PURPOSE: To manufacture a small diameter drill without use of screws and improve the workability and productivity of the drill by fixing a blade part to a shank part by resiliency generated by motion of facing surfaces of a slit formed in a held part.
CONSTITUTION: When a blade part 31 is fitted in the direction of an illustrated arrow, facing surfaces of a slit 34 move relatively to each other by wedge action by angle θ1 of taper parts 31b to push a held part 31a to be narrower, and by further fitting it in, the upper end surfaces of holding parts 33a, 33b are applied to the right and left lower end surfaces of the blade part 31 to be fixed. By setting an angle θ2 to make taper parts 31c of the held part 31a parallel to each other and make the contact area of the holding parts 33a, 33b with both side end surfaces the maximum in this condition, the blade part 31 is jointed with and fixed to the shank part 32 by friction force. Because the upper end surfaces of the holding parts 3a, 33b are applied to the blade part 31, in addition, positioning of the blade part 31 to the shank part becomes secure.
MORI YOSHIKATSU
NOMURA TOSHIO
KITAGAWA NOBUYUKI
