| 摘要 |
PROBLEM TO BE SOLVED: To provide a drilling male blade enhancing drilling force without increasing length in the axial direction of an entire drilling male blade and exactly carrying out drilling.SOLUTION: The drilling male blade 5 has a circular shape in a plan view in the direction of a center axis M of a circular through-hole to be drilled and is symmetrical about the center axis M in a side view in a plane direction including the center axis M, and includes a tip protrusion 1 to be a trigger for drilling, a basic blade 2 continuous with the tip protrusion and having a large angle to the center axis M, a curved part 4 continuous with the basic blade 2 and curved to decrease an angle to the center axis M for reducing cutting resisting force that gradually increases by drilling, and a blanking blade 3 continuous with the curved part 4, including the curved part 4, and allowing a left part and a right part to be coupled at a tip end part. |
