Thread: Japanese stone grit levels: Suita, Narutaki, Nakayama

I found some pics at www.thejapanblade.com of some REALLY REALLY REALLY REALLY (really) nice japanese stones, along with some pics of the grit scratches for each type of stone compared to the others as well as man-made hones.

If you'll look at the scratch pattern differences between the 15k hone, 30k hone and Nakayama stone, the largest improvement is obviously (to me anyway) between 30k and the Nakayama, which suggests a grit rating of 45k or more. The website's author rates most of them between 40k and 44k, but to my eye, it looks much finer.

The second to last pic (nakayama #8) is rated, by the author, as the finest stone in his collection

The last pic is of an Asagi(nakayama #20), while the other Nakayama tests were Kiita stones.

It's interesting that one of his Suita stones looke every bit as fine as the Nakayamas, I thought they were generally lower in grit.

Check 'em out, discuss your take on 'em, etc.

Very interesting, Russel. Thanks for posting these pictures. I want to study them for much longer than the minute or two I had right now.

Did the author talk about the actual honing process in relation to slurry either released from the stones or by way of a slurry stone?

When I see pics of the Nakayama #1, Narutaki test and even the Nakayama #8, the "sandblasted" rather than striated scratch patterns I believe show a fair amount of slurry being used during the honing process. Honing with water only produces scratches whereas in my experience (with non-J Nat stones) honing with slurry is where you get the satin bevels.

Chris L

I would venture to say that there is some sort of slurry inherent in the method of honing japanese plane irons (which is what those are pictures of), and he mentions that the stones are easier to use with a slurry, but doesn't say whether he intentionally generated one for the tests.

If you go to the website for #8: http://thejapanblade.com/test_.htm, there are larger photos where you can see more detail.

Same for #1: http://thejapanblade.com/test.htm

I agree, it looks like there is slurry abrasion, but in the larger shots you can still see very fine linear scratch patterns as well.

BTW, in case someone doesn't want to check the prices on the website, let me just say that the author is charging anywhere from about $1500 to $4000!

It's also very cool how the author used flaws in the steel further up from the bevel as a point of reference for each picture.

Chris L

One of the best comparisons of the different kinds of stone against one another: NATURAL GRIT TEST

That is one of the few photo sets where you can actually see the edge of the blade in question, notice that it doesn't get significantly sharper after 1k grit, just a whole lot smoother. Interesting, eh?

Chris, I agree, using those inclusions in the iron backing material as reference is pretty neat.

I find it very difficult to tell edge width with the shadow line underneath.

Mr. Gilmore's collection of rock and iron is quite off the chart ain't it?

"Rock Hound", isn't that a much more affirmative, and positive use of language rather than referring to a perfectly normal and acceptable activity as a disorder?

Suita can be very hard, and the hardness of the stone has a direct correlation with its fineness. The problem with some Suita stones is that they can contain scratchy holes that make them unsuitable for honing. And as I discovered, these holes can lie just fractions of a mm under the honing surface and become an issue after a lapping or two. They can be lapped away until a smooth layer is again found (well, I keep telling myself that anyway), but because it is such a hard stone, that takes a while....

But they are interesting photos - I've been ogling that site for a while now and although the stones seem fantastic, they are a little too rich for my blood. I find the Narutaki scratch pattern interestingly smoother than I might have guessed at.

Have you guys also noticed that even though a natural stone may be rated at say 16K, it feels completely different to an artificial stone's edge of the same grit? I think I read somewhere that the naturals have slightly non-uniform particles so that the striations are more diverse than an artificial - the whole edge will go on an artificial, whereas only bits of the edge might go on a natural. Makes the natural edges seem more robust to me, and I've heard they do last longer... Time will tell I guess.

James.

Jimbo,

I've heard many woodworkers say that the natural stones give a longer edge life than man-mades, but I don't necessarily believe it. I'd very much like that to be the case, and my experience is that they do polish differently as compared to man-mades, but I wouldn't put my name on it just yet. There are just so many variables inherent with measuring edge life that it may never be confirmed, or denied, in a conclusive manner. I do like your theory though.

Kevin,

I was seeing that little black line as the edge of the blade, not a shadow, but you may be correct, hard to tell.

Yeah, "rockhound" is more dignified, but if you call it a disorder, you have side stepped the requirement of acting rationally. "I can't help it, I have a disorder".

I believe there may be an indirect correlation to the fineness of a stones abrasive and hardness. Hardness does have a direct correlation to depth, fineness likely has a direct correlation to a given stones location in the strata.

I really do not want to misrepresent myself. I am no expert, just excitable.

thanks for the cool pics!
very interesting...