you can get the diamond dresser tool they go buy the size not any thing to do with snap on and like i said looks to me it is old BD seat grinder.snap-on just put there name on it. so the stones have a 9/16-16 thread .any thing in auto machine tools and supplies are not cheap i buy some of tools and supplies on e-bay. every time you dress the stone turn the dresser a small bit this keeps it sharp .if you read thru what i posted and other you do not need the OLD MAN at some time you need to get the feel for the tools you have that comes with time