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Metric threads #142192 12/17/04 05:41 AM
Joined: Sep 2002
Posts: 1,497
C
C-H Offline OP
Member
"They" have started to sell cable glands etc. with metric thread instead of the Pg conduit thread. This is driving us nuts! When making changes and additions to equipment we installad earlier, noting fits. It was bad enough before to find conversions from Pg 29 to Pg 21. Now we need conversions from PG 29 to M25... Doesn't exist, it seems. [Linked Image]

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Re: Metric threads #142193 12/17/04 09:20 AM
Joined: Oct 2002
Posts: 177
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Belgian Offline
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Same here. Changes were made already 1 year ago and all type of new conversions have sprung up together with the changes.

Re: Metric threads #142194 12/18/04 08:32 AM
Joined: Aug 2001
Posts: 7,520
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pauluk Offline
Member
Careful, C-H, you'll be joining us Brits in the anti-metric campaign! [Linked Image]

In domestic installations, this is still a problem with fixture screws: M3.5 supplied with new accessories vs. 4BA threads on 1960s boxes.

Re: Metric threads #142195 12/18/04 01:45 PM
Joined: Jul 2002
Posts: 8,337
Trumpy Offline
Member
C-H,
I can't say that I've ever liked the Pg sizing system, for cable glands and so forth.
I've always found the Metric threading sizes a lot easier to use, but that's only my personal view!. [Linked Image]
Oddly enough, (and I really hate to play the EU card here) there is (like for other things) an EU Directive on Cable Glands and the like, it's called prEN 50262, but I have a feeling it may apply to more than just Cable Glands.
I didn't dare do a web search on it, for fear of getting lost in the technical data!. [Linked Image]

Re: Metric threads #142196 12/19/04 10:06 AM
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pauluk Offline
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Re: Metric threads #142197 12/19/04 10:54 PM
Joined: Dec 2002
Posts: 1,250
D
djk Offline
Member
Moving to standard systems, metric or otherwise, makes life a lot easier and will open up new product ranges to everyone in europe.

Plumbers in the UK and Ireland face metric-imperial problems regularly. Old fittings in this part of the world not being metric.

Re: Metric threads #142198 12/22/04 04:36 PM
Joined: Dec 2001
Posts: 2,486
T
Texas_Ranger Offline
Member
Just learned it at school today. Copper pipes are metric here, steel pipe is inches. Don't knwo about the threads used though.

Have to admit I never cared about electric box threads that much... I've only seen threads on IP44 or 55 surface mount boxes and there I always used the provided glands and that was all.

Re: Metric threads #142199 12/23/04 06:59 AM
Joined: Sep 2002
Posts: 1,497
C
C-H Offline OP
Member
The problem starts when you have holes or hole making tools for PG and go metric. A 47 mm punch is no good when the glands are either M40 (40 mm) or M50 (50 mm)...

More annoying is the fact that an M40 from one manufacturer hasn't the same inner diameter as an M40 from another manufacturer!

Still, the metric is better than the PG (fewer sizes to cover the same range) but currently this all seems in limbo... [Linked Image]

Re: Metric threads #142200 12/23/04 08:18 AM
Joined: Jul 2002
Posts: 8,337
Trumpy Offline
Member
Hang on a second C-H,
The PG (Plastics Gauge) was invented in Italy, so that could explain the wayward sizes.
Another point that Ragnar touches on is this:
  • In some places Electrical conduit gives the inside diameter of the conduit, in other places, it's the outer diameter, it's the same here with water pipe.
  • Plumbers here still use Imperial sizing on pipes, as do Refrigeration Engineers, regardless of wall thickness.

I size the hole-saw to the size of the outer diameter of the thread of the gland.
I've worked on gear to IP68 (Continuously Submurged to 8 metres) and I haven't had a leak yet!. [Linked Image]

Re: Metric threads #142201 12/24/04 02:41 PM
Joined: Sep 2002
Posts: 1,497
C
C-H Offline OP
Member
We do some plumbing as well (coolant water for machinery) and the funny thing is that most of what we use is 1/2" connections. That includes the gear that comes from Germany and Japan. The only exception is the American manufacturer of the plumbing parts: for some parts only metric threads are offered! The logic of this wonderful world... [Linked Image]

We have a box marked "Weird brass fittings" where all unidentified threads go, like metric and NPT.

BTW, can someone explain why a 1/2" thread has a diameter of about 3/4"? [Linked Image]

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