| 摘要 |
A drilling bit, such as a crenellated drilling bit for fluid-jet supported rotary drilling in rock comprises a nozzle for directing a jet of high-pressure fluid against rock material being bored. In addition to transporting away rock chips, the jet penetrates fissures in the rock and supports the breaking down of the rock structure by the drilling bit. Since such nozzles tend to wear more rapidly than the cutting edges of the drilling bit, a readily exchangeable nozzle insert is provided. The nozzle insert is seated in a retaining body incorporated in the drilling bit and is held in the retaining body by a threaded annular cap. The annular cap has a hexagonal recess for accommodating a tool such as an Allan-key.
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