Just a quick thought Stan. If you go with a disk grinder, you might consider a 9" disc. You can get precision, very true running disks with a 5/8" bore and standard 3/16" key. Then you can run it on a regular one and a half horse motor that you may already have around.
A huge reason to consider the 9 inch is that with cheap spray adhesive you can use standard 9" by 11" sheet paper. Once you stick it on, you just bring a shop knife to the edge of the disc and turn it by hand to trim the excess off. Goes on and off real easy.
The working area is big enough for jigged up pad contouring, but you get way more choices in abrasives with a much better cost. I think the 12" disc is a pretty narrow application woodworking tool that you may not have much other use for.
I'm not thinking it's a downgrade, a good disc is a solid tool. Only a thought is all.
