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Lapidary Shop / Moderator, Catmandewe ( Tony ) / Discs, Wheels, Belts, Pads, and Polishing / Re: Coarse finish from 1200 diamond flat lap?
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on: August 16, 2015, 11:35:28 am
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Danny, thanks for the info. I'm glad to hear I'm not crazy. You're right, I didn't see or feel any unevenness. Is it only 1200 grit, or does that happen to finer (or maybe all?) diamond on metal?
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36
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Lapidary Shop / Moderator, Catmandewe ( Tony ) / Discs, Wheels, Belts, Pads, and Polishing / Coarse finish from 1200 diamond flat lap?
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on: August 16, 2015, 10:47:52 am
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I wanted to try to make the surface of a an agate cab flat, I mean glass-flat, and found that the softer discs I use on my Ameritool flat lap always gave a slight curve to the surface no matter how careful I was. So I purchased a 1200 (twelve hundred) grit metal diamond topper, thinking that would stiff and just aggressive enough to flatten any curves on a partially-worked stone, but not so coarse as to set me back to the grinding phase. But it's not working at all, and I am hoping someone might have some insights. Whenever I get a new abrasive I first use a small polished glass floor tile (from sheets @ Home Depot) to test out the surface. It gives me an idea of the actual abrasion level and also checks for defects before I get to my real stones. Imagine my surprise when my new 1200 grit lap scratched similar to a 180 (one-eight-zero) grit belt! I examined the flat lap surface carefully under magnification, cleaned everything and checked for contamination. Everything looked fine so I tried again but got the same results. Thinking there might be a break-in period I ran several different junk stones then started with a new tile, but again, same result. That can't be right, can it? I've searched this forum and saw a thread from a few years ago ( http://gemstone.smfforfree4.com/index.php/topic,13906.0.html) where Carol M had some scratching problems and the difference between paper-SiC vs. diamond-metal was mentioned, but I couldn't see any definite conclusions. (But I now agree with Carol's "*&^%$ SCRATCHES" assessment. :-) ) Nor did anyone suggest that 1200 d-m would compare all the way down to 180 SiC. Any thoughts on what's happening here? What am I missing?
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