During machining, especially when machining interconnected surfaces, the longitudinal, transverse, and horizontal positions of the flat jaw pliers on the workbench should be carefully calibrated in advance before planing.
(1) Correction of longitudinal position
Clamp a parallel pad iron in the flat jaw pliers, install a dial gauge on the tool holder, make the contact of the dial gauge contact the side of the parallel pad iron, and control the compression amount of the gauge at about 0.2 mm. Then move the ram and see if the pointer of the dial indicator swings. If the pointer does not move, it indicates that the longitudinal position of the flat jaw pliers is correct; If the watch needle swings, loosen the nut on the base of the flat jaw pliers, and then rotate the flat jaw pliers to adjust until the watch needle does not move.
(2) Correction of lateral position
Turn the angle of the flat jaw pliers over 90 so that the dial indicator still contacts the side of the parallel sizing block, and then move the workbench to adjust according to the swing of the needle.
(3) Correction of horizontal position
The horizontal position of the flat jaw pliers should also be adjusted in both the transverse and longitudinal directions. When correcting the longitudinal level, clamp an angle gauge in a pair of flat pliers to make the dial indicator contact contact with the upper edge of the angle gauge, and then move the ram to adjust. When correcting the horizontal level, place a parallel shim on the sliding surface of the flat jaw pliers body, and then contact the dial indicator contact with the upper plane of the parallel shim. Move the workbench and adjust it according to the swing of the gauge needle.