Most buffing is done at 3600RPM, while some, not all, grinders run at 1800. The nice thing with dedicated buffers is the extended shafts for working material around. A variable speed motor would be nice or if you have the space, maybe build a dual purpose belt drive version with a multi groove arbor, then you would have work around space plus the ability to change speeds, Baldor is the big name in buffing motors. Then there is the Eastwood/Harbor Fright "internationally built".