What is the meaning of 'runout' in engineering terms?

The term 'runout' in engineering relates to both surface variations and geometric tolerances, making the correct answer a combination of both concepts.

Runout specifically describes the deviation of a surface or feature when it is rotated around an axis. It is crucial in assessing how well a component will perform in practical applications, particularly in rotational parts such as wheels or shafts where the accurate alignment of surfaces is essential to maintain functionality and minimize wear.

Measuring runout helps engineers ensure that the manufactured parts meet specific tolerances, which prevents issues such as vibration, noise, or premature failure in mechanical systems. Thus, it serves as a key indicator of the quality and precision of machined surfaces, effectively bridging surface variations and the broader context of geometric tolerances. By recognizing that runout reflects both a measure of surface variation and a specific type of geometric tolerance, one can better appreciate its significance in engineering practices.