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Author Topic: How to bend copper into a tube shape.  (Read 3968 times)
Fenwick Tesla-Smythe
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Dirtysockcooker
« on: July 10, 2012, 04:16:04 pm »

I'm making a walking stick and I have a piece of copper I want to mould around it to hide a flaw.  The stave is perfectly round.   I have managed to bend the copper into a closed c position but I can't get it to close.   I tried clamping it and that failed.   Someone has suggested heat, but is there a way to do it without heat?
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Mécanicien de Vapeur
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« Reply #1 on: July 10, 2012, 04:46:49 pm »

What thickness of copper sheet are you using? And what diameter is the stave??

You might need to roll the copper sheet into a tighter tube than the stave diameter, then 'spring' it onto the stave, where it should close tightly around it. But that depends on the design of the stick as to whether it's possible to roll the sheet 'off-stave' and spring it on.

And how are you rolling the copper sheet?

I've access to a set of rolling bars via my local model railway club - very useful bit of kit for cold rolling thin metal sheet. Cheaper/more DIY alternative would be to use a thick layer of newspapers and a suitable dowel. Lat the sheet on the layered newspaper and roll the dowel across the sheet, pressing down firmly. Takes some practise to get things square across the sheet, and isn't that useful for tight radii (or indeed, making tubes), but would at least get the piece started.

Application of heat would make working the metal easier - it's the metal's natural temper (it's hardness/springiness) that you're fighting against. Heating the metal in the right way (annealing) makes the metal easier to work.
« Last Edit: July 10, 2012, 10:04:49 pm by Mécanicien de Vapeur » Logged

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Dirtysockcooker
« Reply #2 on: July 10, 2012, 06:35:09 pm »

Thanks for that.  It;s not very thick copper.  I will try the tighter wind thing.
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Ravenson
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« Reply #3 on: July 10, 2012, 08:59:50 pm »

is it passable that you have bent the metal far enough that you have work hardened it?  If you have it will make it harder to bend.

JJ
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Dr cornelius quack
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« Reply #4 on: July 11, 2012, 10:40:47 pm »

A good way to get a tight fit when rolling copper round a circular form is to clamp using a number of Jubilee clips.

http://isearch.avg.com/images?s=sideNav&cid=%7bE39172E6-0704-41BD-9747-B5FF23FF41BE%7d&mid=9ebaa8cef5fd47d1a9356939b28f595c-38616009d5465ea8eb3a1018d3a11c6fc79f39dd&lang=us&ds=AVG&pr=pa&d=2011-12-10+11%3a02%3a09&v=11.1.0.7&sap=dsp&q=Jubilee+clips

The full length of the tightening screw thread means that you can wind the clip till the copper is completely snug to the surface.

If you are rolling the sheet over a metal form, then you can solder up the seam, remove the clips and finish the soldering at the places where the clips were in two stages with no danger of the original joint coming apart.
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« Reply #5 on: July 12, 2012, 01:38:02 am »

Heat can be used in many ways, for you to have bent copper almost back to itself, you have most definitely hardened it.  So soften it back to a more bendable state, simply remove it and toss it on top of the range, just needs to heat to a dull red in the dark.  After that you can take it off, bend it to the final shape you need (closed), then polish it brightly.  If you want you can research copper patina methods and make it some interesting colors, or engrave, etc.

note, once it is heated fully, you can either quench(cool) it in water, or let it cool off in the air.  Neither will make a difference to how soft it becomes. 
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Ravenson
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« Reply #6 on: July 12, 2012, 06:42:31 am »

Quinlin so is not possible to harden Copper by heating it and letting it cool?Huh  I thought I had read some where that heating it up and letting it cool slowly would harden it and if you wanted to soften it you needed it to cool fast, as in Quench it?   I must read up on this...

JJ
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Captain Shipton Bellinger
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« Reply #7 on: July 12, 2012, 07:23:13 am »

Quinlin so is not possible to harden Copper by heating it and letting it cool?Huh  I thought I had read some where that heating it up and letting it cool slowly would harden it and if you wanted to soften it you needed it to cool fast, as in Quench it?   I must read up on this...
I'm afraid not; Captain Hopkins is quite correct.

