Radius gauge calibration: how often, to which standards, and how
A radius gauge is a set of thin steel templates with precisely formed concave and convex edges used to check fillet and corner radii by the light-gap method. The template edges are the measurement reference, so calibration verifies each blade profile against a known radius, typically by projection on an optical comparator with radius chart overlays.
Also known as: radius gage, fillet gauge, fillet gage, radius gauge set
How often should a radius gauge be calibrated?
Inspect blades for nicks, burrs, and edge wear before use; re-verify any blade that has been dropped, filed against a part, or shows visible edge damage.
Where this number comes from
No standard or manufacturer sets a normative interval. Ape Software's published radius gage calibration procedure treats the gauge as an inherently stable device that does not require routine recalibration unless the user requests it; in practice quality systems assign a 12 to 60 month verification cycle using the general recalibration-interval methodology of ILAC-G24 / OIML D 10, adjusted for wear observed at each check.
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
- Frequency of contact use against hard or abrasive workpieces, which rounds and wears the template edge
- Whether the gauge is used for acceptance decisions on toleranced radii or only for rough shop reference
- Nicks and burrs from contact with machined edges, which create false light gaps
- Corrosion risk from handling thin unprotected steel blades without oiling
- As-found condition history from previous verifications, since undamaged blades are dimensionally stable
Standards relevant to radius gauge calibration
Provides the interval-setting methodology used for radius gauges, since no instrument-specific standard prescribes an interval; 2022 edition.
Standards are referenced by designation and title. For normative requirements, always work from the current edition of the standard itself.
How a radius gauge is calibrated
A typical radius 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.
- Clean each blade and inspect for nicks, burrs, corrosion, and edge wear; note as-found condition
- Select the appropriate calibrated radius chart overlay and mount it on an optical comparator with verified magnification
- Place each blade on the comparator worktable and align its profile with the best-fit radius circle on the chart
- Assess profile deviation for every concave and convex radius in the set and record as-found deviations
- Apply acceptance tolerances by size range (Ape Software procedure: plus or minus 0.002 inch for 0.016 to 0.125 inch, plus or minus 0.003 inch for 0.141 to 0.234 inch, plus or minus 0.004 inch for 0.500 inch and larger)
- Retire or replace blades outside tolerance, since radius gauge blades are not adjustable or reworkable
- Record as-left status for the set and issue a calibration certificate listing each blade checked
Reference equipment typically used
- Optical comparator (profile projector) with calibrated magnification
- Certified radius chart overlays for the comparator
- Vision measuring system or profile measurement software as an alternative to chart overlays
Good to know
No dedicated ISO or ASME product standard for fillet/radius gauges was found in this research session; calibration practice is grounded in published lab procedures (optical comparator with radius charts) and general interval methodology.
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Sources
- Ape Software, "Free Radius Gage Calibration Procedure" (published calibration procedure)
Interval claim: states the radius gauge is considered an inherently stable device that will not require recalibration unless specially requested; also supports the optical comparator method, comparator accuracy requirement, and the size-banded acceptance tolerances.
- ILAC-G24 / OIML D 10 Edition 2022, Guidelines for the determination of recalibration intervals of measuring equipment used in testing laboratories, ILAC and OIML
Interval basis: documents that no standard imposes a fixed interval and describes the methods (automatic adjustment, control chart, in-use time, in-service checking) used to set and adjust intervals for equipment like radius gauges.
- ACS Calibration, "Radius Gage Calibration" accredited service description
Confirms that ISO/IEC 17025 accredited laboratories offer radius gauge calibration as routine service, supporting the practice of periodic verification.
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.