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.