Accurately measuring threaded iron pipe???

[figs]

How does one accurately measure 1/2" threaded pipe? In other words, is there a rule of thumb that plumbers use to account for thread engagement in fittings?

Thanks

[hj]

There is no "accurate" measurement. We use an arbitrary value, and hope it works on the particular connection we are working on. Mine might be different from another plumber's. Usually, the joint is not so precise that an accurate measurement is necessary. If it is, figure long, and use a bigger wrench to tighten until it fits.

[figs]

For 1/2" threaded iron pipe, what value do you use to account for thread engagement in fittings?

Thanks

[jimbo]

"by the booK" the engagement for 1/2" IPS is 4 1/2 hand turns, for an engagement of 0.320 inches, followed by 3 wrench turns.

However, "the book" even says that field threads often do not comply totally with the spec, so there is some amount of "winging it".

[99k]

If you are a technical person and love data, there is a reference book called the Machinery Handbook that has all the specs for every imaginable thread

[hj]

for 1/2", I figure 1/2" back from the center of the fitting is where the thread will end up. In fact, I use the pipe size as that measurement all the way up to 1 1/2". For 2", I allow 1 3/4" from the center of the fitting.