Rigid Threader

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National Pipe Taper, same as plumbers. Sorry, but you're mixed up. Straight Mechanical threads would actually be a code violation.
 
This is a common misconception. I asked the steamfitter the other day if I could use his threading machine to make a few threads on some 3/4" RMC, he told me sure but that the threads wouldn't be any good because they're not "non-tapered electrician's threads". Even the other trades have this one wrong. :rolleyes:
 
Look at RMC factory 90's, or even the threads on the end of pipe, and it's clear they're tapered. EMT fittings, and the like, aren't tapered, which is one reason why some people remain dubious about the grounding capabilities of straight thread fittings screwed into couplings and hubs.
 
infinity said:
This is a common misconception. I asked the steamfitter the other day if I could use his threading machine to make a few threads on some 3/4" RMC, he told me sure but that the threads wouldn't be any good because they're not "non-tapered electrician's threads". Even the other trades have this one wrong. :rolleyes:
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I wonder if it comes from the "stuff" that ceiling luminaires are hung on? That is, I believe, straight threaded pipe of some standard dimension.
 
I'd have to think that the die teeth would be right expensive for straight thread. Supply and demand...

Straight threads run real easy, though. I have one of those three sided bolt dies, and they run like butter.
 
480sparky said:
They work, but they're not legal.
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Ok, Now im CONFUSED!! you say that using the 'plumbers threads' are NOT legal, but mdshunk (marc) says its the same post 2

mdshunk said:
National Pipe Taper, same as plumbers. Sorry, but you're mixed up. Straight Mechanical threads would actually be a code violation.
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Also infinity says it too post 7


infinity said:
This is a common misconception. I asked the steamfitter the other day if I could use his threading machine to make a few threads on some 3/4" RMC, he told me sure but that the threads wouldn't be any good because they're not "non-tapered electrician's threads". Even the other trades have this one wrong.
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Real life experience:

Nasty, cold mid winter job at a jail. Threaded rigid coming out of wall and very hard to reach. We were out of couplings so I asked our nit wit boss to get me one. He came back from the hardware with a coupling and trying with frozen hands I for the life of me could not get the coupling to thread up. The bonehead didn't know the difference and gave me a plumber's coupling. I got my own RMC coupling and it fit with no problem.

The good news is that no horses were killed...
 
K8MHZ said:
Real life experience:

Nasty, cold mid winter job at a jail. Threaded rigid coming out of wall and very hard to reach. We were out of couplings so I asked our nit wit boss to get me one. He came back from the hardware with a coupling and trying with frozen hands I for the life of me could not get the coupling to thread up. The bonehead didn't know the difference and gave me a plumber's coupling. I got my own RMC coupling and it fit with no problem.

The good news is that no horses were killed...
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Plumbers couplings are tapered, electricians couplings are straight. You are required to use a tapered (NPT aka-plumber's thread) on RMC:

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).
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mattsilkwood said:
our threader has a latch that will allow you to do straight or tapered threads.
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I would like to see that, I thought the thread was a function of the dies.
 
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