| 摘要 |
This invention relates to a drill element (10; 11; 12) for percussion drilling, said element having a cylindrical screw thread (13; 14; 15) having one single entry. The screw thread, that is intended for thread diameters of less than 30 mm, has a pitch (s) of less than 12 mm, a shoulder angle ( beta ) of more than 21 DEG , and a pitch angle ( alpha ) of less than 11 DEG but more than 5.6 DEG . |
