Abstract: A method of forming a helical internal gear by cold work, wherein a hollow blank is fitted onto a die on a mandrel, which is provided on an outer periphery thereof with a helical tooth profile and, while the blank is clamped and held in both axial directions thereof, a roller is pressed onto an outer periphery of the blank in a direction perpendicular to an axis of the mandrel while rotating the blank together with the mandrel, whereby the hollow blank is plastically deformed along the helical tooth profile on the die, and then a helical internal gear is formed on an inner peripheral surface of the blank.

Abstract: A method and apparatus for producing a stepped hollow component such as, for example, a gear blank. A solid slug, provided with a disc portion and a projecting portion, is placed in a rigid cylindrical recess formed between a counterpunch and a hollow mold. An annular upper surface of the disc portion and a side surface of the projecting portion are precompressed by an outer punch so as to restrain an outer periphery of the solid slug. A closed-base hole is formed in a center of the solid slug by a plastic deformation caused by an inner punch. The plastic deformation by the inner punch causes material of the solid slug to flow biaxially in the radial and axial direction of the solid slug.