What term describes the variations of a surface as it rotates around a datum axis?

Runout refers to the variations that occur on a surface as it rotates around a datum axis. It assesses how much a part deviates from its intended rotational path, determining the extent to which a surface can wobble or move off its intended position during rotation. This measurement is critical in ensuring the performance of rotating components, as excessive runout can lead to vibrations, increased wear, or failure in machinery.

The concept of runout includes both circular runout, which looks at the variation in distance from a rotational axis at different points along the surface, and total runout, which evaluates the entire surface’s movement as it spins. Understanding runout is essential in various engineering fields, particularly in machining and assembly processes, where precise alignment and surface integrity are crucial for optimal performance.

The other terms relate to different aspects of measuring and defining surface characteristics. Flatness refers to the evenness of a surface in all directions, without regard to its orientation. Tolerancing defines acceptable limits of variation in dimensions or features of a part. True Position involves the actual location of a feature relative to its intended location but does not specifically address the variations caused by rotation around an axis. Hence, when discussing the variations of a surface during rotation, runout is the