PURPOSE: To change the geometric shape of the partially fabricated item of the drill by the same dies and with a little expense by constructing the dies from plural ring disks, and by a mechanism that the ring disks are relatively rotatably and fixably in a position constructed to adjust a helical angle.

CONSTITUTION: The ring disks 10a can be arbitrarily interchanged by the dies 10 combined from the individual ring did 10a, and the ring disks 10a can be relatively rotated. Consequently, a possibility of a lot of combinations for constructing the dies, is already obtained from a small set of the ring disks. Especially, not only arranging an arbitrary number of the ring disks 10a before and behind but also meeting a required length of the die, become possible. By rotating relatively the ring disks 10a each other, a rib provided on the inner peripheral wall of the die 10, is properly shifted, and a helical pitch is changed.