3/4-NGT Thread Gauges

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Precision Thread Gages - Standard & Special Thread Gages‎

Screw-Thread Standards for Federal Services, 1957. Handbook H28

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NGT (National Gas Taper) Threads

http://www.aimmeasurecare.com/thread-plug-gauges.html

http://www.indiamart.com/truthread-gauges-tools/thread-gauges.html#taper-thread-ring-gauges

"FED STD HANDBOOK H28 was a predecessor ANSI/ASME B1.1. The data in FED STD H28 is slowly, revision by revision, being removed and placed in ANSI/ASME B1 Standards. There seems to be no reason to maintain two separate yet identical standard systems. As of 2010 the Military has reduced its focus on keeping their standards current in favor of using nationalized standards. Much of the current FED STD H28 is more like an index which points you to ANSI/ASME publications.

In the case of the American National Standard Series (N-Series) screw thread the FED STD H28 was a little behind ANSI/ASME B1.1. After ANSI/ASME B1.1:1949 was published it took the Military until the 1957 edition of the Federal Standard Handbook H28 for the American National Standard Series screw thread to be removed and placed into FED STD H28 Nonmandatory Appendix 1. In next revision, which came nine years after ANSI/ASME B1.1:1960, the 1969 edition of the Federal Standard Handbook H28 removed the N-Series from the Nonmandatory Appendix. In Table 1.8a: Designations for UN, UNJ, N, NR thread series; the N-series was identified as being superseded by UN series. FED STD H28 has since been revised several more times.

SUPERSEDED
To be clear, the most concise definition of superseded is replaced with something better. In other words: Stop using that old N-Series. Get with the times. Start using the current Unified Inch Standard Series (UN-Series) screw threads."

http://www.ring-plug-thread-gages.com/ti-N-vs-UN.htm

Heck, I didn't even know about this thread standard. Learned something new today.

Lyn and SolarEagle,
Thank you so much for your helpful tips and information about screw threads.