A few years ago, I wrecked one of my diamond plates that I used for freehand sharpening. It’s a 3″ X 8″ plate with 400 grit on one side and 1200 on the other. The grit looked really uneven when it was new and it seemed that as I sharpened on it, the bits of grit that stood proud of the substrate would break off. I assumed that this was just part of breaking in the stones, but eventually the stones became less effective. I concluded that I was applying too much pressure.
The diamond grit is usually attached to the substrate with some sort of plating process – often nickel plating. It’s important to remember that the grit is not part of the substrate, but attached to it. Too much pressure (or a poor plating job) can knock the grit loose. Unlike a homogeneous stone, once the grit is gone, it’s gone.
When I first saw Clay stoning a blade in the promo video, a light bulb flashed in my mind. I realized that driving an edge into a diamond plate could knock grit off the substrate more easily than an edge drawn backward across the same plate at the same pressure. I now avoid drawing my diamond blocks down into an edge, except at very light pressure.
That said, I suspect the diamond bits in your case weren’t solidly attached and broke free. Perhaps a case of contamination somewhere in the plating process?
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