Diamond coring motors are used with Vac-U-Rig® and Dymorig diamond core rigs to drill holes into reinforced concrete. This 15 A model provides core drilling power where 20 A service is unavailable. This unit has a 500 rpm or 1000 rpm operating speed. The 4097-20 uses a clutch to protect gears and motor against overload. This unit will handle core bits from 1-1/4 to 5 in diameter.