Runout
Glossary · Tolerance & Measurement
At a glance
- Category /
- Tolerance & Measurement
- Also called /
- run out, TIR, total indicator reading
- Related /
- 3 terms
- Source /
- Written in the shop
Runout is the total movement shown on an indicator when a part is rotated one full turn, measuring how far a surface wobbles relative to its axis.
Also called: run out · TIR · total indicator reading
In practice
You clamp the part, put an indicator on the surface, and rotate it. The difference between the highest and lowest reading is the runout — often written TIR, for total indicator reading. It captures roundness and centering at the same time.
Why it matters
Runout is what makes a rotating assembly vibrate. On a shaft carrying a seal or bearing, excess runout destroys the seal long before the shaft itself wears out.
More in Tolerance & Measurement
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