PURPOSE: To realize simple and quick operations for changing cutting blades and for controlling cutting edges by a method wherein an engaging edge, which fixes a cutting block to the position for changing the cutting blades or for controlling the cutting edges by sliding a locking plate to one direction and a releasing edge, which permits the cutter block from rotating by sliding the locking plate to other direction, are provided on the locking plate.

CONSTITUTION: When a locking plate 17 is moved on a frame 5 to one direction, an engaging edge 18 engages with the notch of the boss part 14 of a transmission wheel 7, resulting in checking the rotation of a cutter block 1. At the stopping position of the cutter block, the operation of bolts, with which the cutting blades are fixed, becomes possible and consequently the change of the cutting blades becomes possible. In addition, when the rotation of the cutter block 1 is checked by engaging the engaging edge 18 with the other notch of the boss part 14, the controlling of the cutting edges becomes possible at the stopping position of the cutter block 1. After that, in order to drive the cutter block 1 after the change of the cutting blades, the controlling of the cutting edges and the like, the locking plate 17 is moved to the other direction so as to release the engaging edge 18 from the notch and face a releasing edge 19 to the boss part 14, resulting in becoming the cutter block 1 rotatable.