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How to Bend Copper Pipe and Tubing without Crushing It

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I recently made a copper tubing coil to use in a solar-powered water-boiler and learned the right way and the wrong way to bend copper tubing.  The tubing is easy to bend when making large-radius curves, but is likely to kink or crush when trying to make smaller-radius bends.  I learned that I could avoid those problems by filling the tube with salt before bending.

Here's what I used.
  • .25 inch Copper pipe.  5 feet long
  • 1/4 cup of Salt.  (Fine, dry Sand would also work)
  • Tape
  • Funnel (or makeshift funnel)
  • Vice
  • Hammer
  • Hard Cylindrical Objects of various diameters.  I used a 3" diameter steel pipe and a 1.5" diameter socket-wrench socket.

 
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Step 1: Fill it with Salt

  1. Your tubing probably came as a coil, so straighten it out to begin.  Use a flat surface like a table and roll the coil while holding one end on the table.
  2. Stand the tube upright and use some tape to cover the bottom hole.
  3. Use a funnel or other tool to pour the salt into the tube.  Fill it all the way to the top.
  4. Help the salt settle by tapping the tube on the ground.
  5. Refill with salt until it can't settle any more.
  6. Cover the top hole with tape.
Now you're ready to bend.

Step 2: Bend using a Cylindrical Object

  1. Begin by bending your tubing into a much bigger circle than you want to end up with.  
  2. Clamp your cylindrical object in the vice and, by hand, gently wrap the big coils down to coil around the cilinder.  Sometimes a twisting motion can be useful, turning one end of your coil clockwise and the other counter-clockwise.
  3. Tap the tubing with a hammer (while it's on your cylinder) to help it reach an oval-shaped cross-section.  This lets it stay happy even when making tight coils.
  4. Continue the process with smaller and smaller cylinders until you are at the size you desire.
Take the tape off the ends and shake out all the salt!
You're done!

For more advice on bending tubing, check out this article.

If you're curious about the Solar Parabolic Water Heater, check out the instructable.
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DanYHKim2 years ago
I like this idea. I'm guessing, but I would think that salt would have the added benefit of not scratching the interior of the copper tube, which I imagine sand might do.
Aach! Hit submit too early!
Would a wooden mallet or wood-faced hammer be a good choice for not marring the copper?
GrfxGawd DanYHKim9 months ago
Possibly, but rubber or polymer might prove more durable or even more effective.
glorybe11 months ago
If you have access to a metal lathe you would be astounded at how easily one can wrap the tube around a pipe. The lathe is turned manually. No power is used at all. A small hook shaped piece keeps the beginning of the wrap in place. I had reason to make many of these coils in stainless steel and it was a lark. The only error is if you choose too small a pipe for a form the bend radius can get too small and then it will be a war of sorts.
glorybe11 months ago
Tubing for musical instruments traditionally was bent by either being filled with lead or frozen soapy water. The companies involved do not release the type of dish soap or the amount used in proportion to the water in the mix.
The important part is mostly that the mixture be well frozen.
These days the best method is to have a die built that holds the pipe and hydraulic pressure is used to force the tube to perfectly fill the void.
gablafy11 months ago
Always always use salt. The salt dissolves in water, the sand does not dissolve in water. The pressurized air can not completely clean the ducts if using sand. All engineering manuals clearly say that the duct is obstructed by time.
Markymoo11 months ago
I quite easily coiled 8mm copper tube around a 45mm mandrel.....
First thing was to wind 6metres of 8mm round a 6" paint can by hand and then round a 4" stainless steel sugar can, just smoothing it round as you go..... Relatively easy.
Then... Fill with water and put in the freezer over night!
In the morning get your 45mm mandrel/pipe or whatever slip it inside your 4" coil and literally roll the pipe and smooth as you go. I got a perfect coil over a foot long, and cold hands..... I was surprised how good it came out. No kinks or bends and very minimal, practically no flattening. Well chuffed!!
rio45801 year ago
sand works just as good
3366carlos1 year ago
very nice.
Please everyone, call it what it is. By this I mean there is such a thing as copper tubing & copper pipe. To entirely different things.
Ok, that's out of the way, I've never used salt before to bend tubing or pipe. As salt can get extremely hard in either, especially if your using heat to bend. I've always used fine silica sand to bend either tubing or pipe & it's cheaper to get.
As a Duquesne mill Pipefitter we were noted for bending pipe instead of using pipe fittings. We would bend all the way up to 4" schedule 160.
But, we only used sand if we had to bend a close degree radiius.
Recently I had to make a railing for my swimning pool out of 1-1/2 aluminum tubing. This I filled with sand. I already had a jig made & also allowed for spring. I made up 2 railings, each with 1, 180 degree bend in it. In aluminum tube, bending, (Trick of the trade, heat the back of the tubing when you make the bend on aluminum. This will stop it from cracking.
(n)1 year ago
sir I want wind 12.7 mm to 16.0 mm copper pipe x 5 feet long in same manner ,,it is possible? I want to make water heater,,, .give some Idea about it sir Thank you
(n)1 year ago
sir I want wind 12.7 mm to 16.0 mm copper pipe in same manner ,,it is possible? I want to make water heater,,, .give some Idea about it sir Thank you
Bill WW1 year ago

Good job a ususal, Ben.

