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Posted By: gfretwell Screws in EMT connectors - 03/05/14 08:39 PM
I picked up some Halex steel EMT set screw connectors.
I decided I would see if I could find some stainless hex screws for them, thinking that is an easy thing. After 15 minutes at Ace Hardware we figured out these use a M5-1.0 thread which seems not to actually exist anywhere (web search came bank no joy too).
What was wrong with the good old 8-32/10-32 or even a M5-.80?

Posted By: HotLine1 Re: Screws in EMT connectors - 03/05/14 08:50 PM
Did you try McMaster?? They have never let me down.
Posted By: HotLine1 Re: Screws in EMT connectors - 03/05/14 08:56 PM
Did you see this (from a real quick search)

"The 10-32 (10 gauge, 32 threads per inch) is very close to the M5x0.8 mm/thread. The 1/32-inch thread is 0.03125 inch per thread. Multiply by 2.54 cm/inch and you would get 0.794 mm per thread, which may be tolerably close to 0.8 mm of the metric screw. As already noted, the 10-gauge screws major diameter of 0.1891is going to be slightly smaller than 0.19685 of the 5 mm screw (by approximately 8 thousandths). Since a "tight fit" is in the range of 2 thousandths, you will have trouble torquing the wrong sized screw into a 5mm threaded hole or nut. "
Posted By: Tesla Re: Screws in EMT connectors - 03/05/14 09:36 PM

You'll have a quicker time reaming out the holes and re-tapping them to suit.

I am puzzled. If the bodies are common steel -- how can SS provide advantage?


American engineers use 'threads per inch' as a metric.

European engineers adopted 'millimeters per thread' as a metric.

This is why Hotline's math was necessary.

It's also why the ordinary Joe is stumped when looking at metric fasteners.

At first blush, it's not obvious which thread is coarse or fine.

M5x0.8mm is going to be 'finer' than M5x1.0mm.

Most of the metric threads on sale in America are destined for the automobile -- hence FINE threads.

In our trade, most of the threads are coarse:

10 x 24 versus 10 x 32
1/4 x 20 versus 1/4 x 28
5/16 x 18 versus 5/16 x 24
3/8 x 16 versus 3/8 x 24

So I'm not surprised that M5x1.0mm is scarce.
Posted By: gfretwell Re: Screws in EMT connectors - 03/05/14 10:48 PM
The 10-32 screws rattle around in the hole. I think they would just strip out if you tried to get them tight.

I was actually surprised that I did not find them on a European or Asian web site tho.
These connectors are Hecho en India. Maybe it is an old BA size or something.

Tesla, the connector is galvanized and I am painting it but the screws are just common steel. They will rust in place and you will never get them out if you want to.

BTW this is not going to be a raceway, I am making a frame for a canopy awning. EMT just seemed to be a handy material that I had the tools to work with.

The screw in the center is the one I am going for.

[Linked Image from]
Posted By: Tesla Re: Screws in EMT connectors - 03/06/14 01:20 AM
It's actually possible to use Locktite as anti-seize compound. (don't use red)

Perhaps Locktite Green 290

Perhaps Locktite Blue 242

" It protects threads from rust and corrosion and prevents loosening from shock and vibration."

A single tube should be enough for your entire project.

It's also to be recommended for set-screws in hole saws and such. (Green 290)

I'm not a paid spokesman, BTW.
Posted By: gfretwell Re: Screws in EMT connectors - 03/06/14 03:58 AM
I just went with the manufacturer's screws and a good coat of paint. I am going to hit it again now that it is up to get any dings. I guess if I need to take it apart I will use my grinder wink

In the end it is just $40 worth of pipe and a half dozen brazing rods.

[Linked Image from]

Posted By: HotLine1 Re: Screws in EMT connectors - 03/06/14 04:20 AM
Nice job Greg!!
I'd put a smiley here, but I don't have them.
Posted By: gfretwell Re: Screws in EMT connectors - 03/06/14 04:45 AM
I am still confused by exactly what size screws these are. They appear to be M5-1.0 but that does not seem to exist. It is not an SAE thread so that leaves me thinking it is something they use in India that nobody else knows about.

I guess it is time to ask Halex tech support.
Posted By: Tesla Re: Screws in EMT connectors - 03/06/14 05:22 AM
ISO / Metric ==> M5 means metric 5 millimeter.

ISO 261:

ISO 262:

0.5 is deemed FINE

0.8 is deemed COARSE

As you might imagine, the global manufacturing trend has caused even American manufactures to shift over to metric.

The pitch of 1.0 mm in an M5 fastener is a non-standard type.

Posted By: gfretwell Re: Screws in EMT connectors - 03/06/14 08:58 AM
I got a response from Halex and the lady who answered said she will find out what kind of screw it is.

Posted By: gfretwell Re: Screws in EMT connectors - 03/06/14 09:03 AM
I am thinking it might be a #12 but the pitch does not seem to be 24 tpi.
I may still have some 12-24 screws around here somewhere. They were standard for 14" racks.
Posted By: renosteinke Re: Screws in EMT connectors - 03/07/14 01:12 AM
I'd like to point out that there is absolutely no reason for a manufacturer to use any 'standard' thread. If you look closely at many household items, you will find threads in -literally- every shape and size imaginable. ou might as well put up that Machinery's Handbook.

With zinc being quite malleable, there is also no real need for the screw to match the socket very closely. I would not be surprised if the rough zinc casting had a plain hole, that the screw was forced into while the zinc was still quite soft. Voila! Perfect fit!
Posted By: gfretwell Re: Screws in EMT connectors - 03/07/14 02:43 AM
I heard back from Halex. 12-24 it is.
Posted By: NORCAL Re: Screws in EMT connectors - 03/07/14 08:14 AM
12-24 is a common size on telcom racks, also was used on the now discontinued ITE Vacu Break NEMA 1 HD safety switches cover interlock, found that out when trying to replace a missing cover screw, otherwise a oddball thread size.
Posted By: HotLine1 Re: Screws in EMT connectors - 03/07/14 08:25 PM

This link has what you want,

They used to 'sell' loose quantities, albeit a higher price then the 'box' cost.
Posted By: gfretwell Re: Screws in EMT connectors - 03/07/14 10:37 PM
They still have a fairly limited selection in stainless 12-24.
I am just going with the ones Halex gave me.
Posted By: Texas_Ranger Re: Screws in EMT connectors - 03/10/14 09:12 PM
I did a quick Google search and it seems that M5x1.0 was indeed used for a few very obscure applications like old Peugeot bicycles but is insanely hard to find nowadays. You do encounter weird screws from time to time... a while ago I installed some Italian receptacle boxes (they have listings for all European countries and you can get receptacles to every standard so they're sold in Austria) and needed longer screws in a kitchen with thick tile. The originals look like a very coarse M3.5 and I couldn't find them anywhere. I ended up using M3.5 sheet metal screws.
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