English: Model U600 ultrasonic drill, made by Vibro-Ceramics Corp., Metuchen, New Jersey in 1955. This could cut holes in glass, tungsten carbide, sapphire, ceramic, and hardened steel by ultrasonic machining, using a steel tool vibrating up and down at ultrasonic frequencies applied to the work with a slurry of abrasive. The power unit (right) produces an alternating current oscillating at ultrasonic frequency (above 20,000 Hz). This is applied to a piezoelectric ceramic transducer in the drill body (top) causing it to vibrate. The transducer is attached to an exponentially tapered steel rod (center) which acts as an acoustic "transformer" to increase the amplitude of the vibrations. The steel cutting tool is screwed to the lower end of the rod. A variety of interchangeable tools for cutting holes of various shapes and sizes come with the unit. The unit consumes 35 watts and weighs 15 lbs.