Total Runout — Runout Tolerance

Limits composite variation over the entire surface in one measurement pass.

Definition

Total runout limits how much an entire surface may vary relative to a datum axis, evaluated simultaneously as the part rotates and the indicator traverses along the surface. It is the whole-surface member of the runout family: where circular runout reads one section at a time, total runout's single pass covers every section at once, so it additionally controls the surface's straightness and taper along the length — variations that circular runout, checking section by section, never sees. Like its sibling, it is composite (roundness, coaxiality, straightness and taper all in one number), it requires a datum reference because rotation about the datum axis is the method, and it never takes a material-condition modifier because it controls a surface.

The zone, and the cylindricity parallel

The total runout zone is the space between two coaxial cylinders of radial separation t, centered on the datum axis, and the entire actual surface must fit between them in the single combined rotation-and-traverse evaluation. On a face perpendicular to the axis, the zone is instead two parallel planes t apart. The structure repeats a relationship this library has already seen: circular runout is to total runout what circularity is to cylindricity — the per-section control and the whole-surface control of the same family, with the whole-surface member additionally bounding the along-the-length errors. The difference is what the zone is anchored to: cylindricity's envelopes are self-referencing (no datum), while total runout's are centered on the datum axis — cylindricity controls form only, total runout controls form and location together, which is what makes it the stronger and more functional callout on rotating parts.

Reading a feature control frame

↻ 0.05 A–B reads as: a total runout tolerance of 0.05, evaluated over the entire controlled surface as the part rotates about the common datum axis A–B. The double-arrow symbol is the only difference from circular runout's frame — same no-modifier rule (a surface, not a feature of size), same mandatory datum reference — but the two arrows change the meaning of the tolerance: not one section's FIM, but the whole surface's excursion in one pass. A drawing that needs both controls on the same surface calls them out in stacked frames, circular above total, tightening the per-section requirement inside the whole-surface one.

Measurement

Bench center + dial indicator with traverse — mount the part on the datum axis, zero the indicator, then rotate the part continuously while sweeping the indicator along the full length of the controlled surface; the total indicator movement over the entire pass must not exceed t. Same bench setup as circular runout, one added motion.

CMM surface scan — probe the surface along helical or raster paths and evaluate the tightest pair of coaxial cylinders about the datum axis that contains the points. Used where the part cannot be rotated, or where the along-the-length components (taper, bow) must be separated for process work.

When to use it

• Long rotating surfaces where taper or bow would matter as much as local roundness — lead screws, spindle surfaces, long shaft seats
• Faces that must run square to the datum axis (total runout on a face uses a planar zone) — flange faces, bearing shoulders
• Surfaces needing both a per-section and a whole-surface requirement — the stacked circular-over-total callout
• Any location-plus-form requirement on a rotating surface where cylindricity alone would leave the surface free to sit anywhere relative to the datum