| 摘要 |
A rotary drill bit comprising at least one rotatably carried roller cutter (17) and provided with passages (26,27,28) for supplying cooling fluid to the bearing system (11-15) of the roller cutter. For purposes of preventing the heat generated at an annular surface (31) transmitting axial forces from causing rapid bearing wear a recess (32) is provided in the annular surface (31). The recess (32) communicates with the passages (26,27,28) and extends entirely around the bearing shaft (16) for allowing circulation of cooling fluid therearound.
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