Gear shafts often incorporate counter faces for radial shaft seal rings. Typical for these surfaces is the specification "ground twist-free". The so-called twist on counter faces for radial shaft seal rings (RWDR) can cause leakage. For example, the surface which is produced by turning with the typical kinematic roughness and spiral pattern creates a conveyor effect in the gap between the RWDR and the shaft. Depending on the direction of rotation leakage or dry running at the RWDR can occur which results in permanent leaking. Plunge grinding is a tried and tested manufacturing technique for creating twist-free surfaces. However, it has been established in the meantime that in spite of twist, rolled surfaces do not create a conveyor effect. The so-called "Fadentest" is not reliable for rolled surfaces; although this test can indicate this surface to have a twist, the service life and function of the RWDR are not impaired. This is due to the fact that a typical rolled surface does not show roughness peaks but wide plateaus which are interrupted by flat remaining valleys. This structure results in a high bearing line fraction. Substitution of grinding by hard turning and rolling can reduce costs for components of this type and shorten cycle times.
Gear shaft (Counter face to axial seal ring)