As far as cut-off wheels go, I get the longest and best service out of the 3M brand. I get 'em from a local auto finishing store, but you can get them from several sources. Do a Google search for them.
for the 3" cut off wheels in the die grinder I use 3M,they seem to last 3-4 times as long as any others I've tryed. for the 14" chop saw I use dewalt.
