PURPOSE: To provide a driller adapted to allow the protection of a drill and a work with the returning of a drill by immediately halting the cutting the moment the torque works on the drill above the level of the normal cutting while the increase in the thrust resistance is detected.

CONSTITUTION: With the rotation of a work 2, a fine hole is drilled thereon with a drill 1 fixed or other wise it is done by switching the setting between the work and drill. When the cutting torque increases suddenly while cutting is performed with the rotation of the drill 1, the spindle turns against the tension force of the spring, hich actuates the limit switch to retreat the drill unit. When the thrust resistance increases, the spindle 3 retreats against the spring. Thus, a accident such as drill breakage can be prevented.