The Diamond Products CB215 hand-held drill motor is a lightweight drill for coring up to 3-in. diameter holes by hand or up to 6 in. mounted on a core rig. This motor has a three-speed gear box ...

Also with safety in mind, Saunders recommends a hand-held machine for any holes up to 3 inches, and a drill stand or rig for larger holes. "Make sure the drill has enough power to drill properly ...