One of the drawbacks of ceramic stones is that they are rarely flat. I used a diamond stone to flatten my extra fine (about 1800 grit) and my medium ceramic stone. It broke the glaze and left them slightly mottled. However, this does not seem to have affected their cutting ability and I continue to use them. This causes me to wonder if (1) I am deceiving myself that they cut as well as before and (2) if they can be flattened with a diamond stone why does the ceramic stone manufacturer not flatten them since it would make them more desirable? Anyone in this group tried what I did? Did it work for you?
They Should come flat from the factory. At least the shaptons I have are flat. I can't recall seeing any new stones which are not flat, though I haven't checked recently.
1800 is not really extra fine is it? I'd call something like 8000 extra fine.
I've heard of these Shapton stones and I do not believe they are true ceramic stones (fused through extremely high heat) but are really a type of Japanese water stone which use a different procedure for binding the abrasives than normal Japanese stones. I am not saying this with certainty and I could be wrong but I don't think so. Ceramic stones undergo intense heat and it's the heating that distorts them and makes it next impossible to create perfect flatness. I'm sure there are people who understand this a lot better than I do and I hope one of them will stumble across the thread and clear things up.
Why would you care if they are ceramic or not? . They sharpen great, are easy to get flat and don't dish like waterstones. The most important distinction between them and waterstones is that you don't soak Shapton stones. You use water to float away the debris. They should be used clean rather than with a slurry like a water stone.
Shapton calls them ceramic. Do you think they are lying? Why would they lie? Are they gluing this stuff together? I have some of these stones. If they are not ceramic it is not obvious what they could be.
The Japanese have a long history of ceramics and continue to research ceramic technologies constantly. It is not a stretch to say that they lead the world in this industry. When the US needed tiles to keep the space shuttle cool they went to Japan to find the man to do this. He came up with something light and highly heat resistant. Too bad they didn't spec something that was "big chunk of insulation" resistant as well. Ceramics can be designed to have a huge range of properties.
Here are some typical tolerances for industrial ceramic components.
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grinding, flatness is typically 6 thousandths of an inch. With grinding they can bring it down to 2/100,000ths.
6 thousandths over 8 inches is pretty flat. 2/100,000ths is well... really flat. There is no reason other than cost saving for a ceramic sharpening stone to be anything less than flat.
It is as absurd to state that it is impossible for ceramics to be flat as it is to state that it is impossible for steel to be flat. You mention that ceramics undergo high heat which distorts them. Um.... so does steel. In fact, ceramics distort much less under heat than steel. Silicon nitride has a co-efficient of expansion 1/6 of that of stainless steel.
Actually, I believe the US "went to" Seattle for the tiles:
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paragraph down). Perhaps someone can find a better reference.
Disclaimer: IANACE, but I know one.
OBWW: I recently made a picture frame from white oak to match an older one. A carefully made sled ensured excellent miter joints, even though this frame was approximately 30"x40". And in case he's actually reading this thread, Swingman might be interested to know that I went to some effort to adjust the sled so that it cut 45 degree miters (not simply complementary ones). :)
Some orange shellac will give a finish which closely matches the older frame, which isn't nearly as nicely made, I might add.
This is the second time I've used the "face frame" blade on my PC biquick joiner. It worked great.
Well, I thought I preferred the ceramic stones because they are impossible to wear out or dish, like all other stones I had used. Plus, they are fast cutters. I am keeping an open mind and will keep my eyes open for a Shapton stone. Still, it seems to me that these Shapton stones must dish because Shapton offers a device for keeping them flat.
Curiously, I am still looking for the answer to my original post, to wit, "Is there anything wrong with using a diamond stone to flatten a ceramic stone." My experience seems to be that there is not but perhaps I am missing something.
If you looked at the shapton device for flattening stones you would notice it is diamond impregnated. So, maybe you did miss that. Go ahead. Use whatever you want to flatten it. Anything flat and abrasive should work.
Shaptons are waterstones that use some sort of ceramic abrasive instead of whatever regular waterstones use. They wear hollow just like waterstones only more slowly, and should be flattened whenever they get too far out. Flattening them does not reduce the rate at which they cut.
Until Shaptons came along there was no confusion regarding "ceramic" stones. These are ceramic through and through (as opposed to ceramic grit in some sort of media). The coarse and medium grit ceramics are made to fairly rough flattness tolerance - 0.010" if memory serves. The fine grit ceramics are made to 0.001". They probably have to throw out a lot of them because fines cost twice as much as mediums or coarses. My understanding is that you cannot flatten a true (non-Shapton) ceramic stone without compromising its cutting ability. That observation was made during an old FWW review of various stone types.
To restore most of the cutting ability of a non-Shapton ceramic you scrub it aggressively with water, Comet, and a sponge.
I discovered, quite by accident, that auto rubbing compound cleans ceramic stones very quickly. No scrubbing, just rub it with a finger. Quick rinse, and Bob's your uncle.
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