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Author Topic: How do you bend copper?  (Read 5274 times)
Paladin
Dave Knight
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« on: January 09, 2008, 12:12:51 PM »

I need to bend 3/4" copper into 90 degree turns but don't have anything like bender or anything. I was thinking of softening it by preheating the radius before trying to work it around. Is there a better way? I'm afraid of kinking and collapsing the pipe.

-Dave
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« Reply #1 on: January 09, 2008, 12:21:19 PM »

If you have Type L or M Hard copper (ordinary house type rigid water pipe) it is not practical to try and bend it. If you have Type L or K soft copper (the kind that comes in rolls) you can make long radius bends by hand. For short radius bends you can buy a coil spring that slips over the pipe and then pulls off after you make the bend. Type K would take strong muscles to make a short bend.

If you are in fact working with hard copper you just cut the pipe and solder in elbows. Also note that hard copper is measured outside diameter and soft copper is measured inside diameter.
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makemineatwostroke
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« Reply #2 on: January 09, 2008, 12:22:45 PM »

buy you some 45s or 90 degree bends and use solder trying to bend 3/4 in copper you will have a very long 90 degree bend and heat is not a good idea to bend copper fwiw and good luck
« Last Edit: January 09, 2008, 05:04:09 PM by makemineatwostroke » Logged
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« Reply #3 on: January 09, 2008, 12:35:53 PM »

Thanks guys, I should have specified that it's rigid copper, 3/4" o.d
I'm trying to duplicate the coolant lines that are behind my drivers seat. I cut out a section so I could repair the air beam. The originals had a sweeping 90 degree curve to them. I guess the coolant doesn't care too much about a tight turn...or does it? I guess I could solder in some 45's to make a gradual 90.
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« Reply #4 on: January 09, 2008, 12:51:55 PM »

Dave

If you have the sections you cut out you may be able to put them back in.  If not you can get sweep bends to use.

Good luck

Don 4107
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« Reply #5 on: January 09, 2008, 01:40:56 PM »

There are tubing benders available on the E place for bending copper tubing. Since you're trying to bend 3/4" tube you might TRY a conduit bender.  Bearing in mind that the stationary part of the tubing might dent if you apply too much force.  The other method that might work is sand bending.  Not sure of the type of silicone sand they used but the tubing is filled and tightly capped...then bent very slowly. the effect is no sharp bends.

Regardless of the method I would certainly anneal the tubing after the bend to help keep it from work hardening.

Bob
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« Reply #6 on: January 09, 2008, 01:47:41 PM »

Use solder elbows. Don't try to bend it.

FYI, those tubes behind the driver are 5/8", not 3/4". You won't be able to find that diameter, but with a bit of effort, you can make the 3/4" fit over the original and fill the joint with solder. It's a bit sloppy, but it will fill with care.

Another idea is to use rubber heater hose with clamps and leave an access in the floor to get to it later on. I wish I had done this on mine because I'd really like to put in a driver heater unit off the bus heat, but didn't think of it soon enough.

craig
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Craig Shepard
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« Reply #7 on: January 09, 2008, 02:06:29 PM »

Mine must be a weird oddity or else I'm not doing it right since my 3/4" unions fit and thus the 3/4" pipe will fit the other end....if I can get the bend or get angles soldered in.

I'll have to see how this all works out in the end.
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« Reply #8 on: January 09, 2008, 02:18:37 PM »

If you have to bend it, fill it with sand. This will prevent kinks.
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« Reply #9 on: January 09, 2008, 02:36:23 PM »

As often, I seem to have different experiences than many others here do.  I see absolutely no reason that heating your hard copper and then bending it won't work.  In fact I do it all the time.

The deal with "hard" copper is that it's been hardened by one of a few means available at the factory (work hardening, thermal hardening, etc).  If you heat it to a soft red glow, it will become annealed=soft.  There's nothing different about soft copper vs hard copper as far as alloy, it's all pure copper.
In fact, heating "hard" copper in this fashion will likely result in copper even softer than the "soft" coiled stuff you can buy at the depot.

You'd of course want to heat a bit more area than you're going to bend, not try to bend it in a tighter radius than any tubing of that diameter will allow, etc.  Filling it with sand is a great way to avoid kinks as Green Hornet mentioned, and benders do wonders too.  When you're done the pressure rating will be slightly less than in a non-annealed state, and it will be oxidized like crazy both inside and out (which won't hurt a thing)

Bottom line, try it, if you like it, there you go!!!  Oh...Yeah... Coolant, like anything in a pipe, likes sweeping turns much better than tight 90's.  Less restriction.  Not that it matters but tight turns all add up and eventually enough of them will definitely reduce flow.
« Last Edit: January 09, 2008, 02:39:01 PM by boogiethecat » Logged

1962 Crown
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« Reply #10 on: January 09, 2008, 04:35:57 PM »

Boogie,

A very good post, the best of the bunch.

However, I don't agree about annealing copper by heating it to a soft red. This actually will harden it unless it is quenched in water. I do this all the time with copper spark plug gaskets and it makes them soft as butter.

The method you described works with iron and steel but not Cu or Al.

It won't really matter whether it is hard or soft for the use Dave explains. Pressures in the coolant lines probably never exceed 15-20psi so he has no pressure problems either.
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« Reply #11 on: January 09, 2008, 04:54:45 PM »

although fluids do like nice curves rather than 90's in most applications it does not matter much....

if your the type that needs to get every oz. of flud dynamic/hydraulic performance....and dont want to do a bend.....you can always use 2 45's

persoanlly I would go with a soldered joint rather than a bend.....I like the look, more comactness of plumbing and the ability to replace sections, if I am using copper

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« Reply #12 on: January 09, 2008, 05:38:39 PM »

Gus, I think if you actually try quenching copper in water or not, it won't matter either way.  Quenching in water will help you not burn yourself though!!.   I'm not writing this from my "armchair"... like you with your plug gaskets, I soften copper tubing all the time this way, and water isn't part of the process.

Technically, annealing is performed by heating the copper until it is glowing for a few moments and then allowing it to cool slowly
Simplified, the atoms of copper get hot enough to allow crystal defects in the metal to reorganize into a form that no longer has stresses associated with it, thus softening the metal.
If you cool it quickly (ie by quenching) you may create and "freeze" new crystal defects in place and actually make it harder.  This is, in fact, one of the methods used to make copper hard, steel too.

The reason you can get away with softening copper by heating and then quenching in water is straightforward- the water boils at the interface and turns to steam, the steam thus generated insulates the copper from the water and because of that, the water cannot transfer heat away from the copper fast enough to have the process actually act as a "quench".  Water is not a part of the annealing equation because it can't act to cool fast enough.

That's why, for example, there's this stuff called "oil hardening steel", if you were to heat it and then quench it in oil it would get hard.  But if you tried to do the same using water instead it would get soft for the same reason that water quenching copper doesn't do anything.  It vaporizes to steam and then is incapable of removing heat fast enough, whereas oil doesn't vaporize nearly as easily and will take the heat away fast enough to cause hardening.

If you want to bone up on the subject a bit, take a quick and dirty glance at the process by looking up "heat treatment" and "annealing" in wikipedia. You'lll probably learn more about metallurgy than you want to, but it's got some accurate explanations.

I'll stick with "heat it to red and let it cool slowly"...

Cheers
Gary (with way too much time on his hands today)
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1962 Crown
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« Reply #13 on: January 09, 2008, 06:13:05 PM »

Gary,

Maybe this is all as you say but not in agreement with my actual experience. When I quench copper plug gaskets in water they are immediately cool to the touch so the water obviously transfers the heat and very rapidly. I anneal some Al alloy aircraft rivets the same way.

There is steam at the instant they touch the water but only for an instant, then the water is obviously removing the heat since it completely surrounds the gaskets.

Next time I need some soft gaskets I'm going to try your method to see if there is any difference. I anneal new gaskets also because most are very hard, probably work hardened from being rolled out and punched out of copper sheeting.

Heating and allowing to cool slowly, sometimes in an oven, is the method of hardening non-ferrous metals as I understand it and this is also the method for annealing ferrous metals?

I thought oil is used for hardening steel because it results in less corrosion than water and it results in more depth uniformity for the hardening. I'm no metallurgist but this is from research and actual experience.

I'm house bound with a horrendous cold so I have too much time on my hands also!
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« Reply #14 on: January 09, 2008, 07:26:32 PM »

Hello   FYI    you can get long sweep elbows and street ells in any size especially  3/4 cu..  Grainger or fastenal are two suppliers.  I am sure your local plumbing house can get whatever you need.   
     WE are using two inch to replumb the radiators for an L10engine swap so everything is in the 2" range.
         happy bussin     Mike
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« Reply #15 on: January 09, 2008, 10:48:55 PM »

