Abstract: A tightening system for tightening a fastening member includes: a driving section producing torque for tightening the fastening member; an extension bar coupled to the driving section and rotating by the torque; a spindle to which the torque is transmitted via the extension bar and which is connected to the extension bar such that the spindle moves forward or backward in a rotational axis direction of the extension bar with respect to the extension bar; a socket provided at a tip of the spindle and engages in the fastening member; a spindle case housing the spindle and helically spline-engaging with the spindle along a rotational axis direction of the spindle; an outer case housing the spindle case; and a switch for switching between held and separated states between the spindle case and the outer case.

Abstract: A tightening system for tightening a fastening member includes: a driving section producing torque for tightening the fastening member; an extension bar coupled to the driving section and rotating by the torque; a spindle to which the torque is transmitted via the extension bar and which is connected to the extension bar such that the spindle moves forward or backward in a rotational axis direction of the extension bar with respect to the extension bar; a socket provided at a tip of the spindle and engages in the fastening member; a spindle case housing the spindle and helically spline-engaging with the spindle along a rotational axis direction of the spindle; an outer case housing the spindle case; and a switch for switching between held and separated states between the spindle case and the outer case.