| 摘要 |
The disc-shaped basic body (1) has a hole (3) through the center, and has circular ring-shaped segment-shaped cutting parts (2) around its periphery. In a peripheral direction, the cutting parts are interrupted by a cavity (4) passing through the cutting part in a radial direction and opening towards the outer circumference of the basic body. The basic body has at least one radially extending elongated hole (5) stretching along a section of a spiral ray starting from the center of the basic body. |
