A connection mechanism includes a rotatable member formed with a connection hole in which a shaft member is rotatably fitted. A thrust stopper is arranged at the distal end of the shaft member to prevent the rotatable member from being removed from the shaft member. The shaft member has an outer-screw at the distal end portion thereof, and the thrust stopper has an inner-screw opening extending along an axial direction of the thrust stopper. The outer-screw of the distal end portion of the shaft member engages with the inner-screw opening. The thrust stopper has a through opening formed with an inner-screw with which a fixing screw engages. The tip end of the fixing screw engages with the distal end of the shaft member to secure fixation between the thrust stopper and the shaft member.
