What are the main purposes of lubrication in bearings?

• A. To reduce friction and wear, remove heat, and protect surfaces
• B. To increase friction and wear
• C. To corrode surfaces
• D. To create more noise

Answer: (A)

Lubrication in bearings mainly serves to keep moving surfaces from rubbing directly together. A film of lubricant between the parts greatly lowers friction and wear because the surfaces never meet hard enough to grind or heat each other. It also carries away the heat produced by motion, helping keep temperatures in a safe range so the bearing doesn’t overheat. In addition, the lubricant forms a protective barrier that shields surfaces from oxidation, corrosion, and contamination, which helps extend bearing life. Depending on the bearing type and speed, the lubricant can also help support the load (through hydrodynamic or elastohydrodynamic effects) by creating a pressure film.

That’s why the option describing reducing friction and wear, removing heat, and protecting surfaces is the best fit. The other ideas—increasing friction and wear, corroding surfaces, or creating more noise—run counter to what lubrication is designed to accomplish.