Gauges for taper pipe threads are used to inspect taper pipe threads and parallel pipe internal threads that fit taper threads. A taper thread plug gauge and a taper thread ring gauge form a pair of gauges for taper pipe threads. To inspect the manufacturing tolerance for an internal taper thread or external taper thread, the notch in the large end of a taper thread plug gauge or the small end of a taper thread ring gauge is referred to. When a taper thread plug or ring gauge is screwed up into or on an internal or external taper thread by hand, the pipe or pipe fitting passes the inspection if its end is within the range defined by the notch. The JIS standard for taper pipe threads was revised in 1982. Its main text sets out the content of ISO 7/1, using thread symbols “R. Rc and “Rp.” Symbols “PT” and “PS” used in the previous JIS edition are specified in the Appendix to the standard. To inspect pipe threads specified in the revised JIS, gauges that bear the new thread symbols should be used.
OSG
Taper Pipe Thread Gauge (TG)
Used to inspect taper pipe threads (R・PT). There is a notch on the side, and if the end of the screw is within the scope of the notch, it is a pass. This indicates the point of standard dimensions in the ANSI (NPT/NPTF), and there are 3-4 stage notches are installed.
