| 摘要 |
A hollow drill is provided to enhance cutting performance of the hollow drill by forming a cutting segment having a tooth shape at an end portion of the hollow drill. A hollow drill(1) comprises a main body(3) and a cutting segment(2) formed at an end portion of the main body of the hollow drill. The cutting segment occupies about 40 to 80% of a circumferential surface of an end portion of the main body. Preferably, the cutting segment occupies about 50 to 70% of the circumferential surface of the end portion of the main body. The number of the cutting segment is determined according to the equation of Dxpix0.4/15 < x < Dxpix0.8/10, wherein D is a diameter of the hollow drill.
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