In bearing geometry, the term used to describe the difference between rod bearing curvature and bore curvature is which?

• A. Runout
• B. Offset
• C. Clearance
• D. Spread

Answer: (D)

The idea being tested is how two curved mating surfaces relate when their curvatures don’t match. When the inner surface of a rod bearing has a different radius of curvature than the bore it sits in, the surfaces can’t share the same perfect circle. The term used to describe that difference in curvature is spread. It captures how much the bearing’s curvature “spreads” relative to the bore’s curvature, which in turn affects contact patterns and oil film behavior.

Runout describes a surface’s wobble around its axis, offset refers to a translational misalignment of centers, and clearance is the actual radial gap between the journal and bearing in operation. Spread specifically denotes the curvature mismatch between the two mating surfaces.