ROLLING CUTTER DRILL BIT WITH IMPROVED JOURNAL CONFIGURATION

摘要

A rolling cutter drill bit is disclosed which utilizes a plurality of rolling cutters each rotatably mounted on a lug member having a downwardly extending bearing journal. Each bearing journal has a ball bearing race formed therein for receiving a series of ball bearings which also seat in a mating ball bearing race formed in the rotatably mounted cutter. The ball bearings are arranged to share the axial loading placed on the rolling cutter and primarily lock the cutter on the journal shaft. Each journal is further provided with a unique large thrust surface across the downward end of the bearing shaft and generally perpendicular to the radial bearing surface. The large flat perpendicular thrust surface eliminates the need for a standard pilot pin structure normally found in rolling cutter bits. The elimination of the pilot pin structure allows the radial bearing surfaces to be machined in a more economic manner and eliminates the accumulated tolerances between concentric bearing surfaces which previously contributed greatly to cocking of the cutter on the journal and the resulting high stress single point loading which occurs from the cocking action of the cutter.