The edge of the metal is finely ground after seal manufacture in a centerless grinder to enable an interference fit in the oil seal housing. A slight chamfer on the outer diameter (OD) of the seal is desirable for easy assembly. The sealing lip is prepared by buffing, grinding or cutting away the rubber flash which occurs at the sealing edge. A fine sealing edge creates sufficient pressure on the shaft to minimise spring load, leading to lower friction whilst maintaining effective seal performance. The garter spring plays an important role in the efficiency of the oil seal. If its tension is too high, heat will be generated between the sealing lip and the shaft, and result in rapid wear of the lip. If too low, the spring will be ineffective and the sealing lip will be worn away leading to leakage of the fluid.
For bisphenol-cured VDF/HFP/TFE polymers, calcium hydroxide level should be low and magnesium oxide level should be high to promote adhesion to metal inserts. Thermal black or mineral fillers generally give good adhesion.3 For most adhesive systems, it is necessary to limit postcure temperatures to about 200°C (392°F).3
A patent for an oil seal was filed by Nelson Thomas Edward on August 12, 1937, and published a year later. There were two purposes described. The device was to provide an oil seal between a fixed housing and a rotating part. The seal is described as