Pipe thread finish standards...

[quizzical1]

Hi All,

We had an instance where 1" NPT pipe threads were being cut with chatter (threading tool too small). Can anyone direct me to a source for NPT pipe thread minimum finish requirements? I checked Machinery Handbook, but to no avail.

Thanks...

 

[BillPSU]

If you are truly making NPT not NPTF threads the finish should not be a critical feature. The thread is not designed to seal pressure as the crest and the roots of the male and female threads allow leakage in the joint. Teflon tape or pipe dope must be used to assure a leak free joint. Workmanship is probably your biggest downfall. Some people will not use the part while others will not have a problem. The question I always ask myself, would I use this part if it was in my own house or business? If I wouldn't, I rework or scrap the part.