Patent ID: 8448548

Claim:
A method of tightening bolts in which a plurality of bolts are tightened to a work by using a tightening head on which a nut runner is mounted, the method comprising: a bolt supplying preparing step of releasing a connection between a socket portion and an output shaft of the nut runner, and changing a posture of the socket portion to an upward posture in which a bolt holding portion provided at a forward end of the socket portion directs upward; a bolt supplying step of grasping one of the plurality of bolts held in a bolt magazine mounted on the tightening head by a bolt grasping mechanism mounted on the tightening head, and inserting the one of bolts from an upper side into the bolt holding portion of the socket portion by the bolt grasping mechanism, after the bolt supplying preparing step; a bolt tightening preparing step of changing the posture of the socket portion to a tightening posture in which the socket portion is laid along an axis of the output shaft of the nut runner, and connecting the socket portion with the output shaft of the nut runner, after a completion of the bolt supplying step; and a bolt tightening step of rotating the socket portion by the nut runner, and tightening the bolt held by the bolt holding portion of the socket portion to the work, after a completion of the bolt tightening preparing step.