Thread: Natural Stone Grit Confusion

This question is mostly for the people who actualy are able to estimate the grit of their naturals and in particular apanese stones. From my very limited experience in with my Nakayama, I would have a difficult time giving an estimate of it's grit and I know some people are able to estimate. When you estimate, are you giving an average of how it is cutting freshly lapped?
I start out with a slurry cut in with a DMT. At that point, the grit has to be pretty low, as it is cutting very fast, but not so low as to leave deep scratches. Maybe a fast cutting 5000? Then moving to water I hone and eventually gradually lightening pressure and finish up to where I can shave. Since it produces a uniform haze finish, I would not even begin to know how to estimate the final grit especially being "raised" on synthetic hones where you can literally see bigger scratches for 1200 than 8000 etc.

Could it be as Alan Watts said of Zen ? Those who know don't say and those who say don't know. I haven't got a clue.

In doing a comparison, there are a few things to consider, but the level of polish and/or scratch pattern are, imo, not the best to go by. I mostly go by the way the edge feels off a hone, and say something like "hone x gives an edge like hone y."

the place I got my Japanese finisher, has grit test pics.
Alex has probably dealt with Japanese stones since forever so I trust his grit estimates.
You can ask him if he is willing to test your stone and give you a grit estimate.

I was just going to mention Alex Gilmore's photo tests. One thing about those tests, though. They certainly contain more objective information than any other method in that they are based on photographs. But it seems to me like the estimate of a grit based upon the appearance of striations in metal in a photograph is pretty imprecise too. I'm not doubting Alex's estimates, as he seems to know what he is doing, but I wonder whether anyone else would be able to take the same photographs and reach the same conclusions without the kind of background and "feel" for this that Alex does.

Originally Posted by JeffE

I was just going to mention Alex Gilmore's photo tests. One thing about those tests, though. They certainly contain more objective information than any other method in that they are based on photographs. But it seems to me like the estimate of a grit based upon the appearance of striations in metal in a photograph is pretty imprecise too. I'm not doubting Alex's estimates, as he seems to know what he is doing, but I wonder whether anyone else would be able to take the same photographs and reach the same conclusions without the kind of background and "feel" for this that Alex does.

Only photo evidence is not good enough, Alex has a lot of experience and that is what gives credibility imo. a better test would be to work the slurry on a natural stone then take an SEM image and see whats the size of the grain.

well SEM pictures are probably not the most cost effective way to investigate an edge as a set of SEM photos can cost up to 10.000 Bucks, I guess.

I would go with the "feel". I have my ways to test an edge, not a stone.
The TPT in the high grit range is quite effective as well as the HHT and of course the shave.

A fast cutter isn´t of course always a lower grit hone.
The higher the content of abrasives, the faster it cuts.
I came to the conclusion that most j-nats are very, very fast cutters for their grit range and have high amounts of abrasives.
A slurry on a j-nat always makes it cut really, really fast.
Of course the results change, these stones tend to produce a hazy finish (kasumi) when slurried,
even though they polish when used without slurry.
And most of the time the stone used in polishing mode without slurry
will not be strong enough to polish out the hazy finish left by his own slurry.
Interesting, me thinks

Originally Posted by Lesslemming

well SEM pictures are probably not the most cost effective way to investigate an edge as a set of SEM photos can cost up to 10.000 Bucks, I guess.

1 hour on the SEM @ my University is 160 bucks.

Originally Posted by mainaman

1 hour on the SEM @ my University is 160 bucks.

Out of curiosity, how much work can a relatively experienced user do in that time? Say you had a pile of razors and wanted to take one good-looking picture of the edge of each - how many could you do?

When I bought my Nakayama from So at Japan Tool I tried to get him to estimate the grit of my stone, all he would say was that it would be fine enough, and since he didn't do any closer estimate, I'll just go by how the edge feels of the hone.

The grits test at japanblade has been discussed here, it's an interesting read, with some interesting questions about his test procedure.