Abstract: In manufacturing an electric motor commutator which includes a cylindrical insulator having an axial bore for receiving the shaft of an electric motor, and a plurality of segments of commutator metal, such as, copper, extending about the outer circumferential surface of the insulator and being spaced apart by axially extending slots opening radially outward from the insulator between confronting surfaces of adjacent segments; the circumferential surfaces of the segments are shielded, as by plating the same with a metal other than the commutator metal, such as, silver, nickel, tin or zinc, or by coating such circumferential surfaces with a paint, whereupon, the resulting commutator assembly is oxidized so that only the confronting surfaces of the segments between which the slots are defined are covered with insulating layers of copper oxide, and then the shielding, along with any oxide that may have been formed thereon, is removed from the circumferential surfaces of the segments for exposing the copper or oth