How to Measure 1/4-18 NPS OD Thread?

[munruh]

I took this job on---a fitting that has 1/4 NPT threads, a groove and then the threads go to 1/4 straight pipe threads. Now I am writing a program and thinking how I am going to check these threads. How do you check straight pipe threads? thread wires? I don't have a fitting to check them and neither does my threadwire software have any MOW for straight pipe threads. Thanks

 

[jkruger]

The data you need is in Machinery's Handbook. Thread wires are the only way I have ever done it. I would not trust using a fitting, the fitting the customer has might be a different size so you need to make yours to the specs.

 

[munruh]

The data you need is in Machinery's Handbook. Thread wires are the only way I have ever done it. I would not trust using a fitting, the fitting the customer has might be a different size so you need to make yours to the specs.

Okay, will there be an actual MOW chart for straight pipe threads or will I need to do the math?

 

[rbrandes]

Look under "gas pipe threads." I don't think it is in the threads section of MachHB, but somewhere else. The threaded tubes used for lamps are such a thread, a hold over from the days of gas lighting.
Regards, Ray
PS:Look under Gas Fixture Dies - on page 1466 17th edition.

 

[mrainey]

ThreadPal does MOW calculations for NPSM and NPSL threads. The demo version will do 1/4-18.


ThreadPal

 

[Hertz]

Correct me if I'm wrong but NPS threads are still 60 degrees? I would just use the .032 wire size. I don't really see an issue here. Of course I may be missing something? Diameter of a 1/4 NPS is about .527 so add .0118 to get your MOW with the .032 wires.