1. IN A MULTIPLE START SCREW MACHINE, A PLURALITY OF FIXED TOOL STATIONS EACH PROVIDED WITH A DEPENDING ROTATABLY DRIVEN CUTTER, A MEMBER MOUNTED FOR INDEXED ROTATION IN A PLANE BELOW THE CUTTERS, A PLURALITY OF COLLETS MOUNTED ON SAID MEMBER, MEANS FOR INDEXING SAID COLLETS IN REGISTRY WITH SAID CUTTERS, SAID MEANS COMPRISING A PLURALILTY OF STOPS FIXED TO SAID MEMBER, A STOP MEMBER FIXED WITH RESPECT TO SAID TOOL STATIONS IN THE DIRECTION OF ROTATION OF SAID MEMBER AND SLIDABLY MOUNTED FOR PORJECTION FROM A POSITION OUTSIDE THE PATH OF MOVEMENT OF SAID STOPS TO A POSITION OF INDEXED ENGAGEMENT WITH ONE OF SAID STOPS, MEANS FOR SIMULTANEOUSLY RAISING AND ROTATING SAID COLLETS WHEN IN SAID INDEXED POSITION, AND MEANS FOR CONTINUOUSLY MAINTAINING SAID STOPS IN PRESSURE ENGAGEMENT WITH SAID STOP MEMBER WHEN SAID COLLETS ARE IN AN INDEXED POSITION.