Calibrating adjustable thread ring gages can get a bit sticky on occasion due to customer assumptions versus the requirements of ISO 17025. It takes a lot of diplomacy to sort out situations where this type of gage is involved due to the number of phantom setting plugs drifting around inspection departments all over the country.
Since we provide an accredited calibration service for such gages, customers assume that we can do so all the time. This is not a problem where the threads involved are standards as are the setting plugs used to check them. When this is not the case, most customers will understand that we cannot stock special setting plugs and provide one they may have on hand for their special rings.