TWIST DRILL

摘要

A twist drill (10) including a cutting tip (12) having a front flank face (14), a substantially cylindrical tool body (16) extending rearwardly from the cutting tip, and a shank (18). The tool body (16) includes a rotational axis therethrough and at least one flute (20) formed on an outer peripheral surface thereof and extending to the front flank face (14). The at least one flute (20) includes a first helical portion (24) opening to the front flank face (14) and a second helical portion (26) extending from the rear end of the first helical portion toward the rear portion of the tool body (16). The second helical portion (26) twists in a direction opposite of the first helical portion (24).