Abstract: Irregularities in the outer surface of a commutator are identified and measured while the commutator is in the motor by removing a brush from its brush holder, and securing a jig in the brush holder. The jig has a sensor which generates electrical signals in response to movement of a profiling foot at an end of the sensor. The sensor is adjusted so that the profiling foot touches the commutator surface, and the commutator is then rotated at least one full revolution. By measuring movement of the profiling foot as the commutator turns, as observed through the output signals of the sensor, irregularities in the commutator surface can be identified and measured. The output signals of the sensor can be recorded or otherwise stored for analysis. The profiling foot is pivoted so that it rests flat against the commutator contacts, even if the brush holder is not properly aligned with the commutator.