Abstract: To form a commutator segmental ring, an intermediate stage commutator ring (4) is formed from a flat strip (1) of commutator material which is bent into essentially cylindrical tubular shape to form a blank (2) having a gap or crack (3) adjacent the ends of the strip. The commutator ring, upon forming of the commutator, is severed into commutator segments. The gap or crack of the blank is aligned with a ridge or rib in a forming punch press to form a groove within the essentially cylindrical tubular blank (2) so that, when the intermediate stage commutator ring (4) is made, a cylindrical portion (5) already dimensioned for the intermediate segmental ring and a flange portion (6) are made, with a groove in alignment with the gap or crack obtained during cold-flowing of the metal in the press by the guidance afforded by the rib or ridge in the gap or crack of the cylindrical tubular blank.

Abstract: A die with bevel gear-forming cavity, a punch and a sleeve-like counter punch are constructed for press-forming cylindrical blanks. The punch has a diameter about equal to the circle defined by the intersection of the pitch cone with the low diameter bottom of the die cavity. The counter punch has a frusto-conical projection reaching in the cavity and is held until the die cavity is filled underneath, whereafter the counter punch retracts at a declining speed to fill the remainder of the cavity by radial flow.