Threading help

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Is there a formula for figuring out the major diameter of a custom thread? For example: I have a tube that is 1.384 inside diameter and I internal thread it 32 TPI. How do I determine what size to turn the OD of the male part prior to threading it?


You must know the thread form so you should be able to plug the numbers into the standard calculations.
Machinery's Handbook is a handy thing to have laying around ;-)
I tried the TM site calculator but its doesnt work out or im doing wrong. I guess if I add the thread depth to the OD it should fit?
If you are doing 32 tpi, the thread depth is 0.021 inch. I would start with stock that is 0.042 inch larger than your 1.384 ID.
If you haven't already, I would cut the internal thread first and then start with 0.042 oversize and use your tube to check the fit as you get close to the 0.021 thread depth.
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