Apr 26, 2005 · The only difference between the internal UNJ thread and the standard UN threaded is that the UNJ thread has a larger minor diameter. The thread work plug gage does not check the minor diameter of the thread, thus when checking the threads, standard UN style Work Plug Gages are used.

Thread Check provides information on UNJ and UN threaded product compatibility. Contact us for additional details on UNJ thread and gage requirements.

UNJ, UNJC, UNJF and UNJEF threads are almost identical to UN, UNC, UNF, and UNEF threads except that the external J thread has a much larger root radius than the standard UN threads and inspection must be performed on this element. The Special UNJ threads are designated by the nomenclature UNJS.

Jul 31, 2014 · The US Government through FED-STD-H28/2B is directing manufacturers to use the current ANSI/ASME B1.1 UN-series screw threads and classes-of-fit instead of the OBSOLETE N-series which is specified on many old US Government part drawings.

Feb 8, 2025 · Defines thread specifications, including UNC (Unified National Coarse) and UN8 (8 threads per inch), commonly used for stud bolts. Download the ASME B1.1 pdf standard here. This Standard specifies the thread form, series, class, allowance, tolerance, and designation for unified screw threads.

Jun 16, 2010 · 1. The only difference between UNJ 'GO' & UN 'GO' is that UNJ 'GO' ring gauge has enlarged minor dia to clear the large root radius. If UN 'GO' is used to measure UNJ, the gauge will reject the component. But UN 'NOGO' is identical to UNJ 'NOGO'. 2. The UN & UNJ thread plug gages are interchangeable.

The UNJ thread standard (ASME B1.15) defines a system of threads for highly stressed applications requiring high fatigue strength. It was derived from a military specification (MIL-S-8879) originally published in December 1965.

ASME B1.1 is a Standard that specifies the thread form, series, class, allowance, tolerance, and designation for unified screw threads.

UNJ bolts are like UNR, but the curve of the bolt thread root is even more gentle which requires the thread root to be shallower. In fact, the thread root is so shallow that the bolt thread cannot mate with a UN nut, so there is a UNJ nut specification as well.

An internal UNJ thread will assemble to a standard UN external thread but the reverse is not the same due to the interference at the minor diameter. The UNJ external threads have a larger root radius than a standard thread pitch.