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Marvo

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I'm hoping a few of the older members might remember this. I need to know what the standard wall thickness used to be for the very old type threaded steel conduit (20 and 25mm equivalents). I'm guessing the diameter and wall thickness was in imperial sizes so I also need to know what the newfandangled metric equivalent steel tube sizes would be. Also for good measure does anyone remember what the thread specifications were? Was it taper threads or parallel and any idea of thread pitch or TPI specs would be great.

Thanks in advance.
 
1/8".....which would be the equivelant to 3mm....
but you need to remember that its the bore on british thats measured....OD on metric....hense the `strange` sizes for BSP taps n dies...but thats pipe sizes anyway......
it may not be the case for conny....
 
God your asking something now!! lol!! I can't remember the wall thickness of either the standard or heavy duty screwed conduits. I can tell you that they weren't tapered threads though, that's the American standard for their conduit!!

There are converter's available (or used to be) from the old 3/4''/1'' to metric 20mm /25'' though. And i guess for other lager sizes too...
 
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they do that so there's a chance of it fitting somewhere up the thread.
 
they do that so there's a chance of it fitting somewhere up the thread.
Lol, that might be tongue in cheek but it's probably the truth :)

I'm pretty sure the installation that's going to be giving me headaches will have been done to old British Standards rather than US standards. The entire installation is threaded. I have a threading machine but I'm concerned I might not have the tooling to cut the old threads, especially if they were tapered which thankfully it sounds like they won't be. I'll need to sourc some new pipework and I wasn't sure whether I'll need to make up some adaptor couplings and do the new stuff in metric threads or whether I can just continue with the original threads on the new pipe but wall thickness could be critical.

I'd rather use the original threads on the new installation because many of the very old light fitting and other fixtures screw directly on to the conduit tube.
 
why not fit adaptors to the imperial conduit then do your new work in metric?
 
Adapters are an option but there's other complications with fitments that we'll need to reuse that screw directly on to the old conduits threads.
 
Also much of the conduit installation is visible as will be our new installed areas. I'm not sure welding is going to be an option because the high standard of cleaning up is really a workshop job for us, we're not really geared up to do that on site.
 
Lol, that might be tongue in cheek but it's probably the truth :)

I'm pretty sure the installation that's going to be giving me headaches will have been done to old British Standards rather than US standards. The entire installation is threaded. I have a threading machine but I'm concerned I might not have the tooling to cut the old threads, especially if they were tapered which thankfully it sounds like they won't be. I'll need to sourc some new pipework and I wasn't sure whether I'll need to make up some adaptor couplings and do the new stuff in metric threads or whether I can just continue with the original threads on the new pipe but wall thickness could be critical.

I'd rather use the original threads on the new installation because many of the very old light fitting and other fixtures screw directly on to the conduit tube.
if you are using metric then your dies will be as such......as i says BSP is a different threadform and what you`v got to remember as well is because british was on the bore.....what amounts to...say a 1" BSP die will have to take into account the wall thickness of the pipe....so the die is actually 1 1/4"...if you get an internal with a set of verniers.....
 
Time to get your Thread Gauges out!

I can only disturb the installation when the works program starts, removing even a sample isn't as easy as it sounds. I was just hoping to get possible info to organise any necessary tooling in advance and cover as many bases as possible.
 
fair enough.....i just know that tapered threadforms are used on gas fittings.....
you can get BSP tapered n all...
the americans use NPT...national pipe thread...

And probably why they only use they're seamless heavy duty conduit in hazardous area installations!! lol!! It's similar to what we used to call our seamless HD conduit , ...''Barrel'' conduit.

There is a difference in physical size between Yank conduit and UK imperial/metric conduit. Pretty sure they size by internal bore where the UK sized on OD. To be honest it's been a very long time now, since using American conduit. What i can remember is, that the 3/4'' doesn't fit UK knockouts on metal back boxes, they had to be drilled out bigger, and the lock-nuts then hit the back box accessory screw lugs!! Cost the contractor a lot of time and money, as the best part of the initial system was pulled out and his conduit stocks replaced with metric conduit!! lol!!
 
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Also much of the conduit installation is visible as will be our new installed areas. I'm not sure welding is going to be an option because the high standard of cleaning up is really a workshop job for us, we're not really geared up to do that on site.
get all the crap and galv off the end....and just run a fillet in with a low hydrogen rod.....weld it lovely that will as low hydrogens tend to `freeze` dead quick....so you wont get any drop off......
 

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