| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill with an extremely small diameter used for machining nonferrous materials or steel materials whose service lifetime is improved by enhancing chip discharge performance while suppressing the wear of its tip cutting edge by coating it with a hard film. SOLUTION: The drill with an extremely small diameter is used for machining the nonferrous materials or the steel materials and has a blade diameter of smaller than 0.2 mm. A coated drill with an extremely small diameter is configured such that a chip discharge groove of the drill has a length of more than three times of the blade diameter, a base body of the drill is formed of ultrafine-particle cemented carbide in which the average particle size of WC is smaller than 0.8μm, and the drill is coated with the hard film of higher than HV 25 GPa. COPYRIGHT: (C)2008,JPO&INPIT
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