| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill with a small diameter used for drilling a print substrate or the like and excellent in fracture resistance, and also to provide a manufacturing method for the same. SOLUTION: The drill is made of cemented carbide mainly composed of WC and Co. The drill has a blade diameter D of≤0.5 mm and includes a Co-reducing layer at least on the surface side of the blade groove of the drill and an circumferential part on the inner side. When Co content at the inner circumferential part is Co(i) (mass%) and Co content in the Co-reducing layer is Co(o) (mass%), the ratio of both Co(o)/Co(i) is≥80% and≤95% and the thickness of the Co-reducing layer is <10μm. COPYRIGHT: (C)2011,JPO&INPIT
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