NPTF Male Fitting vs. NPT tap Adapter

[GenJT]

Hi evryone,
I have a 1-11.5 NPTF fitting part made from oversee and it won't mate with the 1" NPT part. I have done the search for info of the difference between the two & why that they do not mate, but I have yet found nothing.
If anyone has the info or tell me the reason why 1" NPT does not accept the 1-11.5 NPTF fitting.
Thanks,
Gen

 

[Cockroach]

Your thread pitch may be off.

I use "FNPT" to designate box or female thread specification form "MNPT" or pin, i.e. male threads. But this is oilfield jargon, box & pin nomeclature that does not necessary translate to other industries.

Good luck with it. An NPT is an NPT, so you have something special like a machining error?

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[Timelord]

GenJT,

NPTF is the designation for Dry Seal (SAE standard J476) pipe threads. They have the same pitch and taper as NPT threads, but the thread form is modified to seal better. A NPTF should mate with a regular NPT, and 11-1/2 is the correct pitch for 1" pipe. I would have to agree with Cockroach, it may be a machining error or the female end may not be tapped deep enough. For more info, see the link:

http://www.webster-inst.com/techinfo/pipeconn/pipefr/pipeconn.htm

Timelord

 

[GenJT]

Thanks Cockroach & Timelord.
I did believe they should work but apparently they did not. I did use 1" NPT male and it works fine with the 1" NPT female. The next thing I will do is the verify the NPTF male thread and how it machined as you have mentioned.

 

[Cockroach]

Yeah, the NPTF is probably tapped. I agree with TimeLord though, they should fit, all things being equal.

Good luck with it!

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada