Spherical roller bearings, inner rings have two raceways, and outer race-ways are spherical. The centers of curvature of outer raceways are also the bearing centers. The bearings possess self-aligning performance, the permissible disalignment angle is 1-2.5°,and can be used in certain permanent deflective application. These bearings are able to carry high radial loads, as well as axial loads at the same time , but not pure axial loads , the axial carrying bearing will be needed if axial loads were higher. The contact between rollers and raceways are so close,so the friction is higher than cylindrical roller bearings, and their limiting speed is lower. Spherical roller bearings are primarily used in such applications as rolling mills, paper making machines, power-driven gears , shipping and so on .