Importance

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Abstract

An earth-boring bit has a bit body which connects to a drill string. Three cutters are rotatably secured to a bearing shaft of the bit and a large number of chisel-like cutting elements are secured to each cutter. Each cutting element has a cylindrical base and a cutting end. An elongate crest is located at the tip of the cutting end. A conical chamfer connects the crest and the cutting end. The junction created by the chamfer is non-tangential and reduces the amount of unsupported material at the crest. The conical contour of the chamfer is defined by by a straight line moving in an oval path about the longitudinal axis. The contour of the cutting end avoids abrupt changes and associated stress concentrations. This is achieved by avoiding surfaces of rotation in non-axisymmetric configurations. Alternatively, the contour of cutting end of element may be conventional and include flat surfaces, surfaces of rotation, and associated fillets and radii to soften the contour of the intersections between such surfaces. The chamfer reduces the sweep angle of the crest and the associated amount of material of the cutting element that is unsupported at a relatively low to moderate depth of penetration. Similarly, the amount of material of the cutting element left in tension and subject to chipping is reduced. The chamfer does not require modification of the radius of curvature of the crest, but alters the angle swept by the crest and the amount of material left unsupported.

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First Claim