Big holes and wheels in wood, plastic, or soft metals are easy with these tools. Wheel cutters create a smooth disk, while circle cutters leave a ridge on the waste disk, and a smooth sided hole. Adjust depth of cut and diameter using the supplied hex wrench. Not for use in hand held drills. High speed steel cutter stays sharp longer, and cuts cleaner than ordinary tool steel cutters. Maximum safe speed is 500 RPM. Working range is 1" minimum diameter to 6" maximum diameter.