Abstract: An earth-boring bit for drilling a borehole comprises a bit body having a bit axis, at least two rolling cone cutters rotatably mounted on the bit body, a plurality of inner row cutter elements positioned on at least one cone cutter in a first inner row, a plurality of gage-cutting cutter elements positioned in a first fanned-gage row on a first one of the one cutters, and a plurality of gage-cutting cutter elements positioned in a second fanned-gage row on a second one of the one cutters, wherein the gage-cutting cutter elements on the bit define a gage curve and cutter elements in the first fanned-gage row and the second fanned-gage row contact the gage curve at different points. In one embodiment, each cutter element has an extension, and the extensions of the uppermost fanned-gage row cutter element and the first inner row cutter element define a step distance such that the ratio of the step distance to the extension of the first inner row cutter element is greater than 0.5.

Abstract: A rolling cone bit includes at least one cone cutter having a gage row of cutter elements and a first inner row of near but off-gage cutter elements that are positioned so as to divide the sidewall and bottom hole cutting duty so as to enhance bit durability, maintain borehole diameter and improve ROP. The off-gage distance of the first inner row of cutter elements is defined for various bit sizes to optimize the division of cutting duty. The distance that the first inner row of cutter elements are off-gage may be constant for all the cones on the bit or may be varied among the various cones to balance the durability and wear characteristics on all the cones of the bit.

Abstract: A rolling cone bit includes at least one cone cutter having a gage row of cutter elements and a first inner row of near but off-gage cutter elements that are positioned so as to divide the sidewall and bottom hole cutting duty so as to enhance bit durability, maintain borehole diameter and improve ROP. The off-gage distance of the first inner row of cutter elements is defined for various bit sizes to optimize the division of cutting duty. The distance that the first inner row of cutter elements are off-gage may be constant for all the cones on the bit or may be varied among the various cones to balance the durability and wear characteristics on all the cones of the bit.

Abstract: A rolling cone bit includes at least one cone cutter having a gage row of cutter elements and a first inner row of near but off-gage cutter elements that are positioned so as to divide the sidewall and bottom hole cutting duty so as to enhance bit durability, maintain borehole diameter and improve ROP. The off-gage distance of the first inner row of cutter elements is defined for various bit sizes to optimize the division of cutting duty. The distance that the first inner row of cutter elements are off-gage may be constant for all the cones on the bit or may be varied among the various cones to balance the durability and wear characteristics on all the cones of the bit.

Abstract: An earth-boring bit for drilling a borehole comprises a bit body having a bit axis, at least two rolling cone cutters rotatably mounted on the bit body, a plurality of inner row cutter elements positioned on at least one cone cutter in a first inner row, a plurality of gage-cutting cutter elements positioned in a first fanned-gage row on a first one of the one cutters, and a plurality of gage-cutting cutter elements positioned in a second fanned-gage row on a second one of the one cutters, wherein the gage-cutting cutter elements on the bit define a gage curve and cutter elements in the first fanned-gage row and the second fanned-gage row contact the gage curve at different points. In one embodiment, each cutter element has an extension, and the extensions of the uppermost fanned-gage row cutter element and the first inner row cutter element define a step distance such that the ratio of the step distance to the extension of the first inner row cutter element is greater than 0.5.

Abstract: A cutter element that balances maximum gage-keeping capabilities with minimal tensile stress induced damage to the cutter elements is disclosed. The cutter elements of the present invention have a non-symmetrical shape and may include a more aggressive cutting profile than conventional cutter elements. In one embodiment, a cutter element is configured such that the inside angle at which its leading face intersects the wear face is less than the inside angle at which its trailing face intersects the wear face. This can also be accomplished by providing the cutter element with a relieved wear face. In another embodiment of the invention, the surfaces of the present cutter element are curvilinear and the transitions between the leading and trailing faces and the gage face are rounded, or contoured.

Abstract: A rolling cone bit includes a cone cutter having a gage row and an adjacent nestled gage row of cutter elements that are positioned on gage so as to divide or share the borehole corner cutting duty. The wear resistance, hardness, toughness and shape of the cutter elements in the adjacent rows are optimized depending upon the type of cutting the respective rows perform, the characteristics of the formation being drilled and the drilling techniques being employed. In most applications, the nestled gage cutter elements will have cutting surfaces that are more wear resistant or harder than the cutting surfaces of the gage cutter elements which experience more bottom hole duty. The nestled gage cutter elements engage the borehole wall with a negative rake angle for increased durability. Preferably, the nestled gage cutter elements have continuously contoured and non-shearing cutting surfaces.

Abstract: A rolling cone bit includes a cone cutter having a pair of adjacent rows of cutter elements that are positioned so as to divide the sidewall and bottom hole cutting duty. The wear resistance, hardness and toughness of the cutter elements in the adjacent rows are optimized depending upon the type of cutting the respective rows perform. In most applications, the cutter elements experiencing more sidewall cutting will have cutting surfaces that are more wear resistant or harder than the cutting surfaces of cutter elements in rows experiencing more bottom hole duty. Likewise, the cutter elements exposed to more bottom hole duty will generally be tougher than those experiencing substantial sidewall cutting. The material enhancements include varying the grades of tungsten carbide used in the cutter elements and by selectively employing layers of super abrasives, such as PCD or PCBN. The cutter elements may be either inserts or steel teeth.