Patent ID: 7371027

Claim:
A fastening tool comprising: a fastening body which is provided at its central portion with a shaft hole for the insertion of a shaft, including a slot groove in its axial direction, and having at its one of opposed ends of the slot groove with a bolt through hole formed with a seat surface, and at the other end with a threaded hole, and a fastening bolt which is inserted into the bolt through hole of the one end in the fastening body and is threadedly engaged with the threaded hole of the other end to fasten the fastening body in the circumferential direction, wherein: the seat surface of the bolt through hole in the fastening body is a conically tapered seat surface formed in a tapered groove, the fastening bolt includes a rod-shaped bolt body provided at its outer periphery with a male thread, and a head which is provided on an end of the bolt body and which has a diameter greater than that of the bolt body and which abuts against the seat surface of the bolt through hole in the fastening body, and a lower surface of the head is formed into a convex arcuately tapered surface whose diameter is reduced toward a tip end of the bolt body, and, wherein the arcuately tapered surface of said fastening bolt is an outwardly curved surface, and the fastening bolt is threadedly inserted into the fastening body whereby the outwardly curved surface of the arcuately tapered surface is in contact with the tapered surface of the fastening body.