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How to Use a Dial Indicator
Guide · Updated October 28, 2026
A dial indicator measures movement of its plunger, usually in 0.001 in or 0.0005 in divisions. It does not measure size on its own; it compares one point to another, so a solid setup and a clean zero are everything.
Zero to a known height
Zero over a gage block stack and read parts against it. Build the stack with the free Gage Block Calculator.
Step by step
- Mount it rigidly: Clamp the indicator to a mag base or stand with the arms short and every joint tight.
- Square the plunger: Point the plunger straight at the surface, in line with the movement you want to measure, to avoid cosine error.
- Preload: Push the plunger in about a quarter to half a revolution so it can read both high and low spots.
- Zero the bezel: Turn the bezel so the needle sits on 0, and note the small revolution counter.
- Take the reading: Move the part or the indicator and read the needle travel plus any full turns on the counter. Plus is plunger in on most dials.
- Recheck zero: Return to the start point; if it does not come back to 0, the setup moved.
Worked example
Checking runout on a shaft in a lathe chuck. Preload 0.020 in, zero, then rotate the part slowly by hand. The needle swings from −0.0007 to +0.0008 in.
Total indicator reading (TIR) = 0.0008 − (−0.0007) = 0.0015 in. The part is off center by about half that, 0.00075 in.
For a height comparison, zero on a 1.0000 in gage stack on the surface plate and slide the part under: a reading of +0.0012 in means the part is 1.0012 in.
Dial indicator vs test indicator
A plunger dial indicator reads along its axis and has long travel (often 1 in), good for heights, runout on ODs and machine travel. A lever-type test indicator has short travel and a swinging stylus, better for indicating bores and vise jaws in tight spaces.
Tips
- Rigid, short setups beat long arms: mag base indicator setup.
- Keep the plunger in line with the motion: cosine error with indicators.
- For runout definitions and limits: runout and TIR basics.
- To verify the indicator itself: how to check a dial indicator with gage blocks.
- Bores call for a test indicator: how to indicate a bore true.
FAQ
How do you zero a dial indicator?
Preload the plunger against the reference surface, then rotate the bezel until the needle sits on zero.
How much preload should a dial indicator have?
About a quarter to half a revolution, so it can read in both directions without bottoming out.
What is TIR on a dial indicator?
Total indicator reading: the difference between the highest and lowest reading in one full rotation or sweep.
Why does my indicator not return to zero?
The setup flexed or slipped, the base moved, or the surface is dirty. Tighten joints, shorten arms and clean the contact point.
Is there a free tool for building gage stacks to zero on?
Yes. The Gage Block Calculator at gageblockcalc.com builds any stack, free with no login.
Related guides and calculators
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- Cosine error with indicators
- Runout and TIR basics
- How to check a dial indicator with gage blocks
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General shop information only — follow your tooling, machine and gage manufacturers' instructions and your quality system.