The function of the skeleton oil seal is generally to isolate the parts that need to be lubricated in the transmission parts from the output parts, so as not to allow the leakage of lubricating oil. It is usually used for rotating shafts and is a kind of rotating shaft lip seal. The skeleton is like the steel bars in the concrete member, which acts as a reinforcement and enables the oil seal to maintain its shape and tension. Internal and external exposed skeleton oil seal. The skeleton oil seal is made of high-quality nitrile rubber and steel plate, with stable quality and long service life.

Other important factors are ensuring the hardness and roughness of the shaft are correct. A shaft hardness of HRC 45 is recommended for a rubber sealing lip, with a roughness of Ra 0.4-0.8. A higher shaft hardness of HRC 60 and shaft roughness of Ra 0.1-0.4 is recommended for a PTFE lip.

Cassette seals are designed to maximise grease or oil retention and protection against liquid or solid contaminants. These seals are provided with their own bushings in which dirt is kept out and oil/grease kept in by a multi-lip seal.

Oil seals are one of the major contact type sealing devices.
• They prevent leakage of the lubricant or other sealed substance, and
• prevent entry of dust and foreign matter (dirt, water, metal powder, etc.) from outside.

Figure 6: Recommended housing bore chamfers (shouldered bore)