PURPOSE: To set a cutting width and the like by restricting the rotation of a main axis, and forming spacers between machine tools with primary spacers having external threads on the outer surface thereof so coupled as to be freely slidable in a lenghtwise direction and secondary spacers having internal threads on the inner surface thereof.

CONSTITUTION: A plurality of circular saw blades 2 are coupled to a saw blade axis 1 and monolithically turned and adjustable in a lengthwise direction with both keys 6. And primary spacers 3 are coupled to the saw blade axis 1 via internal threads on the outer surface thereof. Secondary spacers 4 have blades on the outer surface thereof and internal threads on the inner surface thereof, and are screwed into the primary spacers 3, thereby determining an internal between each of the circular saw blades 2. And a driving device 5 comprises a plurality of driving gears 9 on a spline shaft 8. After restricting the rotation of the saw blade axis 1, the driving gear 9 is rotated, thereby turning the secondary spacers 4 and dimensions between the edges of the primary and the secondary spacers 3 and 4 are changed. According to the aforesaid constitution, a cutting width or a machining width can be set properly.