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.
Basic dynamic load rating
The basic dynamic load rating C is used, together with other influencing factors, to determine the basic rating life of spherical plain bearings and rod ends. As a rule, it represents the maximum load that a spherical plain bearing or rod end can accommodate at room temperature when there is movement between the sliding contact surfaces (fig. 1
). The maximum load in any application should always be considered in relation to the required rating life. The basic dynamic load ratings quoted in the product tables are based on the specific load factor K table 1
and the effective projected sliding surface.
Basic static load rating
The basic static load rating C0
represents the maximum permissible load that a spherical plain bearing or rod end can accommodate when there is no relative movement between the sliding contact surfaces (fig. 2
For spherical plain bearings, the basic static load rating represents the maximum load that the bearing can accommodate at room temperature without inadmissible deforming, fracturing or damaging 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. To fully exploit the static load rating of a spherical plain bearing, it is generally necessary to use shafts and housings made of highstrength materials. The basic static load rating must also be considered when bearings are dynamically loaded and subjected to additional heavy shock loads. The total load in these cases must not exceed the basic static load rating.
For rod ends, it is the strength of the housing at room temperature, under a constant load acting in the direction of the shank axis, that is the determining factor. The basic static load rating represents a safety factor of at least 1,2 relative to the yield strength of the material of the rod end housing, under the above conditions.