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The shaft surface upon which a high performance radial lip seal operates is the second most important element of a sealing system, second only to the seal itself. For many years the standard specification for shaft surface finish or texture was “0.25 - 0.50 μm Ra plunge ground with no machine lead”. Since this has been a costly and difficult process to create and control for many applications, other shaft processing methods have been used. This paper outlines the initiation of a study to evaluate the performance of radial lip seals on a variety of shaft surface finishes. The converter hub or front pump seal application has been selected for this study due to the unique shaft finishing processes incorporated.

In recent years, the methods for finishing shaft surfaces for radial lip seals have received greater attention. The standard surface finish specification, which requires 0.25-0.50 micrometres Ra with no machine lead and recommends plunge grinding, remains valid for only a portion of the shafts used in vehicular applications. Each finishing process requires its own specification. This paper evaluates paper-polishing for preparation of radial lip seal running surface finishes.