PURPOSE: To eliminate 2-stage fastening motion, by a method wherein a jaw is slid in an expansion and reduction state by means of a rotation nut, and slid in a pressed state by means of a fastening nut, and through rotation in one-way of a control cylinder situated between the two nuts, the rotation and the fastening nut are rotated in order.

CONSTITUTION: When a gripping ring 10 is held by a hand and a control cylinder 12 is rotated, through engagement of a torque piece 18 with a recessed groove 19, a resilient ring 17 is also rotated. Through engagement between a projected part 16 and a recessed part 20, a rotation nut 3 is rotated, and through the action of female and male screws 5 and 6, a jaw 2 is slid in a reduction inclination state to nip a tool C thereby. With the control cylinder 12 rotated, the rotation nut 3 is moved backward, and a bearing body 14 is pressed to bring a stationary ring 13 into pressure contact with a fastening nut 7. The fastening nut 7 is moved forward through the thread action of the female and male screws 8 and 9 as it is rotated, and a projected part 16 of a resilient ring 17 is moved over an engaging recessed part 20 and bent toward the recessed part 21 side. The rotation cylinder 12 is rotated in a state that the rotation nut 3 is in a rest state. In this case, a twist spring 24 is rotated, the rotation nut 3 is moved forward due to the presence of a gap R through the medium of the stationary ring 13 and the bearing body 14, and the jaw 2 is also moved forward and brought into pressure contact with the tool C.