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What is the proper thread engagement for an NPT pipe?

Question asked by Steve Calvert on Aug 30, 2018
Latest reply on Aug 31, 2018 by David Matula

I think I already know the answer but I wanted to ask anyway.  I have several sizes of aluminum conduit that we make in house for our dispensers and one end is always threaded NPT so it can be threaded into another component.


Some designers and Engineers just justimate a close number and use that but I wanted to set my pipes to have a plane that's offset from the end of the pipe that represents a standard length.


So, for this example I'll use a 1/2" NPT threaded into a component (a valve).  What is the actual offset should I use from face to face?


I was always taught to use the Machinery's Handbook and go to the American Pipe Threads section and add together the "Handtight Engagement L1" and the "Wrench Makeup L3" to get the offset distance.  I've been using this for decades and I know I'm splitting hairs here but just wanted to establish a standard.





Steve C