from the first component part 70 biasing the first component part 70 rearwardly such that the pins 78 and 80 abut the foward edges of slot 72 and 74 slots 90 and 92 formed in the frame 62 are arranged to receive shoulder screws 94 which are attached to the second component part 76 the interaction of the screws 94 and the slots 90 and 92 permit the composite slider 66 movement only in the direction of work feed referring to fig2 the second slider 68 is formed with a narrow slot 96 which extends angularly across the slider 68 starting on the left end near the upper edge of the second slider 68 and extending toward the center thereof terminating into a laterally enlarged aperture 98 the edge of the slider 68 opposite the slot 96 is formed with a cam protuberance 100 which extends outwardly from the slider edge at substantially the same angle as the slot 96 extends toward the center of the slider the second slider 68 mounts directly to the frame 62 using shoulder screws 102 through transverse slots 104 formed in the frame 62 the second slider 68 is so positioned on the frame 62 that the slot 96 containing portion of.