Do new Micro Fine Ceramic Stones (1.4 and .6 micron) need to be lapped?
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This blog post explains some of the differences between the ceramic abrasives and whetstones like the choseras. It is worth the read.
When I got started, I believe there was only one ceramic pair. It was labeled fine/micro-fine; now labeled 1.4micron/0.6micron. The 1.4 side is white and the 0.6 side is a dark grey or dark brown color stone. This pair 1.4/0.6 were supposedly made by the same maker as makes the stones for the Spyderco Tri-Angle Sharpmaker. These stones are super hard and worked very well, if you have experienced a Sharpmaker. I found this pair to work very well, for me, just as they came from WE. There’s some back and forth, on-going opinions, as to where in the sharpening progression they should belong. Apparently there’s more than one grit scales to describe their coarseness and particle size.
The 1200/1600 stones, I believe came along a little later. I believe these are ceramics also. Both stone sides are white. As they came I didn’t care for the feel of these stones or the results I got. I heard they had a sintered coating on the stones; like a powdery film. For me that inhibited the stone from making good flat contact with my knife edge, so I got an uneven scratch pattern. When I looked at the used ceramic stones face, I saw this same uneven skipping looking scratch pattern.
When I lapped them (1200/1600) the first time, I did it, they behaved as TCMeyer describes, as though they were the same grit as what ever was used to lap them. It was thought the lapping material scratched the ceramic’s surface and left a scratch pattern that was in turn transferred to the knife you used the ceramic to sharpen. After some time when the 1200/1600 wore in they improved, marginally.
Recently I lapped the same 1200/1600 set again, this time with a Shapton’s Diamond Glass Lapping Plate. It was a very hard job to do that. The ceramics are very hard. End result was two different grit ceramics stones, that behave as you’d expect they should. One is fine and the other one finer. They now have a narrow regular scratch pattern very similar in size, spacing and depth to what I see from the new 1500 Diamond Stone. The ceramics are not as aggressive as the diamond stone. Now that they’re surface is clean and flat I believe they behave like the grit rating describes and they do fit into the stone grit progression. They’re still different like every different cutting medium is, so they don’t exactly follow a straight line on the grit progression chart.
Marc
(MarcH's Rack-Its)1 user thanked author for this post.
Interesting blog article. So it seems that I have probably change my 1.4 and .6 micron ceramics to 1500 grit ceramics? And probably wore down my diamonds some. Oh well.
As in you may have done more damage to your diamond stones than you helped your ceramics.
I’m actually a little surprised by Clay’s experiences lapping a 0.6 micron ceramic. I had a completely different experience, but I don’t have a 3 micron lapping stone. I have to use sheets of diamond film and never got my ceramics back to where they were. But from what I’ve seen, yes, you can restore to their original approximate grits.
I would like to make a comment here that I think you guys are way overestimating the importance of the flatness of the stones. As they come from Wicked Edge, they are capable of producing very high quality edges. You can do much more damage by way of poor technique. Stick the best AngleCube you can find on the back of your “suspect” stone and watch it as you move the stone up or down the rod as it lies on the edge of a blade. Keep your finger pressure constant and at the bottom of the stone and you won’t see any angular change that would merit a lapping job intended only to flatten the face.
This is not to say that there aren’t stones out there that are bad enough to need repair or that ceramics are in the same class as film in terms of uniform scratch patterns. Ceramic stones are apparently cast and therefor have some surface texture variability. They serve a purpose.
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My experience with the 1200/1600 and the 1.4/.6 ceramics have been quite good for me. The stones seem to get better with use, after 30-35 knives with them I think they are still getting better. When I do use them I have to do 2,3 or 4 times the passes that I do with diamond stones. I personally would not lap mine, but there are a lot of more experienced artisans out there.
The 1200/1600’s are still getting better with use, and the same, all though not to the same degree, with the micro’s. The micro’s give me a very good cutting edge, very refined, but I sharpen more for function than for mirrored bevels for the most part. I use them for my final stones and don’t strop that edge very often.
I have noticed that it is very difficult to remove the scratches from any previous stones. They don’t cut nearly as fast, and don’t remove much metal at all, thus the extra strokes. They do require me to take more time when I use them but for certain knives they work very well as they came, for me at least. I do have to clean the ceramics with a super eraser every time I use them and sometime during use. Whatever metal does come off seems to stay with the stone for the most part I believe thus the cleaning.
Also the ceramics being as hard and fine as they are, are much more susceptible to foreign material trapped between the stone and the blade. If not strictly controlled this will drive you nuts and make you think there is something wrong with them.
These are some of my experience with these stones.
Thanks for your compliments on my blog article, Rich. Yet I would not recommend lapping ceramic stones, unless it is really necessary (because they are uneven or have clusters of ceramic material that cause scratches). In that respect I agree with Tom (Tcmeyer). I also wrote a blog about how ceramic stones work, which is quite different from whetstones or diamond stones: https://moleculepolishing.wordpress.com/2013/08/08/the-mystery-of-the-spyderco-and-the-wicked-edge-ceramic-stones/ and what lapping them with a diamond stone may do to them.
The conclusion is that lapping ceramic stones with a diamond stone may change their “grit” rating, so be warned.
My experience is the same as that of sksharp: after a couple of knives (sometimes quite a few) the stones get more even and clusters of ceramic material that cause scratches disappear. The stones get better with use.
Molecule Polishing: my blog about sharpening with the Wicked Edge
I’m not sure Sal will even be able to answer that. The stones that Spyderco uses are made by Coorstek, the same manufacturer that makes our Micro-Fine stones. I dug up the SEM photos that Coorstek sent me when we first got started after I badgered them for a while about the grit. They originally gave me grit sizes of 1.4µ for the brown stones and 0.6µ for the white stones. I asked for more detailed information, which is when they sent me these images and explained that because the grain sizes vary so much as a result of the sintering process (they’re essentially melting and forming new structures), they prefer to grade the stones by Roughness Average (RA). They also explained that the surface texture can be changed and tuned through lapping and that the new texture creates a new RA for the stone, which will last a fairly long time before the peaks are eventually worn flat again. You’ll see that the grain size is a lot larger than the stated grit size:
I’ll look around for data sheets on each stone.
-Clay
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