| 摘要 |
A drill is provided to ensure a chip discharge space by gradually increasing the width ratio from a front end toward a rear end of a body of the drill, and improve stiffness of cut edges. A drill comprises a shank; and a body formed integrally with one end of the shank. The body has a front end with a cut edge, and an outer surface on which a flute groove is formed from a front end toward a rear end of the body. The body of the drill has a center where a web(116) is formed. The web includes a first web portion(120a) radially decreasing as it goes from the front end toward the rear end of the body of the drill, and a second web portion(120b) radially increasing as it goes from the extended end of the first web portion toward the rear end of the body of the drill. The flute groove includes a first flute groove portion and a second flute groove portion. The first flute groove portion is formed along the first web portion, and has a gradually increasing width ratio. The second flute groove portion is connected to the first flute groove portion and formed along the second web portion. The second flute groove portion has a gradually increasing width ratio.
|
