Tile drill bits, diamond hole saws, and diamond core drill bits can either be operated on a drill with a 3/8" or 1/2" chuck, or a variable speed grinder. Drills will typically be a single speed, ranging from 500-1,200 RPM. Running a diamond hole saw or core bit on a drill will cut material slower than a variable speed grinder, but are safe for operating most sizes up to 4" (maximum safe speed for 4" bits is 1,000 RPM). Variable speed grinders allow for faster cutting of material. However, when running a diamond hole saw bit or core bit on a variable speed grinder or polisher, the RPM you use will depend on the size of the bit. The optimal RPM for faster cutting for bits that are 1" or smaller is 4,000 RPM. The optimal RPM speed for bits 1-1/8" - 3" is 1,300-2,000 RPM. Standard 4" and 5" variable speed grinders start at 3,000 RPM, so if you have larger bits that require lower speeds, you may want to use a 7" to 9" variable speed grinder with a starting RPM of 600-900.