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grits of japanese sword stones ??

john marcus

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Here is a rough estimate as I understand:


Arato @ 180 - 220 Grit

Bensuido @ 280 - 320 Grit

Kaisei @ 400 - 600 Grit

Chu-Nugura @ 800 - 1000 Grit

Koma-Nugura @ 1200- 1500 Grit

Uchigumori (hato is softer, jito is harder) @ 3000 Grit

Hazuya @ 8000 Grit

Jizuya @ 15000 Grit


As I understand it, Kasumi-do is a type of uchigumori that has quite a range of hardness and grits. I do beleive it to be @ 3000 grit, and quite variable in hardnesses. It has a more recent history in traditional polishing, taking the place of uchigumori as it is depleted.


I am sure you know that the natural stones vary in grit from spot to spot on the stone and from stone to stone. Also, this does not take into account hardness of the stone, which is very important when doing the shiaji-togi as to bringing up certain appearances or suppressing others.


Hope that helps,



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  • 14 years later...

Sorry to ressurect this thread, but I was doing a related search, and this came up! I'm pretty sure the numbers above are incorrect. Here's closer to what I would put them:


Kongo do (replacement for Arato do) ~400

Binsui do: 800-1000

Kaisei do: ~2000

Chu Nagura do: 4000-5000

Koma Nagura Do: 7000-8000

Uchigumori: 10000-12000

The Hazuya are just softer flakes of Uchigumori, and the Jizuya are a bit finer than the uchigumori, maybe something like 13000.


This is all based on comparing the stones from Namikawa Heibei to their equivalents from Shapton, and natural equivalents. Using a comparable progression on the Shapton, I can reliably get sashikomi. Using a progression of stones suggested by Shannon, sashikomi by the uchigumori would be impossible.

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  • 4 months later...
Posted (edited)

Part of the discrepancy might have to do with the standard being used. For instance, Uchigumori may be 10000-12000 JIS / 3000 FEPA-F.


JIS (Japan) FEPA-F (EU stone) FEPA-P (EU coated) CAMI (US coated) micron
20000 7500     0.5
16000 4000     0.7
8000 2000 9500   1.2
6000 1500 7000   2
4000 1200 5000   3
2000 800 2200 1500 6
1200 600 1500 1000 10
1000 550 1200 800 12
800 500 1000 500 20
400 320 400 360 30
320 280 280 320 40
240 220 240 230 60
120 120 120 120 110


n.b: there are many tables on the internet with slightly different numbers -- this is the one I use, no garantees, ymmv.


Edited by Francis Gastellu
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That's a fair point! There are a lot of US/Canadian artisans (like Dave Friesen, Doug Blaine, and Jim Kelso) that focus on a primarily low grit progression for polishing, whereas traditionally in Japan they focus more on fine grits. They can both produce a very fine polish, but the method employing low grits tends to give the surface a "faceted" look. I've noticed this in person looking at Doug Blaine polished swords, and looking at Dave and Jim's work online. Both the US and Japan have meaurements that are roughly "grits per inch," and that's what I'm talking about, whereas the european standards are rarely encountered here. 


There's not a perfect range, but I find that 4000 is the finest grit that isn't polishing (there's a distinct visual difference when you go finer than that). There's a lot of overlap between chu nagura and koma nagura grit stones, so those are more of a spectrum. Also the range between kongo/binsui/kaisei is more fluid, though you need at least three to span the gap. Uchigumori and suita in general are fine enough that on most steel you can't see scratches, but if you polish copper with the same stone you'll still see them.

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