Thread Check Inc. offers a complete line of NPTF Dryseal gages per ANSI/ASME B1.20.5 from 1/16 ‐ 3.0. Dryseal threads are based on the American pipe thread but differ in that they are designed to seal pressure tight joints without using sealing compounds. To accomplish this seal, the thread form is modified and more extensive gaging is required. The roots of both the internal and external threads are truncated more than the crests so as to make contact prior to flank contact. The roots of the threads crush the sharper crests of the mating threads to create a sealing action at the major and minor diameters which creates the dryseal pressure tight joint. L1 and L2 NPTF Ring gages and L1 and L3 NPTF plug gages provide an inspection of functional diameter excluding crest and root truncation. The coordinated use of both gages checks the taper of the product thread as well. Crest check plug and ring gages or 6 step gages are plain cylindrical tapered gages. The crest check ring gage checks the major diameter of the external thread. The crest check plug gage checks the minor diameter of the internal thread. Thread Check can also supply master gages to calibrate working gages to determine wear. Master gages should be purchased as a plug and ring gage set with a calibration record indicating the standoff from being flush to basic. Thread Check’s expert sales engineers can assist you with the selection and proper use of NPTF gages.
NPT Plug Gages per ANSI/ASME B1.20.1