↗ Circular runout
Circular runout · Oscilación · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
As the part rotates on datum A, the radial variation in the measured section must not exceed 0.03 mm over one full turn. It combines eccentricity, ovality and misalignment in a single reading.
What controls
Controls, at a specific cross section, the total variation (combining form and location) of a circular feature or a face as it rotates 360° about the datum axis. Unlike circularity (which requires no datum), circular runout does depend on how the part is held on the reference axis: eccentricity, ovality and misalignment are mixed into a single reading, without distinguishing which of the three causes the error.
How to verify
Mount the part between centers (or on an arbor/chuck that faithfully simulates the datum) and set a fixed dial indicator, perpendicular to the surface, at the section being checked. Rotate the part one full turn: the difference between the maximum and minimum reading is the circular runout at that section. Repeat at several sections if the drawing requires it — each section is evaluated independently, not cumulatively.
tolerance zone
At each section, the indicator reading over one full revolution may not exceed the stated value.
Datums and notes
Requires an axis datum (normally A).
Workshop guideline values
- General
- 0.03–0.08 mm on bearing surfaces or flanks in general machining.
- Accuracy
- 0.01–0.03 mm on bearing seats or close-fit shafts.
- High precision
- 0.003–0.008 mm on precision shafts or dynamic sealing surfaces.
Guidance only: the drawing's value always wins.
Common mistakes when interpreting it
- Blaming high runout on a machining error without first checking the TIR of the workholding: in most cases the problem is eccentricity of the chuck, collet or arbor, not the part.
- Measuring with the part mounted differently from how the datum is defined on the drawing: runout depends directly on how the part is held during measurement, not just on its geometry.
How to get it in the workshop / if it comes out of tolerance
Faster to measure than total runout: a single measuring plane per pass. Typical on gear flanks and cylindrical bearing surfaces.
Runout almost always points to a workholding problem, not the part itself: check the TIR of the chuck/collet/arbor before starting, and mark the angular position if you are going to unload and reload the part between operations. If runout increases with spindle speed, suspect imbalance (off-center part or worn chuck), not a machining error.
Related symbols
Other symbols in Runout
See the full symbol libraryRelated tools
ISO fits
Calculates indicative ISO 286 tolerances for shaft and hole, H7/g6, H7/h6, H7/k6 and H7/p6 fits with clearance, transition and interference graph.
Inspection Plans
Upload a plan, extract dimensions and GD&T with AI and export your inspection guideline in PDF or CSV.
Shop trigonometry
Workshop trigonometry: right triangle, C chamfer, Z countersink, sine bar, taper and polar→X/Y for CNC operators.