bending 4mm copper tubing

[Clive HartlandParticipant @clivehartland94829]

Any one know how to get a nice bend/curve on 4mm copper tube?

I have tried spring tube benders and it kinks and I now contemplate lead filling.

Do I make a tube bender?

Clive

[Clive HartlandParticipant @clivehartland94829]

Difficulty bending to a nice curve

[Nathan SharpeParticipant @nathansharpe19746]

Hi Clive, Have you tried a brake pipe bender? Cheap off ebay.

Nathan.

[mgjParticipant @mgj]

I have a tube bender – Hemingway. Very good, but over complex for the task- but quite excellent in the slightly larger sizes of tube.

If i'm not telling my granny, the operational guts of the thing is a groove, just over 1/2 th dia of thee tube to be bent. That stops it going oval and collapsing. So a lot of my smaller tubes I bend by using a ball nose cutter on a rod of the required bend radius, of about 75% dia depth, and bend the annealed tube around that.

3/16 tube I like the sliding shoe of the bender, but less than that a thumb and a groove does as well!

[Michael GilliganParticipant @michaelgilligan61133]

Don't know if it's still available, but Record did a "Mini Pipe Bender" in cast Alloy [painted Blue, of course], for tubes around this size.

Alternatively … fill with Wood's Metal, not Lead; it melts at at about 80°C

MichaelG.

Edited By Michael Gilligan on 08/08/2012 23:42:23

 

Looks like the Record is still available … at a price!

Edited By Michael Gilligan on 08/08/2012 23:47:05

[Clive HartlandParticipant @clivehartland94829]

It looks like I will make a mini Pipe bender as part of the exercise. I will need one for a later job anyway.

Clive

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Clive ,

Far better to use lead wire than pour lead in . Lead wire is easy to make in any size – just cold forge to rough size and pull through a hole to finish .

A good substitute for lead wire is heavier type plastic coated electrical wire . There are so many sizes available that something sutable can usually be found .

Always best to bend in a grooved aluminium former .

Tubes bend easier and more cleanly if the wire and the former are well greased ..

Regards ,

Michael Williams .

[Clive HartlandParticipant @clivehartland94829]

The specified bend is 4mm Radius so it is pretty tight bending with 4mm Dia. copper tube.

Its a bending jig for sure, I will start on it this evening when it is cooler as the sun is right in the front of the workshop.

Clive

[paul raynerParticipant @paulrayner36054]

I have read somewhere if you pack tube with dried sand and

seal the ends up you will get kink free bends, although I would

imagine in small bore pipes it may prove difficult to remove all the

sand.

[mgjParticipant @mgj]

Clive – 4mm rad in 4mm pipe is seriously tight. That will be an entertainment. I think you'll need the extra leverage of a bender to do that nicely.

There is a sort of ideal (typical) minimum dia/bend rad ratio. I have forgotten what it is, and someone may be able to help with that – but its not 1:1!!!!

Any way you can get away with it a bit wider than 1:1?

[DMBParticipant @dmb]

Clive, try Chris Heapy`s site. I think he does a table of sizes, pipes/radii etc.. If not, root around various sites run by individuals, because I`ve seen it somewhere!

John.

[VersabossParticipant @versaboss]

Posted by paul rayner on 09/08/2012 16:46:25:

I have read somewhere if you pack tube with dried sand and

seal the ends up you will get kink free bends, although I would

imagine in small bore pipes it may prove difficult to remove all the

sand.

Very true, Paul.

A colleague tried to make a helix coil from 10 mm copper tube. The diameter of the coil was around 50-60 mm (from memory). He tried filling with sand and was unable to remove it afterwards. Then he had a brilliant idea: he filled the tube with table salt… Just put it in a bucket of water afterwards, and away it is. At the softening temperature of copper the salt does not melt. That way he produced a perfect coil.

Greetings, Hansrudolf

[Michael GilliganParticipant @michaelgilligan61133]

Clive,

You might find some useful guidance here

… He's talking slightly bigger sizes than 4mm, but the principles are explained.

MichaelG.

 

As I mentioned earlier … Wood's Metal, or similar, is the best option for filling.

I think the Plumber's version is called CerroBend … see here

 

 

Edited By Michael Gilligan on 09/08/2012 22:46:30

Edited By Michael Gilligan on 09/08/2012 22:59:41

[Michael GilliganParticipant @michaelgilligan61133]

Clive,

There is a very neat tube bender, described in photo's and a drawing, here

MichaelG.

