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identify used laps

how cam I tell what grit diamond powder was used on these used laps? And how to clean thin?

The place or person you bought them from should be able to tell you,if not don’t buy.contaminated laps will cause many problems.

You can make a rough guess of what grit a lap has been charged with by cutting with it and comparing the “frosting” with a lap of known grit size. You should also be able to tell if the frosting is uniform or if there are scratches that indicate contamination…altho’ this might be after the sale. If you want to be absolutely sure of the grit, just recharge with a grit that is obviously coarser…altho’ this might not fit your needs. Another possible route would be to have the lap machined flat and have the machinist take a fairly big first cut, which should get under the diamond layer, keep him from dulling his tool and give you a lap that has no charge on it. This can only be done with a lap that is solid or has a thick top layer. Obviously not possible with plated laps. You should also look for any marks on the lap. It’s strange when people charge a lap and don’t write somewhere on it what they’ve done.

Thank you very much for your input. I was weary of buying used laps but the picture of the laps themselves forced my hand!