| 摘要 |
A rotary drill bit and drill bit cone for drilling bore holes through earth formations. The rotary drill bit includes a generally hollow body portion having a plurality of longitudinally extending shanks which terminate with inwardly directed spindles. A cutting cone is mounted upon each shank spindle and is provided with a plurality of elevated, primary, land areas which extend in a spiral pattern from the apex of the cone to the base. In a preferred embodiment, a plurality of elevated, secondary, land areas spiral from points intermediate the apex and base of the cone to the base of the cone in an alternate arrangement with the primary land areas. Cutting teeth are mounted upon each of the primary and secondary spiral land areas for digging into the earth formations during a drilling operation and in a preferred embodiment comprised partial disc shaped members which are embedded into the land portions of the spiral drill cone. A plurality of jet nozzles are mounted through the drill bit body and are generally directed between the shanks to project lubricating and cleansing drill fluid onto the rotating cutting cones and/or earth formation during a drilling operation. The maximum gauge of the drill bit is provided by an arcuate and annular enlargement zone fashioned generally at the base of each cutting cone. This zone enlarges the bore hole and facilitates vertical drill bit penetration.
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