PURPOSE: To improve the blade edge height adjust precision and eliminate the need for skillful adjustment by achieving the means for positioning the knife blade bottom apart by using a space adjust bolt that is screwed to a fixing member and provided on the side of the adjust bolt.

CONSTITUTION: In a fixing method using an adjust bolt fixing member 20, an adjust bolt 12 is turned to adjust the height of the blade edge of a knife 10 to a specified height while the edge is directed upward. Then, using a space adjust bolt 26, the adjust bolt fixing member 20 is adjusted to a position substantially parallel to the blade bottom. After that, a fasten bolt 16 is fastened so that the head of the fasten bolt 16 presses the adjust bolt 12 while maintaining the adjust bolt fixing member 20 substantially parallel to the blade bottom. The adjust bolt 12 is thereby pressed and fixed while the advance-side flank of the adjust bolt 12 contacts the down-side flank of an insert threaded hole 14, so that the adjust bolt 12 will not bend if a large load occurs thereon during cutting. The height of the blade edge thus remains unchanged.