| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill capable of performing boring under more appropriate conditions with respect to various materials to be cut such as metal and a composite material.SOLUTION: A drill has a cutting edge having a shape causing axisymmetric and discontinuous lines along single or two parabolas or ellipses to be drawn on a projection plane when passage regions of edge lines are projected on the projection plane parallel to a tool axis in the case where the drill is rotated about the tool axis. Further, the drill has a plurality of different tip angles equal to three or more and has the cutting edge where positions of individual both ends of a plurality of edge lines forming the plurality of tip angles are on single or a plurality of parabolas. Still further, the drill has a plurality of different tip angles equal to four or more, and the plurality of edge lines forming the plurality of tip angles has the cutting edge brought into contact with single or the plurality of parabolas. |
