clearance fit is adopted between the guide pillar and guide bush, with the quality of fit usually as H7/h5(G6/h5 or H6/h5 for high quality of fit and H8/f8 or H9/f9 for low quality of fit) and the slip length usually takes 1.5—2 times of the mating diameter, Whereas the remaining parts are countersunk to reduce friction, transitional fit is usually adopted between the mold plate and the guide pillar and guide bush, with the quality of fit as H7/k6 or H7/m6. In addition, to prevent the straight guide bush from falling off, a retaining groove can be applied to the flank of the straight guide bush, screwed with hexagonal socket head plug.