All UN, UNJ, M, and MJ thread form gages shall be calibrated using the commonly accepted metrology techniques described in this standard using properly maintained standard metrology equipment. The practices described in this standard are minimum calibration requirements. If alternative calibration methods or equipment are used, it is the user’s responsibility to verify that the measurements obtained are accurate and correlate with measurements generated when employing the methods and equipment described in this standard. The calibration methods contained in ASME B1.2 or FED-STD-H28 are acceptable, but their use does not absolve the user from verifying their measurement capability.

This standard describes two different categories of calibration, Initial Calibration and Subsequent Calibration.

Initial Calibration applies to all new thread gages. All thread gages either used to verify product conformance or to calibrate gages shall be calibrated for all characteristics specified in this document.

Subsequent Calibration is the evaluation performed on a periodic basis as set by the user following the Initial Calibration. There are fewer required measurements in the Subsequent Calibration than in the Initial Calibration because it does not take as many measurements to detect gage wear or damage as it does to determine a gage’s initial acceptability to the standard requirements. After the adoption of this standard, gage users shall have an Initial Calibration certificate on file for a gage prior to the performance of a Subsequent Calibration on that gage.

Refer to ASME B1 Technical Report “Measurement Uncertainty for 60 degree Screw Thread Gage Element Measurement Inch and Metric” to resolve any gage acceptability disputes.