Patent ID: 8458902

Claim:
A method of forming a cam shaft by assembling a preliminary shaft having a predetermined outer diameter and a cam lobe including a cam-lobe shaft hole having a diameter larger than the outer diameter of the preliminary shaft, the method comprising the sequential steps of: (1) a first projecting-part forming step in which a first projecting part for fixing a first side surface of the cam lobe is formed on an axially predetermined position of the preliminary shaft by plastically deforming the predetermined position of the preliminary shaft upward and in a radially outward direction; (2) an inserting step in which the preliminary shaft is inserted into the cam-lobe shaft hole of the cam lobe from a side of the preliminary shaft on which the first projecting part has not been formed so that the first projecting part abuts the first side surface of the cam lobe; (3) a temporary fixing step in which the cam lobe and the preliminary shaft are temporarily fixed to each other, wherein a positioning member holds a second side surface and an outer circumferential part of the inserted cam lobe, and presses the first side surface of the inserted cam lobe against a side surface of the first projecting part which has already been formed on the predetermined position of the preliminary shaft by plastic deformation, such that the first projecting part is further plastically deformed, so that the cam lobe is circumferentially positioned with respect to the preliminary shaft and joined to the preliminary shaft in association with the two plastic deformations; (4) a disengaging step in which the positioning member is disengaged from the cam lobe; and (5) a second projecting-part forming step in which a second projecting part for fixing the second side surface of the cam lobe is formed on an outer circumferential part of the preliminary shaft near the second side surface of the cam lobe that was temporarily fixed during the temporary fixing step.