| 摘要 |
PROBLEM TO BE SOLVED: To provide a core drill which prevents a cutting blade from colliding a workpiece with impact even when a center drill penetrates the workpiece. SOLUTION: The core drill A is provided with: a cylindrical base substance 1; the cutting blade 2 arranged at a tip end of the base substance 1 in a circumferential direction; a mounted part 1b to be mounted on a rotation driving device in a base end side of the base substance 1; and the center drill 5 arranged so as to penetrate a center of the cylindrical base substance 1 and protrude the tip end thereof ahead the tip end of the cutting blade 2. A tip angle forming part 5T with a tip end angleαis formed on the tip end of the center drill 5, and a tapered shaft part 5D with a taper angleβsmaller than the tip angleαand a boring blade 5d formed on an outer peripheral face is provided on a portion near to a base end with respect to a dead end of the tip angle forming part 5T. COPYRIGHT: (C)2009,JPO&INPIT
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