| 摘要 |
PROBLEM TO BE SOLVED: To provide a gun drill capable of high feed for improved machining efficiency, increased tool life during boring hardly cut materials and welding prevension during boring aluminum and copper materials. SOLUTION: A gun drill, wherein a cutting edge ranging from the outer periphery side to the inner periphery side of a tool is formed at the end of a tool body to be rotated about an axis O, consisting of an outer periphery cutting edge portion extending to the front end of the tool and an inner periphery cutting edge portion 11 extending to the rear end of the tool in the range over the outer periphery cutting edge portion at the inner periphery side of the tool, has a center cutting edge portion 15 formed at the inner periphery end of the inner periphery cutting edge portion 11 in such a manner as to be gradually set back from the inner periphery cutting edge portion 11 to the rear end of the tool as tending to the inner periphery side of the tool until it intersects the axis O.
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