Tolerance on the outer diameter and end of threaded pipe
Tolerance on the outer diameter and end of threaded pipe
(OP)
Hi All
I have a part that should be connected to a water pipe. I see a tolerance of -0.2 to -0.3 as you can see in the image on the outer diameter of the exit pipe of my part that will be connected to the water pipe. I have just put the dimensions that are relevant to my question. I have seen this tolerance on an existing design. I don't know two things : what is there the small taper before the thread starts? and why should we have such a tolerance?
I have a part that should be connected to a water pipe. I see a tolerance of -0.2 to -0.3 as you can see in the image on the outer diameter of the exit pipe of my part that will be connected to the water pipe. I have just put the dimensions that are relevant to my question. I have seen this tolerance on an existing design. I don't know two things : what is there the small taper before the thread starts? and why should we have such a tolerance?





RE: Tolerance on the outer diameter and end of threaded pipe
Go here to see what it should look like:
https://www.google.com/search?q=image+of+taper+pip...:
Straight threads will not seal.
Sometimes its possible to do all the right things and still get bad results
RE: Tolerance on the outer diameter and end of threaded pipe
It appears to be a straight thread so needs a separate sealing surface.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Tolerance on the outer diameter and end of threaded pipe
What did you copy that termination from?
Maybe documentation for that product will answer your questions.
Mike Halloran
Pembroke Pines, FL, USA
RE: Tolerance on the outer diameter and end of threaded pipe
Thank you very much. you are right, it should have a taper ! only thing that when I opened the relating page , it was for stair banister railings. But I think I am sure what should I find.
@Mike Halloran : Usually if a young engineering team puts hands on old drawings, doesn't tend to do the same engineering but copies the same dimensions and notes, without noting what is happening and not being sure what they can remove. I wanted to do some more investigation. Such documentaion doesn't exist for the part connection( other normatives on other characteristics do though). So for the connection, I think I have to follow pipe fitting standards, yet I don't understand that strange tolerance
RE: Tolerance on the outer diameter and end of threaded pipe
It's also common to find a separate bevel on the same end, applied after threading to remove the sharp projecting half-thread shown in your drawing. That fragile half-thread facilitates cross-threading and leaks.
I suggest getting on the phone Real Soon Now and talking to any surviving old timers you can find; maybe someone will remember why the joint looks the way it does.
In the meantime, we here might be able to make better guesses, given photographs and/or fully dimensioned drawings of the parts.
Mike Halloran
Pembroke Pines, FL, USA
RE: Tolerance on the outer diameter and end of threaded pipe
But your help was quite useful for me. That I did not know that half threads might create problems.