Abstract: A locking bolt that can reliably prevent loosening even when used at sites that experience severe temperature differences and severe vibration. The locking bolt (10) has a bolt main body (11), a diameter expanding member (31), and an auxiliary bolt (21). The diameter expanding member (31) is an inside the space (17) in the bolt main body (11) and has a truncated-circular-cone-shaped side surface (32) that comes into contact with the inner wall of the space (17) and expands the diameter of the space (17). The auxiliary bolt (21) is inserted into the axial hole (15) that is provided to the bolt main body (11), moves the diameter expanding member (31) in the direction in which the diameter of the space (17) in the bolt main body (11) is expanded, and imparts diameter expanding force to the space (17) in the bolt main body (11).

Abstract: A bolt capable of fastening without use of a special tool and which is extremely hard to be loosened (detached) after fastening is provided. A bolt of the present invention is configured by a fastened bolt, a fastening bolt, and a lock portion. A first engagement portion is provided on one end of a fastened bolt shank, and a concave portion is provided in the center part of the bolt shank. The fastening bolt has a second engagement portion on the surface confronting the first engagement portion and a fastening shank which is slidably inserted into the concave portion. The bolt is configured so that when the fastening bolt is turned in only one direction, the first engagement portion and the second engagement portion are engaged to turn the fastened bolt, but when the clamp load rotating the fastened bolt in only one direction reaches a predetermined torque, the lower strength portion is damaged so that the clamp load of the fastening bolt is not transferred to the fastened bolt.