Commutator maintenance tips and tests: Checking for loose bars and methods to tighten them
When servicing DC motors, one of the many tests we do to determine the condition of the commutator is to check it for loose bars. We check for loose bars by lightly tapping the face of the commutator with a very small hammer. Then we check for suspicious sounds and movement or vibration of the bars as they're struck. A loose bar will have a dull thud while tight bars will have more of a crisp "peck." You should not feel any movement of the bar with respect to adjacent bars. If the commutator is molded or riveted,it is not repairable and it should be replaced. However, V-ring commutators can be repaired.