Group, At least some late Model 3996 1athes (two so far, one 1978 and one 1980) have a fourth bolt (not shown on the exploded view parts lists) holding the QCGB to the lathe. The fourth one is another 5/16" socket head cap screw similar to the two (one is hidden by the settings plate) at the top right of the box. This additional screw is in a hole through the top of the front way, visible and accessible inside the headstock after you raise the top cover. It is to the right of the small spindle gear and large back gear (NOT the bull gear). This screw is not shown on any of the dozen or so Atlas or Craftsman parts lists that I have, including the QCGB upgrade instructions. Could any of you who have one of the 1/2" bed machines look down in your headstock and see whether this screw is present or not? Report yes/no, model number and year of production (if known). Also, all 12" QCGB's should have a cast bracket attached to the inside of the GB main casting that sticks to the rear between the quadrant (banjo) and the left end of the headstock. The lower rear corner of the bracket should be visible if you open the change gear cover. There should be a bolt that goes through that corner and through the left rear corner of the left foot. On your machine, is this bolt inserted first through the bracket and then through the foot (bolt head visible below the quadrant) or through the foot and then the bracket (threaded end of the bolt and a nut visible)? Finally, is the bolt hex, square, or carriage head? Robert D.