PURPOSE: To enhance the cutting force to the maximum by providing a rotation retaining ring in the center of rotation of a cutter arm of a right handle, disposing a cutter on a projecting piece, providing a rotation retaining ring accommodated in the rotation retaining ring of the right handle in such a manner as a freely rotate on a left handle and disposing a cutter on a projecting piece.

CONSTITUTION: A cutter arm 5 is formed on a projecting piece 4 of a right handle 1 extending counter-clockwise, and a cutter base metal 6 is inserted and fixed in the projecting piece 4. Secondly, A projecting rotation retaining ring 9 is disposed on a face of the cutter arm within 120° with the center O as the vertex. A rotating auxiliary piece 7 having the perimeter 8 with an adaptive radius is disposed in the lower half portion of the cutter base metal 16 and a facing right cutter 10 is disposed. Similarly, a cutter arm 13 is formed on a projecting piece 12 of a left handle 11 extending clockwise, a recessed rotation retaining ring 16 is disposed there, and a facing left cutter 17 is disposed. Subsequently, a portion of the cutter arm 13 is inserted in the cutter arm 5. At this time, the right half of the projecting rotation retaining ring 9 provided on both inner surfaces of the cutter arm 5 of the right handle 1 is accommodated in the recessed retaining ring 16 provided on both surfaces of the left handle 11.