I have been having this problem lately where my DMT DIA-SHARP Coarse lapping plate started leaving a gray residue embedded in my Norton 4000. Interestingly enough, the plate is still removing material and lapping the stone. That said, it seems to me like the 4000 is working very poorly with the gray marks. I tried washing the plate with a dish-washing brush and soap to no avail. The DMT plate as been used to lap my stone quite a couple dozen of times so it is far from new.

I made a picture of the stone with the gray residue and also one from the plate. Is there anything I can do to prevent this? .... I heard the Atoma Diamond plates are pretty good at lapping. Maybe I should buy one to replace my funky DMT


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