Importance

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Abstract

A drill bit sub, which has a drill bit with three equally angularly spaced cutters releasably threaded into its bottom surface, has its lower portion reduced in diameter. A collar is welded to the uppermost portion of the lower portion of the drill bit sub and has its lower surface formed at an angle to its longitudinal axis. A protective sleeve, which is a hollow cylindrical metal tube, is removably mounted on the lower portion of the drill bit sub and has its upper surface at the same angle as the lower surface of the collar. The protective sleeve has three equally angularly spaced wear strips, which are substantially aligned with the three cutters on the drill bit. A first break out ring is mounted between the bottom of the protective sleeve and a support surface on the drill bit so that the drill bit bears against the bottom of the first break out ring. The drill bit sub has its upper portion, which is beneath its threaded upper end threaded into a threaded receptacle in a lowermost drill section of the drilling tool, reduced to receive a second break out ring.

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First Claim