| 摘要 |
PURPOSE:To obtain a hole having a very fine finished surface roughness in one step, by forming chip discharging grooves of reamer and drill parts into a sprial shape in the same direction, and as well by forming a reamer edge having a specified angle with respect to the center axis thereof. CONSTITUTION:A combination drill consists of a drill part X, a reamer part Y and a shank part Z. A chip discharging groove 9 for a reamer edge 17 is formed in the same direction as the spiral direction of a chip discharge groove 6 formed in the drill part X. Further, the reamer edge 17 formed in the broach reamer part Y is formed at an angle of about 45-50deg. as its laid angle (theta-2) with respect to the center axis 11 along a margine 8 in a part other than the chip discharge groove 9 formed in the peripheral surface of the reamer part Y. With this arrangement, a drill hole having a fine finished surface roughness may be easily obtained in one step in a drilling process. |
