ROLLER DRILL

摘要

A rotary drill bit having a plurality of cutters, each rotatably mounted on a trunnion. The bearing support includes a friction bearing consisting of a cup member of half-moon shape preferably made of an oil soaked sintered material. The outer surface of the cup engages the bore of the cutter and forms the non-loaded part of the slip surface in the unloaded zone of the friction bearing. The cup is mounted in a manner retaining the cutter against axial displacement from the trunnion. Biasing means between the cup and trunnion presses the cup against the cutter bore and compensates for wear of the cup.