Dave:

I'll stand corrected on the granite. The only stuff I've seen close up is my kitchen counter. I assume that like anything else, there's a range of quality and precision to be had. If it's good enough for machinists, then it ought to be good for sharpening, eh? Now that I think about it, sharpening and machining sound kind of similar...

Which system my paper is rated in? I guess I really don't know. The coarse grits I just pick up at the hardware store. The finer stuff at the auto parts store (a little more expensive). It's all 3M, wet or dry silicon carbide. I once had an isntructor tell me that the grit system is different than for stones. That's all I can tell you. It sounds like you know more about it that I do. CB.