GD&T Runout Symbol (Animations and Examples)

In circular runout a circular two-dimensional TZ is created around a datum axis. The arrow symbol for runout relates to the way it is measured, which should also help you understand how it works. A part being measured for runout must be held by its datum axis and rotated. The controlled cross section can then have a gauge pin held against it. As the part rotates around its datum axis the pin measures the total variation – or composite deviation – of the surface. If the composite deviation is small enough, then all parts of the surface fall into the prescribed circular TZ, which is a designated location from the axis. This is different from circularity in that runout also controls in relation to a datum axis. So a surface that is incredibly round, but is off center from the referenced axis will not meet the callout. Runout is also unique in that is can be used against any surface of the part as it rotates. This part can be held for rotation around it’s axis, and then surfaces that are parallel, angled, a