... BitCutting StructureThe durability of premium tungsten carbide inserts is improved with new formulas and new techniques for insert bit. Gauge ... BitCutting StructureThe durability of premium tungsten carbide inserts is improved with new formulas and new techniques for insert bit. Bearing ... 8",4",4 1/2",4 5/8",4 3/4",6",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 7/8",12 1/4",15",15 1/2",17 1/2 ...