Non-Ra Roughness Parameters of Shaft Surfaces for Radial Lip Seal Applications

For a long time, seal manufacturers and seal users have used Ra= 10 - 20 μin and machine lead <̱ ±0.05 degree to control shaft surface finish for radial lip seal applications. However, even when a shaft meets these requirements, the shaft finish may still be a cause of seal failure. In this research work, the deficiency of Ra is studied. The test data obtained in the work suggest that Rsk (skewness), Rku (kurtosis) and Rv (the maximum depth of the surface profile below the mean line) have the capability to separate the “good” and “bad” shaft surfaces for seal applications. The preferred value of Rsk, Rku and Rv parameters are recommended based on this preliminary study.