ROLLING CONE BIT HAVING GAGE AND NESTLED GAGE CUTTER ELEMENTS HAVING ENHANCEMENTS IN MATERIALS AND GEOMETRY TO OPTIMIZE BOREHOLE CORNER CUTTING DUTY

摘要

A rolling cone bit (10) having a gage row (80) and an adjacent nestled gage row (70) 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 (60, 70, 80) 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 (70) will have cutting surfaces that are more wear resistant or harder than the cutting surfaces of the gage cutter elements (80) which experience more bottom hole duty. The nestled gage cutter elements (70) engage the borehole wall with a negative rake angle for increased durability. Preferably, the nestled gage cutter elements (70) have continuously contoured and non-shearing cutting surfaces.