Abstract: A reamer T including three-stage chip groups 6, each group having five chips 6 disposed circumferentially on a circle of a diameter smaller than an inside diameter of a hole H in a work W, axially at a given pitch P. When the axis Lt of the rotated reamer T is moved circumferentially on a circle about the axis Lw of the hole H after the reamer T is inserted into the hole H in the work W, the three-stage chip groups 6 simultaneously cut an inner peripheral surface of the hole H. When the reamer T is moved in the direction of pulling from the hole H by one pitch P in this state, the three-stage chip groups 6 simultaneously cut the inner peripheral surface of the hole H in the work W respectively by one pitch. Therefore, a boring work for providing the hole H having a depth D=3P in the work W can be completed in a short time.

Abstract: A thread milling cutter with drill blade has a drill blade 6 at the leading end of a land 5 divided by grooves 3 and a tapered tapping blade 7 provided behind the drill blade, with the upper end thereof in the direction of rotation projecting outward beyond the drill blade 6. The drill blade 6 first pre-drills a hole and then the tapered strong tapping blade 7 cuts internal threads on the inner wall of the pre-drilled hole.