PURPOSE: To finish the gearing surface of a bearing at a high accuracy by screwing and fixing a hub formed to one side rotator to the end surface of a shaft responding to a torque transmission shaft with a specific bolt fastening force, and after that, processing to finish the gearing surface of the bearing of the hub in a specific size.

CONSTITUTION: At first, a driving plate 4 is screwed and fixed to a dummy shaft 13 by a bolt 12. As a result, since the gearing surfaces 4f of the driving plate 14 are thin, they are deformed in the dotted lines in the figure. After the deformed gearing surfaces 4f are scraped by rotating the dummy shaft 13 to process in a specific size, the driving shaft 4 is removed from the dummy shaft 13, and installed as a flywheel 1. By fastening the bolt 12 to a hub 4b with a regular force, the flywheel 1 is screwed and fixed to a regular crankshaft 11. As a result, the gearing surfaces 4f of the hub 4b are deformed to eliminate the clearance between ball bearings 7, and the ball bearings 7 are made into a regular light fastening assembling.