Plain bearings are characterized as which?

• A. They use rolling elements to support shafts.
• B. They rely on a simple bearing surface without rolling elements.
• C. They require a fluid film to reduce friction.
• D. They are the same as ball bearings.

Answer: (B)

Plain bearings rely on a simple bearing surface with sliding contact, not on rolling elements. There’s no ball or roller inside; the shaft moves against a smooth bore or bushing, and lubrication is used to reduce friction and wear. This is why they’re distinct from ball or roller bearings, which use rolling elements to carry the load.

While some plain bearings operate with a fluid film (hydrodynamic or hydrodostatic lubrication) to further reduce friction, others use grease or dry lubrication. The defining feature remains the absence of rolling elements, not the need for a fluid film.