Abstract: A brake lathe for truing brake rotors includes a tool holder driven by a direct current motor to move a cutting tool radially with respect to the rotor axis in direct proportion to the number of turns of the drive shaft of the direct current motor. A tool feed power control circuit maintains the direct current motor at constant speed regardless of radial forces acting upon the cutting tool and includes a converter/filter circuit, a regulator circuit, a sensing circuit, and a speed control circuit. A speed selection control includes a rheostat for providing a reference voltage corresponding to a select speed. The sensing circuit compares a voltage drop across the direct current motor to the reference voltage and produces an error voltage. The speed control circuit provides a direct current power voltage to the direct current motor in accordance with the error voltage output of the sensing circuit to maintain operation of the motor at constant speed.

Abstract: The invention is directed to a brake lathe having a device to eliminate or reduce vibration. Various types of dampers may be mounted on the arbor shaft of the lathe.