Which bearing component should not be lubricated in a typical maintenance scenario?

• A. Shaft
• B. Lubrication reservoir
• C. Mounting bolt
• D. Seal

Answer: (D)

The seal is not treated with lubrication in typical maintenance because its primary job is to keep lubricant in and contaminants out. Applying lubricant to the seal lip can alter clearances, cause swelling or degradation of the seal material, and lure dirt, all of which can create leaks rather than prevent them. Seals are designed to work clean and dry at the lip surface, while lubrication is directed to the bearing surfaces and the lubrication path. The shaft, lubrication reservoir, and mounting bolts all participate in delivering or receiving lubricant, so they are compatible with lubrication practices.