First, an elastomer, most often nitrile, is vulcanised to a metal ring. This creates a stiffening effect that includes a specialised metal tension spring directly behind the sealing lip, keeping the oil seal firmly in place against the moving part.
When the total eccentricity is excessive, the sealing edge of the seal lip cannot accommodate shaft motions and leakage may occur.
Total eccentricity is the sum of shaft runout and the housing-bore eccentricity.
Total eccentricity, shaft runout and housing-bore eccentricity are generally expressed in TIR (Total Indicator Reading).

What materials are available?
4. The sealing function of the oil seal is good and the service life is long. It has the certain adaptability to the vibration of the machine and eccentricity of the main shaft.
Oil seals close spaces between moving or stationary mechanical components to prevent lubricants like grease and oil from escaping, while also preventing dust, dirt, moisture, and other contaminants from entering the seal. Also known as shaft seals, dirt seals, lip seals, or grease seals, the primary components of any oil seal include an inner metal ring, which provides structural support, and a spring, which provides interference for effective sealing.
How are they used?
Figure 4.4. Scanning electron microscope (SEM) image of the surface quenched for (A) uncured rubber and (B) transmission electron microscope (TEM) image for cured rubber [64].
Standard 3760/3761
Fit the new gasket to the cover or head — whichever the old gasket was fixed to.