PURPOSE: To fix a cam without dislocation in its fitting angle by providing a recessed part at the upper face of a rotation axis insertion hole of the cam, fitting an umbrella-shaped locating snap ring provided with cuts at its center hole and peripheral part into the recessed part and press-deforming the locating snap ring so as to be pressed to the rotation axis and the recessed part.

CONSTITUTION: A rotation axis 5 is fitted into the rotation axis fitting hole 1a of a cam 1. A recessed part 2 is provided at the upper face of the cam 1 so as to fit a locating snap ring 4 therein. The locating snap ring 4 in the shape of an umbrella is provided with cuts 4b at its center hole 4' and cuts 4a at its peripheral part, and formed of elastic material such as plastics. The angular position of the cam 1 is decided by an adjusting bar 6 and the locating snap ring 4 is press-deformed. The diameter of the center hole of the locating snap ring is made approximately the same as that of the rotation axis, but the diameter of the peripheral part is made slightly smaller than that of the recessed part. The locating snap ring thus formed is brought into strong contact with the rotation axis and the peripheral wall of the recessed part at the time of its press-deformation. The cam fitting angle can be thus prevented from being dislocated so as to obtain rigid connection.