| 摘要 |
The tool has an elongated body (2) i.e. cylindrical rod, whose one end is provided with a pyramidal work head (4). The work head has concave work surfaces (6) that are distributed around a longitudinal axis of the tool. The work surfaces converge towards a tip (5) situated on the longitudinal axis, and are obtained in a helical manner, along the longitudinal axis. The work surfaces are connected with one another along helical edges (7) that converge towards the tip situated on the longitudinal axis. |
