A Friction-Reducing Shaft Surface for Use With Standard Radial Sharp Lip Oil Seals

In the use of radial lip-type oil seals to seal against a rotating shaft, the surface characteristics of the shaft are important to the sealing and to the resultant seal/shaft friction. A plunge ground shaft surface with no lead has long been the recommended mating surface for a radial lip-type oil seal. Recently, however, a peened surface was studied which will reduce frictional torques a maximum of 50%, 60%, and 70% below that of one utilizing a plunge ground shaft surface for silicone, nitrile and polyacrylate seal materials, respectively. Seal performance from a leakage standpoint for standard sharp lip seals exceeds that of the plunge ground surface. However, the preliminary results indicate that the surface is not suitable with hydrodynamic shaft seals. Some insight into elastomeric friction was obtained from the tests. Surface characteristics which were shown to be important from a friction standpoint were asperity spacing (roughness width), asperity radius of curvature and asperity angle. The process was also shown to eliminate grinding lead on the shaft.