We were always told at tech never to use ali any where near a grinding stone or wheel because it can clog the pores of the wheel ,expand and explode. This debate still runs today 35 years later but i still dont do it for that reason. A friend of mine was using a 4" grinder and for whatever reason the stone failed and took the top of his knuckle bone clean off. Kin ouch
There are special wheels made just for ali.
http://www.abtec4abrasives.com/cutti...nium-609-p.asp
http://www.finishing.com/317/17.shtml
Bob