About 35 years ago, i had a job in heat treating for about one month.  I didn't learn much then, and I've forgotten most of that.  As I remember it we tried to reach specific measurable hardness by adjusting the temperature of the furnace and the salt bath that was used for cooling.  I was told it was molten salt and was in the area of 700 degrees F.  The product was then cooled again in water, but I think that was just so it could be handled.  I was under the impression the using water as the primary cooling agent was too extreme a temperature change and that oil would be a better choice.  All that speculated upon, your purpose does not require any strict parameters.  I would guess that doing it the easiest way that completes the circuit would be adequate.
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« Reply #16 on: January 10, 2008, 04:58:18 AM »

This has been an interesting discussion on mettalurgy and further proof that you can do anything with enough time and money. I stand by my original post 'it is not practical to bend rigid copper pipe'.
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« Reply #17 on: January 10, 2008, 06:22:13 AM »

This has been an interesting discussion on mettalurgy and further proof that you can do anything with enough time and money. I stand by my original post 'it is not practical to bend rigid copper pipe'.

That's why they make solderable fittings  Wink
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Craig Shepard
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« Reply #18 on: January 10, 2008, 06:41:10 AM »

How well would rigid copper bend using one of the hydraulic tail pipe benders at a muffler shop?  I had some tail pipe bent for my generator installation.  I think several feet of 1Ĺ" pipe, two bends, and a couple expansions cost around $15-20.  This was at a smaller 'good ol' boy' type of shop.  I'm not sure how the copper would handle the bend, but perhaps filling it with sand first and then having it bent on one of those machines would work.

David
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« Reply #19 on: January 10, 2008, 08:59:42 AM »

Dave, the rigid copper won't bend at all in any bending machine or tube bender unless is annealed first.  Then it would bend fine in an exhaust tubing bender, as long as it is the right diameter for the tooling you'd be using.  If you try to bend hard copper as-is, it will break.  That's real point of this thread and the main reason annealing is necessary... "soft" isn't synonymous  with "easy"... "soft" in this context means that it's not so hard that bending it will break it...
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« Reply #20 on: January 15, 2008, 02:25:44 PM »

Ok, for anyone who cares.  I bent my 3/4" copper doing sort of a blend of ideas from here.

It's pretty rigid but did come coiled in a large coil so that's a good thing, odd though because it is 3/4 o.d. I filled the copper with sand and taped off both ends after tamping the sand down semi tightly. I looked around for something to bend it around and found that a curve on my wrought iron railing matched the desired curve fairly closely. I duct taped one end of the pipe along the curvature to hold it steady and then I fired up the little torch with propane, was going to use mapp but decided to try propane first, anyway I heated the section I wanted to bend including about 4" either way and slowly worked it into my bend. It did begin kinking ever so slightly so I just used a pair of slip joint pliers and worked it back into round. I think I got a little to hurried is why it began to kink a little. After I was done I blew out and rinsed the sand from the pipe.
Overall I think it'll work for the job. I got a sweeping 90 degree bend with no restrictions and no kinks.

Now I just gotta slip the pipes into the unions and I should be good to go.......unless I decide to do as Craig mentioned and add provisions for a loop in there for another heater inline.  Might need to add another pump for that though, worried about loss of flow.

-Dave   
« Last Edit: January 15, 2008, 02:28:48 PM by Paladin » Logged

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« Reply #21 on: January 15, 2008, 03:13:27 PM »

If it came in a large coil, it is not rigid copper pipe.  It's good that it worked out, and there was no reason to use rigid pipe anyway. 
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« Reply #22 on: January 15, 2008, 09:24:21 PM »

Lin is right. If it came in a coil it is soft copper and how hard it is to bend depends on the grade which is primarily the wall thickness. You may have got type K which is heavy wall and common because it is used for underground water service lines.
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Paladin
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« Reply #23 on: January 15, 2008, 09:33:11 PM »

Whatever it is it fits and I consider myself lucky to have found it, especially locally. Most of the people I talked to around here just shrugged when I asked them and had no clue. I was a bit worried I wouldn't find the right size although 3/4" isn't exactly hard to find, just 3/4" o.d.
Cost was about $5.50 per foot, a bit expensive but then copper is up.
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« Reply #24 on: January 16, 2008, 07:28:32 AM »

Now I just gotta slip the pipes into the unions and I should be good to go.......unless I decide to do as Craig mentioned and add provisions for a loop in there for another heater inline.  Might need to add another pump for that though, worried about loss of flow.


Put it in series with your defroster lines. Just tap into the supply line and run a loop out to behind the seat so you can add a small heater for the driver area and tie it back in where you cut it. No pump needed. Of course this will only work on when driving, unless you modify it and tie your house system into this line also. I was going to do that but decided against it when I looked for the lines in the tunnel area and decided I didn't want to try soldering in that cramped area with all the other mechanicals and such.
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Craig Shepard
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