PURPOSE: To enable quick replacement of an blade edge and thus improve the working ratio of a machine by axially and rotatably fitting both ends of movable and fixed blades formed to have square cross sections to the tip part of shaft materials.

CONSTITUTION: Both end planes of movable and fixed blades 5 and 6 are pivotally fitted 8 and rotatably to the tip part of the end 7 of a shaft respectively. A male screw 11 is provided on the outer periphery of the end part of the shaft material 7, a nut 12 is tightened, and thereby the shaft material 7 is pulled. Through said procedure, the fixed blade 6 and the movable blade 5 are supported by and fixed to respective blade support members 3 and 4. When the cutting capability of blades 5 and 6 is deteriorated, the shaft material 7 is released by loosening the nut 12 and the blades 5 and 6 are rotated at about 90°