... formulas and new techniques for insert bit.Bearing StructureNon-sealed roller bearing. Drilling fluid can enter the bearing directly for cooling; Balls lock ... /8",4 3/4",6",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 7 ... Main Type Available Size: 6",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 7/ ... Structure Gauge protection with gauge inserts on the gauge surface of the cone, tungsten carbide inserts and hardfacing on ...