| 摘要 |
PROBLEM TO BE SOLVED: To provide a nonferrous metal machining twist drill which can suppress fusion during machining of a nonferrous metal, to thereby improve the service life thereof. SOLUTION: According to the structure of the twist drill 1, a radius R of a circular arc of a thinning base portion 8a1 is set in the range of 0.3 mm or more and 0.25 D or less, where D represents an external diameter of a cutting edge 5, and a chisel width X is set in the range of 0.02 mm or more and 0.2 mm or less. Further a surface roughness Rz of a thinning surface 8 is set in the range of 3.0μm or less. This structure contributes to synergistic improvement of the chip discharging performance of the twist drill. As a result, fusion due to deposition of chippings at the tip of the twist drill 1 is suppressed, and therefore the service life of the twist drill 1 is synergistically improved. COPYRIGHT: (C)2006,JPO&NCIPI
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