| 摘要 |
The present invention is directed toward a drill bit which firstly comprises two locking grooves (1,1') diametrically opposed with respect to each other, and secondly, also diametrically opposed, with respect to each other, a first driving groove (3) and a second driving groove (4) associated with a locking groove (2) by being superimposed thereon. The driving groove (4) is advantageously angularly offset with respect to the associated locking groove (2) so as to have, in the drill bit driving zone, the lateral faces of the two associated grooves almost merged. This permits an extension of the friction zone so as to increase the wear resistance thereof, while the opposite lateral faces or edges of the superimposed grooves defines projecting locking surfaces (7) insuring proper locking of the drill bit. |
