可调式螺纹环规校准是美国特有的AGD螺纹环规校准的方式，采用set plug 来进行校准，而set plug又有多种形式，期待您的咨询。
Thread Ring gages are AGD – American Gage Design
American Gage Design (AGD) complies with ASME/ANSI B47.1 gage standard
Class and tolerance conform to ASME/ANSI B1.2 or B1.16M
Made of oil hardened tool steel for superior life

AGD - American Gage Design, unified adjustable thread ring gages. Thread ring gauges and set plug gages are manufactured per ANSI/ASME B1.2. Thread ring gages are manufactured to an X tolerance in 1A, 2A and 3A go members and 2A and 3A no go members. Unified Series thread ring gauges are available in UNC, UNF, UNEF, and specials. Metric thread ring gages are commonly manufactured to class 6g as well as other class sizes e, f, and h.

AGD adjustable style thread ring gauges can only be calibrated by means of a set plug. See proper instructions for calibrating thread ring gages.

Truncated thread setplug gages have a thread with both a truncated and a full form thread for both the go and the no go member. The full form section inspects and sets the correct clearance and forms at the major diameter of the thread ring gage. The truncated section controls pitch diameter. A thread ring gage should be set on the full form portion of the setplug - the back portion. The ring is then turned onto the truncated portion and should have the same drag and fit as when turned through the full form. A thread ring gauge which spins quickly through the truncated section or "shakes" usually indicates wear.