Abstract: A clamping tool for use with a stud bolt includes a tubular body formed on its inner periphery with first female threads adapted to engage a stud bolt and second female threads. A drive shaft is provided on its bottom end with a threaded shank adapted to engage the second female threads. A torque transmission mechanism is provided between the tubular body and the drive shaft so that they will come into engagement with each other when the drive shaft is turned in a direction to tighten the stud bolt and get out of engagement when the drive shaft is turned in the opposite direction. Thus the torque necessary to loosen the clamping tool to detach it from the stud bolt tightened in position is much smaller than the torque necessary to tighten the stud bolt.