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Runout and TIR Basics
Guide · Updated October 27, 2026
TIR (total indicator reading) is the difference between the highest and lowest reading as a part turns. It's how shops measure runout on shafts, chucks, collets and spindles.
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Step by step
- Mount the indicator: Mount it rigidly on the machine or the plate.
- Touch the part: Bring it onto the surface with a little preload, square to it.
- Rotate: Turn the part one full revolution slowly.
- Read the TIR: TIR = max − min reading. It's double the offset for simple eccentricity.
- Check axially: Indicate the face to check axial runout (wobble).
Causes
- Dirty collets or tapers
- A worn chuck
- A bent part
- Uneven chuck jaw pressure
Related: indicator setup, V-blocks.
Quick shop check
TIR is the total indicator movement in one revolution. If the dial moves from −0.0004 in to +0.0006 in, TIR is 0.0010 in. On a round part, centerline offset is about half the TIR, about 0.0005 in here. Indicate close to the chuck and again 3 in out to see whether the part is tilted or offset.
Worked example: checking runout on a part in a chuck
A turned shaft is held in a three-jaw chuck. Mount a dial indicator rigidly on the carriage, bring the tip onto the diameter square to it with a little preload, and zero the dial. Turn the spindle slowly by hand one full revolution and note the highest and lowest readings. TIR is the high minus the low. For simple offset, the part's center is off by half the TIR. Repeat near the jaws and farther out; if runout grows with distance, the part is tilted, not just offset. Then indicate the face to check axial runout.
FAQ
What is TIR?
Total indicator reading: the full swing of the indicator over one revolution.
Is TIR the same as eccentricity?
For pure offset, TIR is twice the eccentricity.
Radial vs axial runout?
Radial is measured on the diameter. Axial is measured on the face.
How do I verify the indicator?
On gage blocks. Build any reference size free with the Gage Block Calculator at gageblockcalc.com.
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General shop information only — follow your gage manufacturer's instructions and your quality system.