Abstract: Quality control attachment adapted to be fitted onto a threaded depth control bar of a drill press machine includes a sleeve having an axial opening for fitting onto the control bar and being longitudinally movable relative to the bar. The sleeve carries a pawl and an elastic O-ring which urges an edge portion of the pawl into engagement with the threads of the control bar for enabling one-way movement of the control bar downwardly through the sleeve. An actuator pin is slidably disposed in a bore which extends through the sleeve and is movable downwardly in response to contact with a stop-nut disposed on the bar when the drill press has advanced to a preset depth represented by the position of the stop-nut.