Which statement best describes the potential effect of excessive shaft end runout on a rotating assembly?

• A. It improves alignment
• B. It reduces wear
• C. It can cause misalignment and wear if excessive
• D. It has no effect

Answer: (C)

Excessive shaft end runout creates a deviation of the shaft axis at the ends from a perfect, centered path. In a rotating assembly, that means the shaft won’t stay perfectly aligned with bearings, seals, and coupling faces as it turns. This misalignment leads to fluctuating loads and improper contact between parts, causing cyclic bending moments, vibrations, and increased friction. Bearings end up with uneven loading, seals and mating surfaces experience rubbing, and gear or coupling wear can accelerate. Heat buildup and accelerated wear shorten component life and raise the risk of failure. So, when runout is too large, misalignment and wear are the likely consequences.