Gauging 1.5 npt / 1.5 line pipe / 1.9 sharp vee

[pppmike3p]

All three types of threads appear to be the same. I'm thread milling a 1.9 sharp vee thread and trying to gauge it with a 1.5 npt plug guage. Not sure if this is correct but it does seem close. The major dia. of all three threads are 1.9 and all 3 are .75 TPF and 11.5 TPI and dia at face are the same and thread bore dia match only difference is thread length.

I have seen 1.5 line pipe and 1.5 npt plug guages and they do appear different, 1.5 npt plug guages have a milled flat on them. 1.5 line pipe plug guages have 3 lines on them.

I would greatly appreciate it if someone could tell me the differences if any and if i could use the gauges on the different threads!

Thanks

[ctate2000]

Call the gage maker and ask. We make UNFJ threads all the time and the plug gage is same as UNF. Gage maker can tell you.

[eddiewdi]

Hope I am not too late in replying to this inquiry. All three threads are not the same.
The 1.5 NPT and 1.5 LP are interchangeable. The "1.9 sharp Vee" per API 6A 19th page 378 is actually a 1 1/2-11 1/2 tpi sharp thread nonupset tubing. THIS THREAD IS NOT INTERCHANGEABLE WITH 1.5 NPT OR 1.5 LP. The sharp vee thread is specified in API Bul 5A second edition 1944