Patent ID: 8034201

Claim:
An induction hardening method for hardening a steel member having an outer ring portion substantially in a shape of a circular tube with an outer circumferential surface and an inner circumferential surface surrounding a central opening and extending to a first axial end face, wherein the outer circumferential surface of the outer ring portion is hardened, the induction hardening method comprising: providing a first pressing member that includes a first substrate having an annular a flat first basal surface surrounding a first projecting portion provided at a central portion of the first substrate and projecting from the first basal surface, the first projecting portion having a cross-section in the shape of a circle and having an outer circumferential first pressing surface, the first pressing surface of the first pressing member being tapered so that the outside diameter of the first projecting portion becomes smaller toward a distal end thereof; pressing the central portion of the first pressing member into the central opening of the outer ring portion while initially maintaining a gap between the first axial end face and the first basal surface, so that at least a part of the first pressing surface presses against the inner circumferential surface of the outer ring portion; applying induction hardening, with induction heating, to the outer circumferential surface of the outer ring portion, while an axial force is applied to the first pressing member pressing it against the steel member; and continuing to move the first pressing member forward relative to the steel member, further into the central opening, to maintain abutment of the first pressing surface against the inner circumferential surface of the outer ring portion, as the outer ring portion thermally expands, while continuing the induction heating, until the first basal surface abuts against the first axial end face in parallel therewith.