Importance

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Abstract

A modular drill bit mounts legs within recesses in a body which are parallel to the central axis of the body using threaded studs with tapered outer portions, in conjunction with an attached pin having recesses therein receiving the upper ends of the legs. The lower ends of the legs terminate in spindles of open face configuration rotatably receiving cones thereon for rotation via a arrangement of bushings, roller bearings and thrust bearings, and a plurality of seals which slide and therefore rotate relative to both the leg spindle and the cone with the help of pressure compensating apparatus. Each cone is provided with cutting teeth which are inclined in the direction of cone rotation and which cover the cone surface in a manner which provides scraping of substantially the entire bottom surface of the hole being drilled and in a manner providing efficient scraping and crushing action. The cutting teeth are mounted in holes in the cone and then brazed in place, as are a plurality of ceramic buttons mounted within the extended portion of the cone to protect such portion and to provide backup gauging for a row of large cutting teeth mounted on an outer rim of the cone and having the cutting edges thereof inclined in alternating fashion.

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First Claim