Thanks and some advice about naguras and suita stones?

First everyone, thanks for this site. I'm a woodworking but have reading deeply here about sharpening. I would put my edges against almost any woodworker I know prior to coming here. But I've learned some things here that have allowed me to more quickly and easily work some very gnarly, beautiful, expensive boards. So, thanks for that!

I'd like to get some advice about nagura use with Suita stones. One of the stones I have is an 'ohira suita' I bought off ebay (cheap!!!). It was low cost from a one time seller, and so I have no idea what it really is and don't really care. What's important is: it's VERY hard, right up there with a shapton stone, it does have 'su', and it leaves a wickedly sharp (what I call a 'curly bubinga grade' edge) *IF* I'm willing to spend the entire length of "revenge of the sith" rubbing a plane blade on it. I need a way to raise a slurry. I did use a diamond stone to raise a slurry and that seemed pretty brutal. Scratched the hell out of the stone and it'll take while wear that out: I don't really want to do that again.

I've read on Alex Gilmers site that you shouldn't use nagura with Suita stones because the nagura grit will get into the holes and you'll never get the coarser particles out. His site also says that you can use tomonagura. So here is the thing. I do have a tomonagura that came with another stone I have, and that (very hard) stone is supposed to be very, very, very fine.

Would I be risking anything if I used this tomonagura on the suita stone to raise a slurry?

Depends on how hard the tomo is in comparison to your stone. I have 4 jnats and 2 tomos. My shuobodani is softer than one of the tomos that's why I got the second. Or you can get a dmt card in 600 grit or dmt 6x2 plate to raise a slurry.

You can use any of your other stones to try as a tomo is a piece of stone(if its matched correctly it will be close to the main stone).

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Originally Posted by bill3152

You can use any of your other stones to try as a tomo is a piece of stone(if its matched correctly it will be close to the main stone).

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But am I correct in my logic that the tomo has to be finer than the suita?

Well to make the slurry do what its supposed to IMO the base stone should be a little harder so when you are honing, the base stone will crush the slurry smaller and smaller. Finer would be good as the slurry will not have as much to go to break it down. Large particles would result in large scratches.

JG
Alex here. I did suggest that you do not use a nagura for raising a slurry on a suita stone, and this is a "rule of thumb" that was first proposed by So-san of Japan-Tools. Don't let this stop you from testing out nagura on your suita, you might find a good combination that does work. The caution was that some hard grit particles might get caught up in the su and would scartch your blade, and it could be hard to remove them. If you have a good quality piece of tomonagura that does not have any veins of darker material you might be just fine so don't let the idea of stop you from testing. It is the rogue hard particles that can scratch a blade even on tomae type stones, ones that break off from the main stone in larger pieces and resist breaking down like normal Jnat grit tends to do, or alternate mineral particles (usually dark) that can scratch.

About your diamond plate, it may be just too agressive, the DMT brand can be like that, I favor a worn out Atoma for raising a slurry or razor honing or tools. A worn Atoma 1200 can be your best friend for really hard stones but if you can find a quality tomonagura to provide a slurry that is the traditional way in Japan. Some fellows balk at the idea of using a diamond plate on their valuable Jnat, and I can appreciate this. I would suggest that raising a light slurry with a diamond nagura will wear your stone out only slightly faster than not using a DN. Using a tomonagura will also wear out your base stone and maybe slightly slower than a DN. With really hard stones some sort of media is needed between the steel and the stone, for medium hard stones you can with a good steel/stone match get away without some slurry as the stone will provide some loose grit during the sharpening/honing process.

I have lapped low areas out of hundreds of Jnat stones using the freshest Atoma plates I have on hand, hard stones always take longer than I think they will, softer stones are manageable and much easier and quicker. These medium hard will kick up a slurry under a blade on their own, hard stones require more prompting. If you spent an hour on a hard Jnat lapping it down, I bet you would have a hard time measuring weight or thickness wise how much stone you lost down the drain. I have literally spent hours lapping flat a level 5++ or 5+++ Jnat. Arkanas are harder even yet. Using a diamond plate on a hard stone for 5 to 10 seconds will not waste that much stone, and with that slurry, your stone will transfrom to a different sharpening/honing animal, from a house cat to a cheeta.

Good luck, and don't be caught up to much in dogma, I can assure you that 50 years ago if fellows had on hand diamond plates to use, they would have fooled around with them up, down and backwards and maybe even some would have used them as diamond nagura.

Alx

Alex, thanks! I'm going to experiment!

I am just enjoying the heck out of the #84. It's funny, but experimenting with different stones and techniques feels a lot like playing with legos when I was a kid! Simple pleasures....