Abstract: The apparatus includes a drill motor and a cutter drive mechanism coupled with the drill motor for rotating and advancing a rotary cutter along an axial direction, and a clamping mechanism having a pair of opposed clamping members and an actuator that moves the clamping members relatively toward and away from each other for clamping and releasing a workpicce. The actuator is a fluid-operated cylinder such as an air cylinder, and a fluid circuit associated with the cylinder is arranged such that in a normal state of the fluid circuit the cylinder urges the clamping members together to clamp the workpiece. The apparatus includes a control valve that can be operated to cause the fluid circuit to control the cylinder to move the clamping members apart.