Arc Master Radius Gauges should be used for REFERENCE only. They are NOT registered with any Industry Standards Organization.
IMPORTANT: What you should do when you first receive your radius gauge.
To ensure proper calibration of your radius gauge, we recommend that at first use, check the gauge on a sample arc and record the measurement. This sample arc should have a radius of 100” or larger. The larger the radius sample your gauge is checked on, the more accurate the check. Make a note of the radius measurement on the sample arc and refer to this sample arc for all your regular radius checks.