Abstract: Apparatus comprises a tool member (U) such as a sonic transducer, a fixture (F) for a workpiece, an anvil member (A), one of the members being stationary and the other being movable toward and away from the stationary member, a carriage (31) for the movable member, first means such as a piston rod (49) for holding the carriage up in ready position, second means such as a valve (VI) for releasing the first means to cause the carriage to descend to the workpiece, and third means such as a piston rod 51 for retarding descent to a velocity less than the free fall gravitational velocity. An automatic control system comprises sensing means, control relays and timing relays for activating the movable member, for energizing the tool member, for timing the period of energization, and for assuring dwell of the movable member in contact with the workpiece after the tool is deenergized.