Dom – if it really is antique then it could be just about anything as there were few if any standards way back.

You will have to take accurate measurements of diameter and pitch of the thread and go from there. It could be either metric or imperial so "about 10mm in diameter" won't do, is it 10 mm or 3/8 inch or something else. As to it being finer than an M10 thread then I'm not surprised as most threads on the outside of tube are, but you've a whole range to choose from, British standard pipe (BSP), British standard fine (BSF), Brit. std.cycle (BSCY), Brit std. brass (BSB) to name a few, as well as the American equivalents and any other Continental varieties that were going at the time. There are also threads that were used mainly on electrical stuff such as BSC – Brit. std. conduit.

Keith

As Michael says those are the common threads for light fitting sbut it could also be a PG thread which is used on conduit and that has a 10mm size, work out the pitch and an exact dia to grt a better idea of what you have.

There was also a French Standard "FS" thread but I think that is a bit coarse for use on tube.

Ideally need a thread guage or two, metric and imperial.

Most studs are undersize to make sure they go in, so could be approaching the imperial 3/8". Other problem the difference between cycle thread 26tpi (Threads Per Inch) and 1mm pitch is 0.6mm or 25.4TPI metric so holding a guage up will both look extremely close. Other factor is a difference in angle of the threads and very hard to see on 1mm pitch or lower but doable.

M10X1 is a common thread size so is M10x1.25, course is M10X1.5. Love 1mm pitches.

But no more likely than anything else. Although you no doubt mean well I do not think this kind of comment, based on two tenths of nothing, is helpful.

Michael Gilligan has it right.

Edited By Clive India on 17/05/2015 09:35:28

I forgot to mention, are you sure its brass, what I mean is it was quite common to use steel with brass sheet wrapped around it, and each end of the sheet was tucked into a slot running the length of the bar, this can be a trap if cutting and rethreading, as its easy to catch the brass and pull it from the slot. Just try a magnet on it.

Ian S C

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Dominic,

Jason could well be correct with 1/8" BSP … but may I just do a 'sanity check' ?

[Apologies if this sounds patronizing, but it's best to ask]:

Are you counting the "pitches" correctly ? … i.e the first mark is 'zero' not 'one'.

… It's a very easy error to make:

I always remind myself that we're counting 'fence-panels' not 'fence-posts'.

MichaelG.

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1. Yes it looks like a nominal 10mm fine thread … which is what we might hope.
2. British pipes are specified by their bore, not their outside diameter. This is very logical, given the purpose of a pipe ; but it does cause confusion. [note that in domestic plumbing, the old 1/2" copper pipe is bigger than the new 15mm.]

hope it all goes well

MichaelG.

To age brass just hang in the fumes of ammonia, NB not in the liquid! Ammonia easily bought as household cleaner. But how you suspend a long rod in the fumes is up to you. After a few minuets a black surface appears ,wipe with a rag and looks like old brass.

After cleaning the brass of old lacquer, grease and muck, there are a few ways of ageing it. First is salt water, this will take a few days. Next is vinigar, you can just dunk it and leave it out in the air, then repeat until you get the right colour, or get a sealable container, put some vinigar in the bottom, suspend the brass above this, and seal the container. The container could be a bit of plastic pipe. The same could be used with Ammonia.

You need to wear gloves to prevent contaminating the metal.

You can buy a product to antique brass.

Ian S C