| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill which reduces a cutting resistance occurring at the time of drilling of an aluminum alloy, and smoothes flow of chips at a thinning portion to suppress welding at the thinning portion by specially designing the shape of the X-shaped thinning. SOLUTION: The drill having the X-shaped thinning 3 is a drill having an oil hole 5 formed therein, and designed such that a thinning bottom 8 is formed into a round portion having a size of 0.04 to 0.12 times a drill diameter, and that a thinning inclination angleαis set to the same as a drill twist angleβ. Further a drill groove length portion 7 is coated with a DLC coating amorphous film formed of TiC. COPYRIGHT: (C)2005,JPO&NCIPI
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