When handle 1 is pulled downward, spindle 2, on which plug screw-thread gauge a is mounted, rotates so that the gauge is screwed into the workpiece. When handle 1 is released, weight 3 descends, turning spindle 2 in the opposite direction and screwing gauge a out 'of the workpiece. The mechanism is employed for checking small-diameter threads.
$3523$SFL,M$