| 摘要 |
<p>A nozzle structure for use in a rotary drill bit comprises an inner portion (36) which is formed with a passage through which, in use, drilling fluid may pass, and an outer portion (38) formed with an external screw thread (39) whereby the nozzle structure may be screwed into a corresponding internally screw threaded socket in a drill bit. At least the screw threaded outer portion (38) of the nozzle structure is formed from solid infiltrated matrix material so as to be resistant to erosion and damage. The inner and outer portions may be separate, integral or secured together. <IMAGE></p> |
