Importance

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Abstract

The invention relates to the design of earth bore-hole drill bits embodying shaped preformed cutters containing hard abrasive materials, such as diamonds, the cutters being mounted in companion preformed sockets in the hard metal bit matrix. The extent of penetration of the preformed cutters into the formation being drilled is controlled by providing surface set diamonds embedded in the matrix at or adjacent to its gage portion, the surface set diamonds projecting from the matrix to a much lesser extent than the preformed cutters. As a result, the surface set diamonds can penetrate into the formation only to the extent determined by engagement of the adjacent face of the matrix with the formation. Although the preformed cutters project from the matrix to a greater distance than the surface set diamonds, their extent of penetration into the formation is no greater than that of the surface set diamonds.

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First Claim