# Long shot but....



## Myfordman (10 Feb 2013)

Just thought I'd ask here.....

I need to make a single, tight radius 180 degree bend in some small bore copper pipe.

Typically 12mm radius in 6mm od tube.

Does anyone have a small tube bender and would be willing to make the bend for me.

I know I could make a bender myself but a lot of effort/time for a single bend.

TIA


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## Hudson Carpentry (10 Feb 2013)

I do have a small copper pine bender if your up this way?


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## Hutzul (10 Feb 2013)

An old method of bending copper pipe was to tightly pack it with sand, and bend it round a pin of radius required.

Or: find a spring to replace the sand but can be a pain to remove spring after.

Good luck.


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## Graham Orm (10 Feb 2013)

Tadaaaaaa! http://www.ebay.co.uk/itm/3IN1-COPP...556?pt=LH_DefaultDomain_3&hash=item5d3a3f50fc

Not sure you will get a 180 out of it. Maybe if you do 2 90's and joint it? You *might *do it with an external spring, depends how tight you want it. Or pack with sand as already stated.
*
EDIT: It says on the box 180 degree, so there you go.*


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## graduate_owner (10 Feb 2013)

For a 6mm pipe, a spring bender would slip over the copper tube, so wouldn't be an issue removing. Also, you could buy a cheap pipe bender for plumbing purposes but I'm not sure they go down to 6mm - but 8mm is used in microbore plumbing. I bought one for less than a fiver - not great quality but I only needed for the one job. If the benders and springs only go down to 8mm, could you perhaps wrap duct tape around to make a snug fit?

K


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## powertools (10 Feb 2013)

Your local small garage will have a pair of brake pipe bending pliers that will do that radius.


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## Myfordman (10 Feb 2013)

Thanks for all your replies.

Alan, what is the minimum radius that your bender can achieve please?

I've looked at the ebay bender and could not find any that stated the bend radius. They all seemed to be based on the same design and the picture would appear to have a far too large radius.

Thanks for the reminder of the sand method. There used to be stuff called woods metal that would melt in hot water and could fill a pipe for bending and be readily removed when complete.

I will pop round to my local garage and see what bend radius their tool can offer.

I'm not too happy with using 2 x 90 degree bends as the solution has to be ultra reliable and will operate above solder temperature under fault conditions so I'd have to silver solder - so far not a skill I've had much luck with.

Thanks guys


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## Spindle (10 Feb 2013)

Hi

Woods metal can still be bought - one of the popular brands is Cerrobend.

Regards Mick


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## AES (11 Feb 2013)

Can help to soften the copper before hand too. Heat up to "red" and allow to cool naturally, then bend.

Krgds
AES


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## Phil Pascoe (11 Feb 2013)

Go the other way to soften - heat to cherry red, then quench quickly.


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## Myfordman (11 Feb 2013)

phil.p":1oiyn0w6 said:


> Go the other way to soften - heat to cherry red, then quench quickly.



ReallY? So it is opposite to carbon steels then?

Learning all the time.


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## Phil Pascoe (11 Feb 2013)

Yes, if you're beating it you beat til the work hardens it, then heat, quickly quench and start all over again - just the same if you're drawing it. Brass and silver are the same. Obviously, if you're bending it you only anneal once.


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## AES (11 Feb 2013)

Gents,

I should apologise for the brevity of my post this morning.

Phil.p is quite correct, you _can_ anneal copper by heating to cherry red then quenching in clean cold water. BUT, as per my apprenticeship (many moons ago!) this could have the disadvantage of setting up stress cracks, particularly if the copper concerned was not evenly heated and/or evenly cooled (likely to be the case dealing with a length of copper pipe/tube). Cracking can also occur if the pipe is thin-walled, which I thought may be the case because the pipe Myfordman is trying to bend is quite a small OD.

The advantage of quenching in clean cold water is that any black scale deposited on the copper as a result of heating to red tends to flake off easily after cold water quenching whereas if allowed to cool naturally any scale can be a bit of a PITA to clean scale off (IF there's any present - that depends on the flame and how close to the metal it's held).

As someone else has said, if you "bash it around a lot", copper will work-harden quite quickly so it's a case of having to anneal several times if you're working the metal a lot. But I wouldn't expect that to be necessary if it's "just" a question of making one bend. But if it does start to harden half way through bending (you should feel it start to become suddenly much more difficult to do the bend) then anneal again.

As others have said, bending springs (internal or external), dry fine sand, or Cerrobend should ensure that the inside wall of the bend doesn't "kink inwards" while bending. Another trick is a length of soft iron wire if it's a tight-ish fit inside the pipe, but do leave enough wire length to be able to get a good grip with pliers or something to get the wire out again. (DAMHIKT!)

In all cases, anneal before starting the bend, obviously. And as above, take your choice between cold water quenching or air cooling when annealing.

Hope that helps and sorry if I was too brief this morning.

Krgds
AES


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## Cheshirechappie (11 Feb 2013)

One problem that will almost certainly occur is wall-thinning on the outside of the bend (especially as it's a very tight radius bend). It might be worth a test bend on a scrap piece of pipe, and then sectioning it to see if wall thickness is still adequate for duty after bending. If it's thinned too much, make the bend from thicker-walled pipe to start with - there isn't much else you can do to avoid the problem.

(AES has already mentioned the related problem of cockling on the inside of the bend. That can be reduced or eliminated by bending whilst full of sand, Cerrobend or similar, but this approach tends to exacerbate the wall thinning on the outside of the bend. A 2d bend is VERY tight, so the effect of both cockling and wall-thinning is likely to be significant.)


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## Myfordman (11 Feb 2013)

Thanks for the further contributions gents.
It is possible that I could increase the bend radius a little - I'll have to check.
Using 6mm tube is very attractive as I can use standard compression fittings on the end. 
I suppose I could use 3/16" 4.7mm tube and make my own conversion olives to put into 6mm fittings.

I could also fill the tube with soft solder prior to bending (and after annealing!)
The operating pressure will be liquid at below 2 bar and so wall thinning should not be too much of a problem.
In use it will be inside insulation and located on the roof of my house so no one will see any cockling!


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