| 摘要 |
A drill is provided to pierce a hole in a work piece more easily and improve the precision of the hole by rolling and cutting the chip so as to reduce the piercing load and rotate at high speed. A drill(1) comprises a chip cutting groove(12) which is formed close to a cutting edge(11) to guide the bending of the chip cut out by the cutting edge(11), and a chip guide portion(13) formed in a straight or spiral shape in the longitudinal direction of the drill.
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