Abstract: A rotary cutting tool is described which includes a motor for moving the tool vertically into a surface to be cut. The motor is connected to the tool by a clutch which is most preferably a ball clutch selectively engageable to transmit drive. The clutch further moves out of engagement should a force between two clutch members exceed a predetermined slip force. This predetermined slip force is adjustable by adjusting a spring force which is applied to maintain the clutch members in the engaged position.