In this paper the strength of material based on the stressing in rolling contact is described. The investigations result in a guideline according to which the case depth of slewing bearing rings can be determined, if the load on the rolling elements, their size, and the number of load cycles are known. It is explained why the case depths should not be overdimensioned for manufacturing and strength reasons. Further discussions include the checking of the hardening, the influence of the soft section on the strength of the material, and the influence of the surrounding structure on the load distribution. An example illustrates that the stressing of the parts in rolling contact can be a multiple of the value calculated with a rigid structure if there are hard points in the surrounding structure.