1/2" Conduit Fitting Threads ??

[dalmatiangirl61]

I'm trying to figure out what tap I need to tap a hole that a 1/2" EMT Conduit fitting will thread into, this is a standard electrical fitting with the thin nut, normally used on sheet metal, I need it to screw into 1/4" thick steel. A 3/4-16 is too small, a 7/8-14 is too large. After 2 hours of searching shop I cannot locate a standard thread pitch gauge, just 3 metric sets and none match the fitting. Looks like 4.5 threads per 1/4", so maybe its 16tpi? Major diameter of the threads on the fitting is .800 , is this a proprietary thread? Maybe I should be using a different fitting?

 

[crazygoat]

Maybe this help.

https://mrelectrician.tv/1-2-16-electrical-conduit-dimensions/

 

[dalmatiangirl61]

I looked at that site, not seeing the answer there, if you see it please let me know. Major diameter of my 7/8-14 tap is .885", which I think would be a sloppy fit? My 3/4" pipe tap falls thru the hole, can't find a 1" but suspect its too big..

Edit: Put my readers on so I could actually reads sizes on pipe taps, hmm, maybe I need to find the box with the rest of the pipe taps

 

[Video_Man]

I believe this is a 1/2 inch NPT (tapered pipe thread). My 1/2in NPT tap exactly fits a 1/2" EMT retaining nut and the matching die fits the male threads....

 

[dalmatiangirl61]

I believe this is a 1/2 inch NPT (tapered pipe thread). My 1/2in NPT tap exactly fits a 1/2" EMT retaining nut and the matching die fits the male threads....

You are most likely correct, I was trying to read taps by braille, what I thought was 3/4 was 3/8, LOL

I need more lighting in here, that bracket is for a lighting fixture.

 

[kevin johnson]

Electrical threads do not have the taper of NPT. This allows for gases to escape for explosion proof installations. The 1/2” is still 14 TPI. Just don’t bottom your 1/2” NPT out. Tap shallow.

 

[wood2steel]

Conduit fittings

Keep in mind; those emt fittings are sometimes threaded with straight threads. Most pipe taps come in tapered style as well as straight design. I believe those fittings will require straight taps. I hv a collection of both in the smaller NPT size

I believe this is a 1/2 inch NPT (tapered pipe thread). My 1/2in NPT tap exactly fits a 1/2" EMT retaining nut and the matching die fits the male threads....

 

[wood2steel]

Kevin, You hit the nail on the head. I tap conduit fittings in my building all the time with those straight pipe taps. Never knew about the gas venting requirements!!

 

[rons]

That is a second. I'm looking at one of those 1/2 EMT threads and a 1/2-14 NPT tap. I remember that the cost of that OSG tap was ... hurtful.

 

[crazygoat]

I agree on it being a straight thread. I believe you can run the NPT tap all the way thru the hole.

 

[rons]

Keep in mind; those emt fittings are sometimes threaded with straight threads. Most pipe taps come in tapered style as well as straight design. I believe those fittings will require straight taps. I hv a collection of both in the smaller NPT size

Straight threads are the neatest but won't seal like a tapered thread. But me thinks that the thread distance is so small that it doesn't make much difference.
But there is a difference.

 

[Bondo]

You can tap with a NPT tap and just ho in as far as you want to the threads bottom out so it is a flush installation. Or you can go all the way through with the tapered tap and make straight threads. Though you will have to drill a lightly larger hole for it.

Sent from my SM-G960U using Tapatalk

 

[kenton]

1/2 NPS?
More characters.

 

[Video_Man]

NEC 344.38 "..........Where conduit is threaded in the field, a standard cutting die with a 1 in 16 taper (¾-in. taper per foot) shall be used.

(That's NPT, and generally refers to heavyweight conduit that normally comes factory threaded.) However, the EMT threaded box connectors I have appear to also be tapered. Straight joiners are not taper threaded. The thin retaining rings only have 2-3 threads so are difficult to assess.

 

[dalmatiangirl61]

A hardware store 1/2" npt tap did the trick, but ruined the tap. It was made in Japan, figured it would be decent, guess I need to splurge on a new set of Vermont taps.