A positive feed tool includes a differential feed gear (138) and differential drive gear (136) coupled to a spindle (108) via a spindle drive gear (140) and a spindle feed gear (142) so that rotational drive and axial feed is imparted to the spindle during machining. In order to retract the spindle (108), the differential feed gear (138) is held stationary by pins (156) whilst the differential drive gear (136) continues to rotate. An apparatus and method is disclosed for automatically causing the spindle (108) to stop retracting. The tool includes a device which automatically moves the pins (156) or other members away from the differential feed gear (138) whilst the spindle is retracting, causing the spindle to stop retracting.