To realize a structure capable of sufficiently restraining deterioration of flatness of an outside surface of a mounting flange 15 in press-fitting a male serration 18a formed on an outer peripheral surface of a stud 9 in a female serration 29 formed on an inner peripheral surface of a mounting hole 16a and to realize a manufacturing method capable of improving shape precision and surface precision of the female serration 29 and not producing chips in forming this female serration 29.

A dimensional relation forming a clearance between each of addenda and each of bottoms of both of the serration 29, 18a is adopted in a state of press-fitting the male serration 18a in the female serration 29. The female serration 29 is formed by plastically deforming the inner peripheral surface of a part in which a serration punch is pushed by pushing the serration punch into an intermediate part of a circular hole to be a prepared hole of the mounting hole 16a.