Engineering · GD&T
Total runout.
The most comprehensive runout tolerance. As the part rotates about a datum axis and the indicator traverses the full toleranced surface (axially along a diameter; radially across a face perpendicular to the axis), FIM must stay within the tolerance value. Captures at-section roundness, axial straightness, taper, and coaxiality in one number.
01 · Definition
Indicator at every section, simultaneously.
Total runout is the volumetric counterpart to circular runout. The part rotates about its datum axis, and the indicator (or CMM probe) traverses the full toleranced surface — axially along a diameter, or radially across a face perpendicular to the axis. The total indicator reading across the whole inspection — not just one section — must stay within the tolerance value.
Total runout simultaneously controls four things: at-section roundness, axial straightness, taper, and coaxiality. It’s effectively cylindricity referenced to a datum axis — the most comprehensive control for rotating cylindrical surfaces.
02 · FCF and example
0.003 total runout on a rotor shaft.
A turbine-rotor shaft with ⌰ 0.003 A means as the shaft rotates about its center datum axis and the indicator traverses the full length of the toleranced surface, the highest minus lowest reading must be ≤0.003″. Round at every section, straight along the axis, no taper, no axial wobble — all inside one number.
Inspection: between centers with a precision dial indicator that traverses axially as the part rotates, or CMM scanning probe with axis-of-rotation fixturing.
Production strategy: rough and finish in one chucking, with the eventual datum axis as the turning center. Re-fixturing between rough and finish destroys total runout — coaxiality requires single-setup execution.
03 · Common applications
Where total runout matters.
- Rotating shafts: turbine rotors, motor shafts, gearbox input shafts — any rotating element where dynamic balance matters
- Sealing surfaces: dynamic seal lands need total runout to maintain seal contact across full rotation
- Bearing seats: for shaft bearings to run true, the seat needs total runout control to the rotating axis
- Aerospace shaft work: landing-gear actuator shafts, helicopter rotor mast components
- Defense fastener turning: precision pins where coaxiality matters across the full L:D — Swiss-type production. See Swiss vs. CNC lathe.
Keep exploring
Related tools & references
Full feature-control-frame symbol reference.
The single-cross-section version of total runout.
Form control bounded within a total-runout reading.
Check how runout accumulates across a shaft.
How tight a total-runout callout drives cost.
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