Today I bent 3/8 copper tubing into a 2" diameter coil, using this method, with salt. Came out pretty well, definitly would have crimped and buckled otherwise.

Others have suggested sand. Maybe that would be OK for larger tubing, but salt is cheap and uniform in size. Most importantly, whatever you use (salt, sand) will become really packed tight. I was finally able to get the salt out by dissolving it with hot water.
pekar1 year ago
There's a nice method here:
http://homedistiller.org/forum/viewtopic.php?f=46&t=11554
Using this method, I wound a perfect coil... on the second try. without salt.
also note that copper hardens the more it is bent, so straightening the tubing first isn't always the best method.
Pekar
i heard it works better with ice
Alan136262 years ago
If its copper pipe being used why not buy a bending spring,I think the smallest is 8mm and are cheap
Even better, for even tighter results, fill the tbe with low-melting-point alloy. We use a material that melts at 80 C, and then steam it out hot after forming
Brass trumpets are bent by filling the tube with soapy water, then freezing them. After forming, the water melts at room temperature.
ben.chapman (author)  lime3D2 years ago
I've heard about the ice method. Why do they use the soap?
Only saw it on an episode of "How it's Made", but I would think that is for lubrication purposes.
Trouble with ice is its crystalline, and cracks, leaving voids that tend to collapse the pipe. It might work in brass, in the very large relative curves in trumpets, but we make very fine coils
Just keep in mind that most of these low temp alloys contain a fair amount of lead and cadmium, possibly with other toxic metals, so if this is for use to heat drinking water, those alloys should be avoided. Then again, with a heat exchange system, it may not matter,
Not this one. Its largely bismuth.

Once again i find you helping with your most-excellent advice Steve !

GREAT Tip with the Low-Melt Alloy !

Im very Curious though, whats the name of the low melt alloy you use and is it easily acquirable ?!?

many many thanks too !!

;-)
We use an alloy from a company called MCP in the UK. Its an alternative to "Woods metal" which contains antimony.
thanks steve, most-highly-appreciated !!!

even-better as im in the UK !!!

but i only found a company from the website www.mcp-group.com and all the links on it are broken and dont work, would you be able to tell me if this it the place or post the correct website please please ??

once more, many thanks again !
Yeah, the website's crap. PM me and I'll try and send you the details tomorrow when I get into work.
Hi Ben, nice instructable.
I liked in particular the way your parabolic dish looks.
Is it possible to get more details/plans?

Thanks
Angelo
ben.chapman (author)  undinstructable2 years ago
I just recently finished the parabola instructable. Here it is: http://www.instructables.com/id/Building-a-Parabolic-Solar-Hot-Water-Heater-using-/
Hi Ben,
Yes would love to know how your heater came out.
Thanks,
Randy
Hi Ben ,
This is a great instructable! I too am very interested in how the parabolic reflector was constructed . It looks like ther a pieces of mirror arranged in a tile pattern inside of a parabolic dish,
Thank you
Doctorbigdaddy
It looks like he might have used polished Aluminium Tape.
Does somebody knows what will occur if I fill the tube with sand instead of salt? thanks
I have used fine sand successfully...
Sand works just as well as salt. I think the advantage of using salt is if you can't get all of it out of the tube afterwards, you can flush water through the tube and the salt will dissolve away.
I agree. I use dry sand. You must heat it during some minutes to dry. Then, use a strainer to avoid big particles.
bluemoon62 years ago
Have some tubing to make bracelets with and was wondering how to bend it..thanks for the info..will be put to use at my home...
AR10NZ2 years ago
3 metals that can be made liquid with boiling water are : Woodsmetal; Cerosafe; & Cerobend. I believe all contain lead, so NOT food grade.
AWESOME & Just what a Project of mine requires - a Fool-Proof way of bending fine-copper pipes !!!

Many many thanks ben !!!

;-)
dollywild2 years ago
so happy to see this. I have been struggling with this issue, tried ice and it did not work for what I was doing...THANKS!
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