flatten a ceramic with DMT?

T

Talley1013

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Oct 15, 2010
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So I have been grinding away with my new 8" DMT continuous stones on some old POS kitchen knives and they are starting to break in. The DMT fine stone still doesn't give me as clean an edge as my $12 smith fine diamond but it is getting there. Obviously I can use the DMT XF for a finer edge but I have found that for my general purpose edc and work knives I prefer a finish in the 600-800 range.

Anyway, now to the question. I have a set of 3 spyderco ceramic bench stones(m, f, uf) that are pretty sweet for getting a crazy sharp polish but all three of them need flattening. The edges are higher than the rest of the stone. I can see evidence of this on the stone as well as the grind pattern on the blade. Can I use my new DMT stones to flatten the ceramic stones? If so what grit DMT is best for each grit ceramic? Will the DMT mess up the finish of the ceramic? I think I remember reading that the difference between the fine and ultra fine ceramic is how the stone is finished. I really appreciate all of your help. You guys have been great.

ET
 
I can't speak for the medium but the make up of fine and extra-fine are exactly the same. The fine stone is unfinished as it comes straight from being fired. The extra fine is surface ground after being fired. So if you flatten them with the same DMT stone, you will end up with 2 identical bench stones.
 
dsmegst said:
I can't speak for the medium but the make up of fine and extra-fine are exactly the same. The fine stone is unfinished as it comes straight from being fired. The extra fine is surface ground after being fired. So if you flatten them with the same DMT stone, you will end up with 2 identical bench stones.
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BINGO.

I flattened a Spyderco DoubleStuff hone (both sides, medium and fine) with the coarse (blue) side of a DMT Duo-Sharp hone. It got the job done. The DoubleStuff is nice, flat & smooth. BUT, there's no discernable difference in grit between the two sides now, so far as I can tell. On the one hand, that's a little troubling. On the other, I sort of like the extra smoothness of the hone. It's obviously not as aggressive anymore, but it's ability to polish an already fine edge is better now.

The other thing about flattening ceramic, even with a diamond hone, is that it takes a VERY LONG TIME. And I only did it to a pocket hone. I'd hate to think how long it'll take to do 2 bench-sized ceramic hones.
 
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I thought that ceramics and water stones being cut by diamonds can reach into the spaces between diamonds and dislodge them.
 
THG, that is correct but the bigger issue is the slurry. The slurry can create a suction between the stones and that's what disloges the diamonds. Excessive grinding pressure will do it too with the ceramics.

When I lapped my medium ceramic I found the XC plate to be the grit that didn't make it finer. It put some scratches in the surface but kept it around its original grit.

The fine grade of DMT plates are not for lapping and you can and will damage the plate. That said, the fine DMT works for lapping the UF ceramic, the fine ceramic I never lapped but I'd take a guess that the coarse stone would be the one to use.
 
THG said:
I thought that ceramics and water stones being cut by diamonds can reach into the spaces between diamonds and dislodge them.
Click to expand...

I've lapped two different ceramic hones on DMT hones. The first one was a UF Lansky hone (it was warped). I lapped it using an older DMT C/F Dia-Fold, which I'd previously not used much. I sort of went into that project assuming I'd either damage or ruin the Dia-Fold in the process. I leaned into into it pretty aggressively. It DID remove a lot of the diamond (visibly so), but to my amazement, it's still got a lot of sharpening life left in it. I actually use that hone a lot more now, than I had before I used it as a lapping stone.

The second ceramic I flattened on a DMT was the Spyderco Doublestuff hone mentioned earlier in the thread. The 8" Duo-Sharp that I used for that project fared much better (nowhere near as much visible loss of diamond). I approached this project with a lot more caution, using very light pressure on the hone as I lapped it. I also made sure I kept the surface wet. That Duo-Sharp was essentially brand new (one that I'd purchased years ago, but stashed away). I'd say now, the 'extra' wear I put on it with the ceramic hone amounts to the typical 'break-in' wear expected on these DMT hones. It's still in great shape. Perhaps even better.

I think Knifenut's estimation of the Coarse DMT being about right for the Fine ceramic, is pretty accurate. My coarse Duo-sharp left the white (fine) side of my Doublestuff hone in what I'd think of as 'new' condition for the fine side, maybe just a hair finer. As I mentioned earlier, it also left the 'medium' (brown) side in about the same condition. Live & learn... ;)
 
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