| 摘要 |
A twist drill including a cutting tip having a front flank face, a substantially cylindrical tool body extending rearwardly from the cutting tip, and a shank. The tool body includes a rotational axis therethrough and at least one flute formed on an outer peripheral surface thereof and extending to the front flank face. The at least one flute includes a first helical portion opening to the front flank face and a second helical portion extending from the rear end of the first helical portion toward the rear portion of the tool body. The second helical portion twists in a direction opposite of the first helical portion. |
