Importance

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Abstract

A cutting structure for use in a rotary drag bit for downhole drilling is disclosed which relieves stress concentrations focused in the cutting structure along a line adjacent the surface where a cutting element abuts the carrier element or stud. A semicircular polycrystalline diamond compact (PDC) cutting element segment and a cooperating blank segment are diametrically bonded together and, in turn, bonded to a surface on the carrier element. The PDC segment has a chamfer formed along one inner edge, and the blank segment similarly has a chamfer formed along one inner edge. The two segments are joined together along their chamfered edges so that the chamfers are aligned to form a channel through the cutting structure when the segments are bonded to the carrier element. A groove may also be formed in the carrier element along the line where the polycrystalline diamond cutting element, the blank segment and the carrier element are joined, either in addition to or in lieu of the chamfers. The chamfers (and/or optional groove) thereby form a channel through the cutting element which relieves stress concentrations at the line of intersection of the cutting structure components. Another embodiment utilizes a carrier element with a shelf recess in which the PDC segment resides and no blank segment. The inner edge of the shelf or recess includes a radiused undercut extending within the carrier element, which undercut cooperates with the PDC segment chamfer to form the channel.

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First Claim