| 摘要 |
The objective of the present invention is to provide a drill capable of performing perforation with more proper condition, as to several workpieces such as a metal or a composite material. The drill according to an embodiment of the present invention has a cutting blade which has a shape that a line-symmetric and discontinuous line following a single or two parabolas or ovals is drawn on a projection plane, in case a passing area of a ridge in case of being rotated around a tool axis is projected on the projection plane in parallel with the tool axis. Moreover, the drill according to the embodiment of the present invention has a cutting blade with three or more different point angles, where position of each of both ends of a plurality of ridges forming the point angles are on a single or a plurality of parabolas. The drill according to an embodiment has a cutting blade with four different point angles, where a plurality of ridges forming the point angles border a single or a plurality of parabolas. |
