Depth gauge calibration: how often, to which standards, and how
A depth gauge measures the depth of holes, slots, and recesses from a reference base face, in caliper-type (vernier, dial, digital) and micrometer-screw versions with interchangeable rods. Accuracy depends on the flatness of the base reference face and the rod or blade length, so calibration against gauge block steps on a surface plate is essential.
Also known as: depth gage, depth micrometer, vernier depth gauge, digital depth gauge, dial depth gauge
How often should a depth gauge be calibrated?
Zero check on a surface plate or reference flat before use; immediate recalibration after a drop or when changing to an unverified measuring rod
Where this number comes from
No instrument standard sets a normative interval; JIS B 7518 and JIS B 7544 define accuracy requirements only. The 12-month starting point mirrors common quality system practice for the caliper and micrometer instrument family as stated by calibration providers (Houston Precision Instruments), adjusted by the user per ILAC-G24 / OIML D 10 risk methods.
Calibration intervals are a risk-based decision for the instrument owner, not a fixed rule: guidance documents such as ILAC-G24 and OIML D 10 describe how to set and adjust them from usage, criticality and calibration history. Treat the interval above as a starting point for your own quality system, not a compliance requirement.
What shortens or lengthens the interval
- Wear of the base reference face from sliding on rough castings or machined edges, which shifts the zero plane
- Use of interchangeable measuring rods on depth micrometers; each rod change risks seating error and each rod needs verification
- Usage intensity: daily production depth checks push intervals toward 3 to 6 months, occasional toolroom use supports longer intervals
- Criticality of depth tolerances such as counterbore and seal groove depths on safety-relevant parts
- Handling risk from drops onto the base or rods; recalibrate immediately after impact or if zero will not hold
Standards relevant to depth gauge calibration
Japanese Industrial Standard specifying maximum permissible errors for caliper-type depth gauges by measuring depth range, used as calibration acceptance criteria
Japanese Industrial Standard for micrometer-screw depth gauges (depth micrometers) up to 300 mm maximum measuring length, defining their accuracy requirements
Standards are referenced by designation and title. For normative requirements, always work from the current edition of the standard itself.
How a depth gauge is calibrated
A typical depth gauge calibration, in an accredited lab or in-house, follows this outline. The exact points, tolerances and paperwork come from the applicable standard and your own procedure.
- Inspect the base reference face, measuring rod or blade, and locking devices for wear and damage; clean all contact faces
- Allow the instrument, surface plate, and gauge blocks to stabilize at 20 C
- Verify the zero setting with the base seated on the surface plate and the rod or blade advanced to the plate surface, recording the as-found zero
- Build calibrated steps from gauge blocks on the surface plate and measure at minimum, mid-range, and full-range points; for depth micrometers include points at intermediate thimble positions to test the screw, not only full turns
- Repeat the range check for each interchangeable rod that is part of the instrument set
- Check repeatability by repeated measurement of the same gauge block step
- Compare errors against the JIS B 7518 / JIS B 7544 maximum permissible errors, the manufacturer specification, or a graduation-based tolerance; adjust the zero or repair as needed
- Record as-found and as-left data and issue a calibration certificate with uncertainty
Reference equipment typically used
- Granite surface plate (calibrated)
- Gauge block set (Grade 0 or better)
- Gauge block accessories for building depth steps
- Temperature-controlled environment at 20 C
Tracking depth gauge calibrations in a spreadsheet?
Gaugelog is calibration management software for quality managers who’ve outgrown Excel: instrument register, schedules, due-date alerts and certificates in one place. It launches in 2026. Until then, you can generate a clean calibration certificate PDF with our free tool, no account needed.
Sources
- Houston Precision Instruments, "How Often Should Calipers and Micrometers Be Calibrated?"
The 12-month common starting interval for the caliper and micrometer instrument family that depth gauges belong to, the 3 to 6 month shortening for heavy use, and the 18 to 24 month extension for lightly used tools with documented in-tolerance history
- APE Software, "Free Depth Micrometer Calibration Procedure" (Calibration Control help library)
The procedure outline: gauge block set and surface plate as standards, zero verification on the surface plate, test points at zero, midway, and full length including intermediate thimble positions, and graduation-based acceptance tolerances
- JIS B 7518, Vernier, dial and digital depth gauges, Japanese Standards Association
Standard designation and title, and the depth-range-dependent maximum permissible errors used as acceptance criteria for caliper-type depth gauges
- JIS B 7544:1994, Depth micrometers, Japanese Standards Association
Standard designation and title for micrometer-screw depth gauges (depth micrometers) up to 300 mm maximum measuring length
Cite this data
Gaugelog Calibration Interval Reference, v1.0 (July 2026). 68 instrument types, 236 verified sources. Licensed CC BY 4.0.
Download as CSV or JSON. Intervals are typical starting points, not compliance requirements; every row cites its sources.
The interval on this page is one row of the dataset. Browse all 68 types on the calibration interval reference.