| 摘要 |
PROBLEM TO BE SOLVED: To provide a cylindrical drill capable of preventing a cutting blade of a cylindrical drill body from getting damaged due to rapid engagement with a material to be cut. SOLUTION: The cylindrical drill includes the cylindrical drill body having the cutting blade for drilling the material to be cut at its tip and a center drill provided along a rotation center axis of the drill body. The center drill has a small diameter part at the tip thereof and a large diameter part connected with the small diameter part via a shoulder. The small diameter part has a tip cutting blade at its tip, and the shoulder has a shoulder cutting blade provided so as to protrude forward the cutting blade. COPYRIGHT: (C)2008,JPO&INPIT
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