A metal tube with outwardly bent risers for terminals is filled with a body of plastic resin which hardens in place. Then the tube is cut through, chordwise, a plurality of times to provide a plurality of segments. An extended, base portion of the plastic resin body through which the risers extend radially outwardly continues to hold the cylindrical disposition of the metal segments, with gaps maintained therebetween. A shaft is fitted coaxially in the base portion of the plastic resin body and extends through a larger diameter central bore of the body, centrally of the commutator segments. The gaps communicate with the annular space between this bore and the shaft, for cleaning out of particulate debris by centrifugal force.