, 16000 or 30000 for example, or the pro 12000) may be extremely quick
at removing scratch patterns and cutting microbevels etc. The Shapton 16.000 is staggeringly quick and can (not should) be used after the Cerax 6.000 with a couple of circles.

My Shoubudani is it appears to me a harder stone than my Nakayama Kiita.
But it also appears to me that it is quicker.

So my prediction is that there won´t be any consens about what is hardness and how does it affect a stones performance.
There is too much to take into consideration