Pipe thread callouts

[KimBellingrath]

The proper callout on a drawing for NPT is:

1/2 NPT, or 3/8 NPT but when you get to an inch is it:

1 INCH NPT or 1" NPT?

Please don't guess - everyone here is guessing. Does anyone have the definitive answer?
Thanks,
Kim

 

[ewh]

IAW Machinery's Handbook, niether are correct. You call out nominal size (1), the number of threads per inch (11 1/2) and the symbols for the thread series and form (NPT)
Therefore, it is "1 - 11 1/2 NPT".

Eric

 

[unclesyd]

The normal call out for pipe fittings is 1" NPT without the threads/inch.
Even though 1"-11 1/2 NPT is correct this is normally reserved for use when purchasing taps and dies and such.

If you do use the thread call out you will need to have another descriptor, such a elbow, tee, etc.