Diamond coring motors are used with Vac-U-Rig® and Dymorig diamond core rigs to drill holes into reinforced concrete. This 20 A model features 4.8 peak horsepower with a 300 rpm or 600 rpm operating speed. The 4079 uses a shear pin to protect gears and motor against overload. Shear pins are easily replaced and extra pins are included with the unit. This unit will handle core bits from 4 to 14 in diameter.