GD&T - Part 7; Run-Out
A more specialist geometric tolerance, run-out tolerances combine a number of other geometric features including; co-axiality, roundness, cylindricality and even perpendicularity and flatness
into a specialist type of geometric tolerances specifically for rotary parts. Both circular and total run-out are applied to a component to control its circular or cylindrical features as the component is rotated through 360 degrees.
Circular Run-Out
Similar to other geometric tolerance group, run-out can be split into two categories, a 2D (circular run-out) and 3D (total run-out) variant.
Circular run-out can control the circularity of a feature relative to the components axis bounded by a 2D tolerance zone. This can be considered as measuring a combination of the component’s coaxiality and roundness at multiple cross sections along the applied length as the part rotates.
Total Run-Out
Total run-out can control the cylindricality of a feature relative to the components axis bounded by a 3D tolerance zone combing the applied control of coaxiality and cylindricality. Unlike circular run-out, total run-out is a measure of the full length of the applied surface as the part is rotated.
Controlling other Features with Run-Out
Both circular and total run-out can also be applied to a perpendicular surfaces relative to a datum axis.
Circular run-out applied to a perpendicular surface will only consider the surface perpendicularity as, like its measure of circular features, measurements are taken at multiple circular positions. The 2D tolerance zone created will be applied parallel to the datum axis direction.
Total run-out applied to a perpendicular surface will combine both the feature surface perpendicularity and flatness. Like its measure of cylindrical features, total run-out takes measurements across the full surface as the component is rotated, creating a 3D tolerance zone bounded by two surfaces.
