4. AN AUTOMATIC SHUT-DOWN DEVICE FOR DEACTIVATING A MACHINE TOOL INCLUDING A RECIPROCATING MACHINE ELEMENT AND AN ACTUATING ELEMENT THEREFOR, SAID DEVICE HAVING, IN COMBINATION, A MOVABLE BASE CONNECTED TO ONE OF SAID ELEMENTS, A GEAR JOURNALED ON SAID BASE FOR ROTATION ABOUT A PREDETERMINED AXIS, A RACK MESHING WITH SAID GEAR AND CONNECTED TO THE OTHER OF SAID ELEMENTS TO TRANSMIT MOTION FROM SAID ACTUATING ELEMENT, THROUGH SAID GEAR AND SAID BASE, AND SAID MACHINE ELEMENT, A LEVER FAST ON AND ROTATABLE WITH SAID GEAR AND TO EXTENDING RADIALLY OF SAID AXIS ALONG SAID BASE IN A PREDETERMINED ANGULAR POSITION, FIRST MEANS ACTING BETWEEN SAID LEVER AND SAID BASE WITH A PREDETERMINED FORCE AND YIELDABLY RESISTING ROTATION OF THE GEAR AND SWINGING OF THE LEVER IN ONE DIRECTION FROM SAID POSITION, SECOND MEANS ACTING BETWEEN SAID LEVER AND SAID BASE WITH A PREDETERMINED FORCE AND YIELDABLY RESISTING ROTATION OF THE GEAR AND SWINGING OF THE LEVER IN THE OTHER DIRECTION FROM SAID POSITION WHEREBY SAID LEVER AND SAID GEAR ARE HELD YIELDABLY AGAINST MOVING RELATIVE TO SAID RACK, AND MEANS FOR SENSING SWINGING OF SAID LEVER FROM SAID POSITION AS AN INCIDENT TO RELATIVE MOVEMENT BETWEEN SAID GEAR AND SAID RACK AND PRODUCING A SIGNAL INDICATING SUCH SWINGING.