containing a gear 148 the gear 148 is attached to an upper end of a threaded pin 150 the threaded pin 150 extends downwardly through the bottom of adjustment block 144 and through a threaded bore in a spacer block 152 the spacer block 152 is mounted between strips 102 104 of lower support arm 42 and corresponds to spacer block 64 of upper support arm 40 thus when the air cylinder 140 is actuated piston 142 adjustment block 144 threaded pin 150 and lower support arm 42 all move up or down together guide pins 154 fig8 are attached to table 68 and pass through holes in spacer block 152 so as to stabilize the lower support arm 42 and for mounting of support plate 164 adjustment of the lower support arm 42 is described with reference to fig8 and 11 a lower adjustment knob 160 and an adjustment pin 162 are vertically mounted on table 68 a support plate 164 is mounted below the table 68 and spaced therefrom the adjustment pin 162 passes through a collar 168 fixed to pin 162 through a hole in table 68 and through a hole in support plate 164 so that pin 162 is supported vertically and can rotate referring now to fig1 and 11 a drive gear 170 is fixed to adjustment pin 162 between table 68 and mounting plate 164 an elongated pinion gear 172 is mounted between table 68 and support plate 164 so as to mesh with gear 148 and with drive gear 170 when adjustment knob 160 is turned the drive gear 170 and pinion gear 172 cause.