What is the primary purpose of a bearing in a rotating assembly?

• A. To increase rotational speed
• B. To seal against leakage
• C. To transfer torque between shafts
• D. To support rotating elements and reduce friction and wear

Answer: (D)

Bearings in a rotating assembly are there to carry the loads on the shaft while letting it turn with as little resistance as possible. They support radial and axial forces and keep the shaft aligned so that gears, belts, or pulleys continue to mesh correctly. The main advantage is reducing friction and wear by providing a low-friction interface—whether through rolling elements or a lubricated film—so surfaces don’t grind against each other and heat generation stays in check. Seals and torque transfer are handled by other parts of the system, not by the bearing itself, so the bearing’s primary job is to support the rotating elements and minimize friction and wear.