PITCH MEASURING METHOD FOR COMMUTATOR

PURPOSE:To measure the pitch size between the commutator bar and the insulating material of a commutator highly accurately and continuously by combining and using an optical displacement gage and a rotary angle scale for the commutator. CONSTITUTION:In a commutator 1, commutator bars 1a and insulating materials 1b are alternately arranged in a ring shape. The commutator 1 is mounted on a rotary table 4. The rotary table 4 is rotated by a driving device 5. The rotary angle is read with an angle scale 3. An optical displacement gage 2 is provided at the outer surface of the commutator with a specified distance being provided. The distance to the commutator 1 is measured. The rotary table 4 is rotated, and the output of the angle scale 3 at a position where the output of the optical displacement gage 2 is suddenly changed is read. Thus the pitch of the commutator 1 is accurately measured.