The sliding frictional component of radial spherical plain bearing is consist of outer ring with inner spherical surface and inner ring with outer spherical surface. This kind of bearings is suitable for the machineries, which have low requirement of concentricity, and relatively big press on working surface with low speed sway, slant or rotary motion. There are mainly two kinds of sliding frictional component of radial spherical plain bearings: steel on steel radial spherical plain bearings and self-lubric.