When threading pipe, how does the schedule/strength change? 1

[ChEMatt]

A while back I was told threading a SCH40 pipe "makes it SCH20 at the threads". During a conversation today with a friend I was contemplating this rule of thumb and wondering if it's true? Where would I look up information on how much metal is removed at the threads, what is the resulting wall thickness, and if that then becomes the limiting strength point of any given pipe?

Thanks for your help!

-Matt

 

[csk62]

Asme B1.20.1 defines NPT thread dimensions. You can use equations from ASME B31.3 or similar to determine the reduced allowable working pressure rating of a given NPS pipe size.