Drill with a tap, and the internally threaded processing method

摘要

Disclosed is a tap with a drill wherein three drill blades (26) and three threading edges (24) are respectively provided, three oil holes (28) are provided to penetrate in the axial direction, the core diameter (W) is set in a range of 0.25Dt-0.33Dt, a chip discharge groove (22) is provided with a negative land (22a) swelling into the groove, and since both the radial rake angle (Õ1) at the outer circumference of the drill blade (26) and the radial rake angle (Õ2) of the threading edge (24) are negative, a female screw (52) can be continuously cut practically while a rough hole (50) is cut under a state of being decentered from a hole-as-cast (46) by synergistic effect thereof even if the pressure of cutting fluid being supplied through the oil hole (28) is as low as 2 MPa or less.