As copper is mechanically worked by hammering, bending, rolling, drawing or whatever, it becomes 'work-hardened' and rather brittle due to changes in the crystalline structure. It may be softened again by annealing to red heat, which evens out the crystalline structure once more. The softness achieved depends upon the amount of heat applied rather than the time taken to cool down, so quenching or allowing to air cool has no effect on the final softness/hardness.

This is also largely true for copper- and silver-based alloys.

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« Reply #8 on: July 12, 2012, 08:32:29 am »

Quinlin so is not possible to harden Copper by heating it and letting it cool?Huh  I thought I had read some where that heating it up and letting it cool slowly would harden it and if you wanted to soften it you needed it to cool fast, as in Quench it?   I must read up on this...

JJ

Copper and copper alloys are hardened by mechanical stress (hammering, bending, etc.), and annealed (softened) by heating to relieve that stress. Rate of cooling has no effect.

Carbon steel, on the other hand, will quench-harden; this is probably what you read about. Steel is iron with a small amount of carbon mixed in, and it is this combination which is responsible for this behaviour — the more carbon the steel contains, the tougher it is and the harder quenching makes it. Low-carbon steel is resilient when annealed and tough when quenched; medium-carbon is tough and becomes hard when quenched (good for cutting softer metals); high-carbon steel is already quite hard, and quenching can make it brittle enough to break when dropped. Cast iron contains even more carbon, and is brittle straight out of the mould, and I seem to recall that pure iron will not quench-harden at all (although I really don't know if I recall this correctly.)

Carbon steel must be brought to red heat, then cooled as quickly as possible to harden. Carbon steel will also work-harden; it can be annealed by being brought to red heat, then cooled as slowly as possible (eg. buried in sand or wood ash); it can also be annealed or tempered (partially softened) by heating just until the surface oxide layer changes colour (the degree of colour change indicating the degree of softening) and then quenching, which does not cause hardening from lower temperatures.

Short version: carbon steel hardens when quenched from a sufficiently high temperature; copper alloys soften when heated to a sufficiently high temperature and do not harden when quenched.

That's probably far more info than you were looking for, but I hope it's of some use to you.
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Fenwick Tesla-Smythe
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Dirtysockcooker
« Reply #9 on: July 12, 2012, 06:53:52 pm »

Thanks for the metallurgy knowledge!

To the cooker!
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Ravenson
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« Reply #10 on: July 15, 2012, 12:04:16 am »

That is cool you learn something New every day.   I thought I had heard that Ferous metals (Iron and steels) you hardened by heating up and then cooling them fast (AKA quenching) or if you where trying to soften them heat them and let them cool very slowly.  For Non ferous metals ( copper, silver) I thought it was the opposite to harden them heat and let cool very slowly Or work harden them and to soften them heat and cool fast.  I do not remember where I heard this from.  It was many years back (15 +) when I was playing with blacksmithing.   You might be right tho I could have confused them lol after 15 years my memory is fuzzy.   Of course it could be just old age.....They say memory is the second thing to go.....I can not remember what the first thing is LOL.

JJ
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Steelheart
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« Reply #11 on: July 17, 2012, 11:27:23 pm »


[/quote]
 and I seem to recall that pure iron will not quench-harden at all (although I really don't know if I recall this correctly.)[/quote]

That is indeed correct. Pure iron is softer than aluminum. However it is really hard to get pure iron when smelting as carbon easily gets introduced into the process. I have never seen a large enough piece of pure iron to try to shape, although I have machined sintered iron.
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Uncle Arthur
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« Reply #12 on: July 19, 2012, 11:56:06 pm »

Wrought is about the only thing approaching "pure" iron that one is likely to come across commonly. It is far from pure as it contains silicious slag and a number of trace elements including a very low percentage of carbon.  It will not quench harden. Neither will mild steel to any appreciable extent.  I am not sure ifany wrought is being produced any more. I get what I use from old wagon tires, tie bands from wooden silos and similar sources. The only advantage I see to using wrought as opposed to mild is in the historical context. Where one is trying to duplicate, as closely as possible an artifact.
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« Reply #13 on: July 20, 2012, 02:09:31 am »

As is typical, we have wandered well away from the original topic. Rather than correct the situation, I will instead point to this thread on the subject of wrought iron, wherein Mr. oftheTower suggests that the silicates in wrought iron make it much easier to forge-weld than mild steel.
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