Which bearing type is most commonly used to support rotating shafts in light to medium machinery?

• A. Roller bearings
• B. Sleeve bearings
• C. Magnetic bearings
• D. Ball bearings (deep-groove or angular contact)

Answer: (D)

Choosing a bearing for rotating shafts in light to medium machinery comes down to speed, load, and reliability, and ball bearings provide the most versatile combination. Ball bearings, especially deep-groove or angular-contact designs, use rolling elements to minimize friction, supporting high speeds in a compact form. Deep-groove ball bearings handle radial loads with some axial capacity in both directions, making them a common general-purpose choice. Angular-contact ball bearings are built to take higher axial loads at higher speeds, especially when preload is used, which suits many machine components like motors, gearboxes, and spindles. This combination covers the typical service conditions of light to medium machinery, offering good speed capability, reasonable load capacity, and broad availability at a reasonable cost.

Sleeve bearings rely on sliding contact, which means more friction and wear at higher speeds and loads. Roller bearings can handle heavier radial loads but are more specialized and often less cost-effective for everyday light to medium applications. Magnetic bearings require active control systems and are costly, while ball bearings provide the best general-purpose balance for common rotating-shaft support.