Abstract: Air-operated, hydraulically controlled portable drill-countersink tool automatically clamping to workpiece. A spindle attached to drill is connected to gearing from a motor by helical splines to withdraw the spindle, to counter spindle-feeding force, responsive to encountering increased torque due to increased resistance in drilling or countersinking. In a hydraulic cylinder for collet clamping a lower air pressure is converted to higher hydraulic pressure. When drilling depth is reached, drill feeding changes to drill withdrawal and that change is triggered by blocking of an air vent by a member traveling with the spindle. A lower drill speed during countersinking is achieved by a valve reducing air supply to the motor and change in that valve is also triggered by blocking of air vent by a member traveling with the spindle. The blades of the air motor do not change in extension when loaded and the motor has constant torque.