Thread: Scratches when using DMT 325 as lapping stone

At the advice of a very well respected source, I ordered a DMT 325 to lap my shapton 16K. It arrived a few days ago, and today (well, yesterday, technically) was the first time I cad a chance to actually use it. It certainly seemed to lap just fine, but it left a bunch of scratches and gouges in the Shapton, a couple of them deep enough to feel with the edge of my fingernail; I can't imagine that to be good for honing. Has anyone else had a similar experience? Am I doing something wrong?

Here are some picks, I rubbed pencil graphite over the scratches to make them more visible:

Before using a DMT325 to lap any hone, you should take a large screwdriver shank and run it vigorously across the plate to knock down any loose diamond bits. Once I did this procedure, I had no issues lapping my Naniwa Super Stones. However, I did run into some scratch issues a few weeks ago and had to redo this procedure again.

Too bad the Shapton DGLP costs nearly $400, but that is the lapping plate I would use if I had the coin for Shaptons.

That is super helpful, thank you!

I have abused the hell out of my dmt and there's stil one dang diamond scratching my hones.

Doesn't affect the edge, a good phrase I stole from someone; "Think of it as negative honing space, it's below the surface where the blade is riding."

If the screw driver does not work use some smooth concrete like in a basement.

Screw driver shank, hone a chisel or something similarly hard. Lapping a hard natural a bit can help too.

I was never happy with the scratches left behind by the DMT though. I know it's supposed to just be 'negative space' and not effect how they hone, but it bugs me all the same. So I typically wind up chasing the DMT with sand paper up to 1 or 2K depending on the stone, and I use my Naniwa red brick to refresh the honing surface when it gets clogged with swarf. No scratches, I'm a much happier camper.

Originally Posted by Marshal

Screw driver shank, hone a chisel or something similarly hard. Lapping a hard natural a bit can help too.

I was never happy with the scratches left behind by the DMT though. I know it's supposed to just be 'negative space' and not effect how they hone, but it bugs me all the same. So I typically wind up chasing the DMT with sand paper up to 1 or 2K depending on the stone, and I use my Naniwa red brick to refresh the honing surface when it gets clogged with swarf. No scratches, I'm a much happier camper.

I agree, as far as my naturals are concerned, particularly the slow and harder ones, need all the space I can get. Coticules just look better with a nice smooth surface, plus gouging out garnets gives me the willies

For synthetics, it bothers me a little, but i try to ignore it in favor of laziness

I usually use my well used 850 Smiths diamond hone after the 320 to take out the scratches, 1000 grit wet/dry on a hard surface would probably work as well

Thanks for all the suggestions! I sharpened on of my "rough work" knives on the DMT, then hit the Shapton again, and the result were much improved. I also adjusted the lapping technique a bit, favoring a very small lapping movement, and just letting the weight of the Shapton rest on the DMT, rather than pressing at all, which I think helped. It's a lot less aggressive, and probably will take a lot longer when I'm doing an actual flattening, but I guess that's the price I pay for getting a $50 not-really-a-lapping-plate rather than popping $400 for the actual Shapton plate. I can live with that.

“but I guess that's the price I pay for getting a $50 not-really-a-lapping-plate rather than popping $400 for the actual Shapton plate. I can live with that.”


No, you don’t need a $400 plate to lap a stone, most any flat diamond plate will work.

They all, even Atoma’s can use some smoothing out, sharpen a couple of knives, or bevel the edges of a stone or two to knock off any high diamonds, usually the edges.

I would not worry about your stone it will flatten out with time and refreshing. You can finish lap them with other lower grit stones.