[mark mcParticipant @markmc72333]

I've heard of people filling the pipe with water and freezing it then bend

[Clive HartlandParticipant @clivehartland94829]

Thanks for that lead Michael, I have downloded the drwg and will study it to see if I can machine it with what I have.

Mark, I have taken that on board as my freezer is right alongside my workbench.

Clive

[FMESParticipant @fmes]

Hi Clive,

I use a product called 'Cerrobend', it looks like lead but melts in boiling water – just melt and fill the pipe, bend and a quick touch with a small torch melts it all out again for reuse.

Hope this is of use

Lofty

[nigel jones 5Participant @nigeljones5]

for ultra cheap you can fill it with water then put it in the freezer – work quickly once removed though!

[Clive HartlandParticipant @clivehartland94829]

I have made a bender to an American design but its as good as useless on the 4mm tube even when annealed.

I am now looking at one with a grooved bar that goes around with pipe as you bend it. I will still have to make it and I just need a little more time before I start. One of the main problems is the pipe is pulled through as you roll the wheel around. See my photos as there is a pic. of it there. This seems to make the rad. larger than what i want.

Clive

Edited By Clive Hartland on 04/11/2012 22:50:26

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Clive ,

Didn't know you still had problems . Bit of a rag bag collection of thoughts but here goes :

(1) For any given tube diameter and wall thickness here is a lower limit to the radius that it can be bent to by 'simple' means such as benders and formers – below that limit it isn't going to happen .

(2) Very tight bends in aerospace pipework are hydroformed – the pipe is filled with pressurised oil and then bent by two dies closing against each other in guides ( like press tool dies ) – one with outside curvature and one with inside curvature and both radiused concave to the tube to match the tube diameter . Pressure is maintained throughout at a high enough level to balloon the tube into the internal shape of the dies .

In model sizes die forming could work quite well in a simpler form .

(3) In traditional copper smith work as found on steam engines very tight bends were sometimes made rather roughly by bending but more commonly by one of several varieties of coppersmiths joint – basically sophisticated cut and braze methods .

The most common method is to cut a row of orange segment cutouts in the tube where the inside of the radius is to go , fold up and braze .

I have done this on 3/16 tube and it went well . Need some scrap tube to work out the shape of the cut outs by trial and error and then it is easy to do the finished part .

Some of the pipework done this way in full size is beautiful to see – the cutouts are hardly visible and the whole joint is blended together into one flowing curve .

Regards ,

Michael Williams .

[John Ockleshaw 1Participant @johnockleshaw1]

Hello Clive,

Commander W.T.Barker described a tube bender in Model Engineer number2383, 9th January, 1947.

It is for small copper tube up to 1/4" diameter maximum with a centre line radius of 1 1/2 to 2 diameters minimum. A anchored mandrel supports the inside of the tube at the point of bending.

I made one years ago and it does a first class job.

If you do not have access to the issue I can email you a copy of the article.

Regards, Graham

[Clive HartlandParticipant @clivehartland94829]

Graham, can you contact me through PM's and I can give you my email addy there.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Clive Hartland on 09/08/2012 14:35:18:

The specified bend is 4mm Radius so it is pretty tight bending with 4mm Dia. copper tube.

Clive,

It will be very interesting if you do manage to achieve this.

With the notable exception of Michael Williams' Cut & Shut … Every design, or method, mentioned so far seems to indicate that 1.5 diameters is a realistic minimum for the bend radius.

Please could you post some pictures of your experimental results?

Also …if/when you do succeed; I think it would make an excellent subject for an article in MEW.

MichaelG.

[John Ockleshaw 1Participant @johnockleshaw1]

Hello Clive,

I know I am backward but how do I go about sending a PM please.

Regards, Graham

[Clive HartlandParticipant @clivehartland94829]

If you go into, 'My Messages ' you will be able to send me a message. I have sent you one already with my email addy, the 'My messages' should be highlighted on on your Account box with the avatar in it.

I think the idea of small segments cut out might be the answer as the two bends I have made at the moment  are out of proportion to the scale and look of the engine. Also because of the larger radius they will not come in line and stick out from the outline of the engine, this is why I am trying to get a nice radius to finish it off.

Clive

Edited By Clive Hartland on 05/11/2012 08:57:25

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