I have some DA(1/4 inch coillet) grinders and a brand new IR 80 gallon compressor that I am itching to try out. I saw some grinding stones on ebay 50 for 20 bucks. I don't know if they are of high quality or not. I have used some cheap stones before and they just crumble and since the DA's spin free at about 20k rpm i don't want stones breaking off. Does anyone have a suggestion for a good brand of reasonably priced stones and where to get them?thanks