Abstract: A method of forming flanged commutator segmental rings in a single power stroke by cold-extrusion which assures full formation of the inner ribs which become commutator segments, so that the segments will anchor well and resist centrifugal force at high rotational speed. The extrusion apparatus has an inner rib-forming die (18) and an outer ring-shaped flange-forming die (16). In the first stage of the power stroke, a ring-shaped blank (1) is formed into a flange precursor and a shaft portion (24) with inner ribs. In the second stage of the power stroke, the ring-shaped die (16) forms the flange (4) while the rib-forming die (18) forms a longer shaft (3) with a full complement of inner ribs (5) and a counter-punch (13) maintains pressure.

Abstract: A method for manufacturing commutator segmental rings, in which ring-shaped blanks (1) are transformed into commutator segmental rings. The method is carried out with a forming apparatus which uses a ring-shaped die (21) and a rib-forming die (25) to transform the blank (1) into a commutator segmental ring (2) with a flange (4) on its end and a shaft portion (3) with commutator segments (5) and cross pieces (7) connecting them. During the forming process, the die (25) moves against the force of an adjustable elastic counter-pressure apparatus (16; 13, 17, 19; 28). The counter-pressure on the facing side (24) of the upper punch (22), on which the die (25) fits, minimizes formation of a burr on the workpiece, and it permits use of a fastening means of reduced clamping power, thereby according the die (25) a greater pressure stability.