| 摘要 |
Improvement in the drilling of vertical bore holes is achieved by an asymmetrical rotary cone bit having a substantially cylindrical body with a shank formed on the body and extending therefrom along a vertical axis for connection to a drill string. Projecting from the cylindrical body are three journal pins, which pins extend from the end of the body opposite from the shank. These three journal pins are circumferentially displaced such that the rotational axis of the first and second pins are displaced more than 120 degrees and less than 180 degrees. The axis of the third journal pin is circumferentially displaced equidistant from the axis of the other two journal pins. Journaled on the first and second journal pins are first and second roller cutter cones having substantially the same based diameter. Each of these cutter cones has cutting teeth extending from the surface thereof and includes a row of gage cutting teeth. A gage roller cone having a smaller base diameter than the first and second roller cones, is journaled on the third journal pin and includes a row of gage cutting teeth.
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