Hello,
I have a solid piece of granite, about 3/4" thick with a straight cut. Want to do a round edging myself, with grinder/sander type tool. I can get it to desired radius, but not sure how to finish it, to give more smoothness/ polish to match the top surface. I think I need to use various grades of sandpaper.
Not sure which.:eek:

That process is usually done with the proper tools for that procedure. i.e. wet saws, diamond bits, etc. Mostly done by special machines at a factory.

If you are a very handy person- meaning great with tool!! You may try to do it yourself.
Search the internet for diamond abrasives for granite edging. You will need a high speed hand grinder and lots of water. You may consider a dry method wich means using dry diamond abrasives but have to control dust. After your done with it you may have spent $200-$300 in abrasives and $200 for the grinder. I will be more cost effective to contact a granite fabricator or a stone restoration person to do this task for you.

Good Luck,
Willy
Specializedfloorcare