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How to Check a Dial Indicator with Gage Blocks
Guide · Updated October 27, 2026
Gage blocks are the simplest way to check a dial or digital indicator for accuracy over its travel. Zero it on one block, swap in known larger stacks, and the difference in reading should match the difference in size. Here are the test steps and stacks.
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Test steps for a 1 in travel indicator (81-piece set)
| Expected reading | Stack |
|---|---|
| 0.000 (zero) | 1.000 |
| 0.100 | 1.000 + 0.100 |
| 0.250 | 1.000 + 0.250 |
| 0.500 | 1.000 + 0.500 |
| 0.750 | 1.000 + 0.750 |
| 1.000 | 2.000 |
Test steps for a 25 mm travel indicator (88-piece set)
| Expected reading | Stack |
|---|---|
| 0 (zero) | 10 |
| 2 mm | 10 + 2 |
| 5 mm | 10 + 5 |
| 10 mm | 20 |
| 15 mm | 20 + 5 |
| 20 mm | 30 |
| 25 mm | 30 + 5 |
Step by step
- Set up rigidly: Mount the indicator on a heavy stand or height gage over a clean surface plate.
- Zero on a base block: Set the indicator on a 1.000 in (or 10 mm) block with a little preload and zero it.
- Swap in larger stacks: Replace the base with stacks at steps across the travel and note each reading.
- Repeat in both directions: Go up, then back down, to catch hysteresis and repeatability.
- Compare to spec: Compare each error with the indicator's stated accuracy and your shop's limit.
Tips
- Slide stacks in from the side instead of lifting the indicator, so the stand doesn't move.
- Clean each block and let it reach the plate's temperature. Hand heat can grow a stack enough to show on a 0.0001 in indicator. See temperature compensation.
- Use a base block from the same set so its grade error doesn't skew every reading. Background in grades explained.
- Checking other gauges too? See micrometers, calipers and height gages.
FAQ
How do you check a dial indicator with gage blocks?
Mount the indicator on a rigid stand over a surface plate, zero it on a base gage block, then swap in stacks of known larger sizes and compare each reading with the size difference.
What sizes should I use to check a 1 inch travel indicator?
With an 81-piece set, zero on 1.000 in, then check 1.100, 1.250, 1.500, 1.750 and 2.000 in (1.000 plus 0.100, 0.250, 0.500, 0.750 and a 1.000 or 2.000 block).
Can I check a test indicator the same way?
Yes for the reading over its short range, using small steps such as 0.0001 to 0.010 in made from the 0.1001 to 0.1009 and 0.101 to 0.109 series. Keep the stylus angle the same for every reading.
Why use a base block instead of the surface plate?
Zeroing on a block means every reading is a block-to-block difference, so the plate's flatness and dirt under the first reading matter less.
Is there a free gage block calculator for test sizes?
Yes. The Gage Block Calculator at gageblockcalc.com finds the fewest-block stack for any size in inch or metric sets. Free, no login.
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General shop information only — follow your gage manufacturer's instructions and your quality system.