XR series has two columns in into a 90 ° v-tapered roller holder vertically staggered through interval on the hob surface, able to withstand radial loads, axial loads and other loads in all directions. Raceways and rollers on the structure line contact provides maximum running accuracy, high stability and a greater degree of tilting stiffness. Preload adjustable design extends bearings life, increases in the maximum stiffness and provides minimal beats. Nylon spacer lower inertia, running torque is smaller. Or if electroslag remelting of components using surface carburizing steel bearing steel, good impact resistance.