Working with rigid

infinity said:
The dies are required to be the same (NPT) for plumbing and electrical. There is a straight thread machine tool die for but that is not NEC approved for field threads.
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But all the female threads (With some exceptions for special applications) are cut straight, NPS - National Pipe Straight
 
Eddie702 said:
Yes they do have different dies. I was told long ago they were different. Here we go again
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OK, I was told the same thing long ago, but I have never seen different dies or taps, either in the wild or in catalogs. Until I do, I will continue to doubt.

Again: Does Ridgid sell different dies or taps for pipe and for conduit? If so, what are the part numbers for hand threading.
 
TwoBlocked said:
Serious question here. Does Rigid sell different dies for pipe and for conduit? If so, what are the part numbers for hand threading.
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Back when I started in 1970 our electric shop had a set of 1/2 to 2" Rigid dies that did not produce a tapered thread ( NPT ). Was told to never lend them out but they did not explain why. Anyway one of our plumber insisted on using them. Told him that they were only for the electric shop. Guy spent a while threading pipe for a 120 # steam line. He swore I sabotaged his work but luckily another person was nearby & heard me tell him he should not use them. After that our engineer made us spray paint the die heads yellow and told the shop never to use them Believe that is the Reason you are not suppose to thread a chase nipple into a heavy wall coupling. The coupling has a tapered thread while chase nipples have a straight thread.
 
TwoBlocked said:
OK, I was told the same thing long ago, but I have never seen different dies or taps, either in the wild or in catalogs. Until I do, I will continue to doubt.

Again: Does Ridgid sell different dies or taps for pipe and for conduit? If so, what are the part numbers for hand threading.
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No NPT is NPT. Plumbing and RMC require NPT.

When I started in the 80's we used straight, non tapered thread dies (NPSM) for decades on RMC. Not sure if the taper was even required then but if it was no one enforced the taper requirement. Locknuts spin on very nicely. ;)

I think that I may still have a few threaders laying around with straight machine dies.
 
Wen I started in 73' we were told that electrical was straight threads and plumbing was tapered. And you know what? It must have been true at one time. Ridgid makes straight dies and tapered dies and always have.

If the straight dies were not originally made for electrical what were they made for?

Also some of their machine dies and threaders are made so they can be adjusted to cut straight or tapered threads with the same dies.

I still have and old Toledo die that cuts 2 1/2", 3", 3 1/2" & 4" pipe. It has an adjustment on it to cut straight threads or tapered threads.
 
hillbilly1 said:
Then how come a locknut can be threaded to the last thread on a factory conduit nipple, but not on a plumbing nipple?
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Just different tolerances. I dont think its a "plumbing vs electrical" thing, its just a different manufacturer and different tolerance thing. Ive got various 2" nipples amd locknuts in front of me and played around with them. Using several different locknuts on the same nipple, some went on much further than others. Than trying out the same locknut on different nipples, same thing. The diameter at the start or end of the threads can be different with the pitch all the same. Factory threads are likely rolled not cut.
 
Eddie702 said:
Wen I started in 73' we were told that electrical was straight threads and plumbing was tapered. And you know what? It must have been true at one time. Ridgid makes straight dies and tapered dies and always have.
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Many of us were told wrong. At the very beginning of Article 348, Rigid Metal Conduit, in the 1975 code there is a note that says:
"Note: Where conduit is threaded in the field it is assumed that a standard cutting die providing 3/4 inch taper per foot."
This is not shown as a change, so this taper would have also been found in the 1971 code.
As far as I know the male threads on rigid conduit have always been required to be tapered treads. Part of the confusion come from the fact that the conduit couplings in the US have always been straight threads. That is not the case for conduit couplings in Canada...up until the late 70s or early 80s, the conduit couplings in Canada had taper threads, just like plumbing couplings do.

There are uses for straight threads, and therefore there are dies available for straight threads.
 
electrofelon said:
Than trying out the same locknut on different nipples, same thing. The diameter at the start or end of the threads can be different with the pitch all the same.
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UL 6 for rigid metal conduit has a specific dimension for diameters at the start and end of the male threads.

However with field cut threads made on threaders like the Ridgid 300 threader, can be adjusted in the field and when you do that the threads will not not be in compliance with the UL standard. We would often adjust the threads for a tight fit in the conduit bodies. The female threads on the conduit bodies often had excess galvanizing and required a deep cut thread.

Locknuts seem to have a lot of variation in how they fit on male treads.
 
Joethemechanic said:
But all the female threads (With some exceptions for special applications) are cut straight, NPS - National Pipe Straight
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All of our couplings are straight threads, but many of the conduit bodies have tapered threads. The UL standard permits the conduit bodies to have either straight of tapered threads.
 
I wonder if water pipe and electrical conduit use something like a "Fit Class" for nut and bolt threads.

A thread fit class specifies the tightness of a thread by defining the tolerance and fit between mating external (bolt) and internal (nut) threads. For Unified (UN) threads, the common classes are 1A/1B (loosest for frequent assembly/disassembly), 2A/2B (most common for general use and balance of strength/interchangeability), and 3A/3B (tightest, for critical safety applications). The class is indicated by a number followed by a letter, where the letter specifies whether the thread is external (A) or internal
 
electrofelon said:
Yes please. Can Someone PLEASE provide a part number or document stating the difference? Or is this information locked up in fort knox ??
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According to a Ridgid Q&A from 5 years ago.

What is the part number for replacement thread dies for 3/4 and 2 inch electrical conduit? Thanks​


RIDGID_CustomerService · 5 years ago

You will need the NPSM dies.
3/4" #37965
2" #37985
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electrofelon said:
Likely a clueless person, saying to use straight thread 🙄
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I was at a NECA show about 15 years ago and a vendor was showing off a new conduit threader....but it could only cut straight threads...I asked about and he had no clue of the requirement for taper threads, and told me that the motor in this unit would not have enough power to cut taper threads on conduits larger than 1". I think it was designed for 1/2 through 1 1/2. Not sure what ever happened to the product.
 
electrofelon said:
Likely a clueless person, saying to use straight thread 🙄
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It appears to be the answer you would get from Ridgid, as it is on their company website.
Not saying it is correct per Codes and Standards but it is sufficient to keep the myth alive.

However the die part number themselves are not available in conduit versus pipe, only straight versus tapered.
 
The other reason for straight threads (I was told) that RGS going into a coupling both conduits are supposed to be screwed in far enough so the ends of the conduit would touch with no gap.
 
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