Importance

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Abstract

A tool, provided in the form of an up-drill sub, is comprised of a cylindrical body having a plurality of lobes integrally formed therewith and radially extending therefrom. Each lobe in turn is provided with a plurality of diamond cutting elements on an upwardly inclined surface of the lobe. The lobes are separated by channels or junk slots. The diamond cutting elements are arranged and configured on the sloping surface of the lobe to provide a cutting or reaming action as the tool is rotated and drawn upwardly in the bore. Tungsten carbide inserts are also provided on the circumferential gage surfaces of the lobes to provide gage protection. The ends of the sub are provided with selected pin or box connections in combination as appropriate so that the up-drill sub can be used anywhere within the drill string. Therefore, the up-drill sub may be used near the bit as a near bit or elsewhere in the drill string, such as a crossover sub between the drill collar and drill pipe or above a stabilizer. The outer diameter of the lobe of the sub are set at slightly less than the diameter of the bore so that no cutting action with the bore is affected unless a restriction or other imperfection in the bore arises which would prevent easy removal of the drill string and bit from the bore.

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First Claim