The thread ring gauge is used to measure the accuracy of external thread dimensions, with one piece at the through end and one piece at the end. The stop ring gauge has grooves on the outer cylindrical surface. When the size is above 100 millimeters, the threaded ring gauge is of the double shank threaded ring gauge type. The specifications are divided into three types: coarse teeth, fine teeth, and pipe threads. Thread ring gauges with a pitch of 0.35 millimeters or less and higher than level 2 precision, as well as thread ring gauges with a pitch of 0.8 millimeters or less and level 3 precision, do not have a stop end. Thread ring gauges can be divided into metric thread ring gauges, imperial thread ring gauges, American thread ring gauges, and trapezoidal thread ring gauges. All specifications are made according to the specifications, and non-standard products can also be customized according to customer requirements.

There are two calibration methods for taper shank thread gauges and thread ring gauges. One mainly uses a length gauge, a length measuring machine, and its accessories (such as internal measuring hooks, measuring balls, calibration rings, etc.) for measurement. The measurement process is relatively complicated, the calculation is complex, the efficiency is low, and the requirements for operators are also high. In order to improve the verification and calibration efficiency of thread ring gauges and reduce their complexity, metrological verification departments (such as provincial and national defense metrology) often use thread calibration plug gauges to verify and calibrate working thread ring gauges. It is well known that the detection of external threads is much simpler than that of internal threads, which is also the main reason for using calibration thread plug gauges.