How to Inspect Runout Tolerance – GD&T
When inspecting circular runout, the feature, first, must fall within the specified size limits. It must not exceed the boundary of perfect form at maximum material condition. The datum feature is then mounted in a chuck or a collet. With a dial indicator contacting the surface to be inspected, the part is rotated 360◦ about its simulated datum axis. Several measuring positions are inspected. If the full indicator movement (FIM) does not exceed the specified runout tolerance, the feature is acceptable. Runout tolerance may be larger than the size tolerance. If the runout tolerance is larger than the size tolerance and no other geometric tolerance is applied, the size tolerance controls the form. If the size tolerance is larger than the runout tolerance, circular runout refines circularity as well as controls coaxiality. The same preliminary checks required for circular runout are also required for total runout. Just as when inspecting circular runout, a dial indicator contacts the surface to be inspected, but the dial indicator is moved along the full length of the feature’s profile as the part is rotated 360◦ about its simulated datum axis. If the FIM does not exceed the specified runout tolerance, the feature is acceptable.