Designer69
Senior Member
I see 1/2" or 1-1/2"NPT on drawings all the time. still don't know what it stands for. anyone know?
thanks
thanks
344.28 Reaming and Threading.
All cut ends shall be reamed or otherwise finished to remove rough edges. Where conduit is threaded in the field, a standard cutting die with a 1 in 16 taper (?-in. taper per foot) shall be used.
FPN: See ANSI/ASME B.1.20.1-1983, Standard for Pipe Threads, General Purpose (Inch).
While, as Rob pointed out, conduit threads are required to be taper threads, conduit couplings are straight threads.iWire,
Please remind me why there is a Taper vs. Non-Taper conduit threading.
Tapered threads are required by the NEC for RMC. I still occasionally see some NPSM or American Standard Straight Mechanical Pipe Thread dies on the job. Guys tell me that it allow the locknuts to go on easier. :roll:
344.28 Reaming and Threading.
All cut ends shall be reamed or otherwise finished to remove rough edges. Where conduit is threaded in the field, a standard cutting die with a 1 in 16 taper (?-in. taper per foot) shall be used.
FPN: See ANSI/ASME B.1.20.1-1983, Standard for Pipe Threads, General Purpose (Inch).
If non-tapered threads provide a more watertight seal, why does plumbing pipe use the same taper as we do? The only difference being that their couplings also use tapered threads.there are 2 types of threads ,the tapered threads and the non-tapered or parallel threads ,taperd thresds are what I have always met in the field and in equipment assembly.Non tapered threads usually provide a more water tight seal,but,are there any specific places or applications where the parallel thread is to be used?
Really? I thought rigid conduit and most fittings are straight threads? Isn't spinning on a lock nut the way to tell -- if it easily spins all along the thread, it is straight. If it gets tighter the further on the nut goes, eventually needing a wrench to turn it, then the threads are tapered?
I've had issues when buying conduit cut to length and then threaded with NPT threads -- the locknut that goes deepest may not easily go on as far as I would like. Or did the guy threading it just not thread enough of the pipe?
Our rigid couplings are what the plumbers call "thread protectors". They are a little longer than a [plumbing] pipe coupling.If non-tapered threads provide a more watertight seal, why does plumbing pipe use the same taper as we do? The only difference being that their couplings also use tapered threads.
I believe that's so the threads will engage fully before the pipes butt.Our rigid couplings are what the plumbers call "thread protectors". They are a little longer than a [plumbing] pipe coupling.