| 摘要 |
PROBLEM TO BE SOLVED: To improve chip discharging performance of auxiliary chip discharge grooves, stably retain process tolerance with a high quality, and sufficiently secure a re-polishing margin of a peripheral cutting blade.SOLUTION: There are included: a drill body 1 rotated around an axis line O; a plurality of main chip discharge grooves 2 formed in the outer periphery of the drill body 1 at intervals in the circumferential direction; a peripheral cutting blade 4 along the main chip discharge grooves 2; auxiliary chip discharge grooves 3 arranged on the opposite side to the drill rotation direction of the main chip discharge grooves 2 in the outer periphery of the drill body 1; and an outer periphery finishing blade 5 along the auxiliary chip discharge grooves 3. A torsion angle of the auxiliary chip discharge groove 3 is larger than that of the main chip discharge groove 2 in at least one part in the entire length of the auxiliary chip discharge groove 3, and the auxiliary chip discharge grooves 3 are connected to the main chip discharge grooves 2 adjacent oppositely to the drill rotation direction of the auxiliary chip discharge groove 3.SELECTED DRAWING: Figure 1 |
