There is no standardized method for determining the load ratings of spherical plain bearings and rod ends, nor is there any standardized definition. As different manufacturers define load ratings differently, it is not possible to compare the load ratings of bearings produced by one manufacturer with those published by another manufacturer.
The basic dynamic load rating C is used, together with other influencing factors, to determine the basic rating service life of spherical plain bearings and rod ends. As a rule it represents the maximum load which a spherical plain bearing or rod end can sustain at room temperature when the sliding contact surfaces are in relative motion. The maximum permissible load in any individual application should always be considered in relation to the desired service life. The basic dynamic load ratings quoted for SKF spherical plain bearings and rod ends are based on the specific load factor K and the effective projected sliding surface. Values of K for the various sliding contact surface combinations can be found in table 1.
The basic static load rating C0 represents the maximum permissible load which may be applied to a bearing when there is no relative movement of the sliding contact surfaces. Values of C0 may be different for a spherical plain bearing and a rod end incorporating the corresponding bearing.
For spherical plain bearings the basic static load rating represents the maximum load which the bearing can accommodate at room temperature without its performance being impaired as a result of inadmissible deformations, fracture or damage to the sliding contact surfaces. The basic static load ratings quoted for SKF spherical plain bearings are based on a specific static load factor K0 (table 1) and the effective projected sliding surface. It is assumed that the bearing is adequately supported by the associated components of the bearing arrangement. In order to fully exploit the static load rating of a spherical plain bearing it is generally necessary to use shafts and housings of high-strength materials. The basic static load rating must also be considered when bearings are dynamically loaded if they are also subjected to additional heavy shock loads. The total load in such cases must not exceed the basic static load rating.
For rod ends it is the strength of the eye-shaped head of the rod end (housing) at room temperature under a constant load acting in the direction of the shank axis which is the determining factor. The basic static load rating represents a safety factor of at least 1,2 relative to the tensile limit of the material of the rod end head under the above conditions.