Bending Copper Tubing

[Mark Hulette]

I'm working on a speaker stand design for my home theater system and after looking across the WWW I've found a couple of interesting ideas to incorporate into the stands and it includes copper tubing (1/2").

Here's the question:

What's the best method to bend this media (not more than about 45 deg)without crimping it. I'd like to keep the tube from kinking. Make sense?

I'd post pics but this is still in R&D...

Thanks!

[John Hixon]

Some kind of tubing bender. Pretty much anything else will kink the tubing.

There are two types that I know of...

One with handles that wrap the tubing around a form.

One shaped like a spring that fits around the tubing and allows bending, if not to sharp a bend, and more or less free form. The spring type come in different sizes, maybe a kit with several sizes.

Either available pretty much everywhere, spring is probably cheaper.

[David G Baker]

Mark,
If you are bending tubing, John's suggestion will do the trick but if you are going to use copper pipe you will need a different method. When I was a kid I worked for the Southern Pacific Railroad as a pipe fitter/sheet metal apprentice. I watched the old journeymen pipe fitters bend 1 inch copper pipe. The soldered a cap on one end of the pipe and filled and tamped moist black sand into the pipe until they couldn't get any more into the pipe. They then placed a non soldered cap on the other end of the pipe so steam generated by the heat wouldn't blow out the walls of the pipe. They would bend a brazing rod into the shape of the bend they wanted. The pipe was then placed in a vise with a wet grease rag wrapped around it to keep the vise from marking the pipe. A torch flame was applied to areas where they wanted the bend to start. The pipe was heated to cherry red in small areas and the bend was started. They would bend the pipe a little at a time, cool the pipe with a wet rag and when the pipe cooled they would re0heat the pipe a little further away from the first bend. They would keep this up until they ended up with the bends they needed. this process would take hours, depending on the type of bend. I saw them bend thin wall copper pipe into a complete circle.
The purpose of the sand is to prevent the crimping and support the pipe internal walls. I do not recall why the sand was the black sand but it could be that the sand compressed better than regular sand.

[Jeffrey Makiel]

Two ways...
1. Bending tool shown below. An inexpensive one can be found at http://grizzly.com/products/Pipe-Bender/H2925
2. Use a bending spring. It's just a spring that goes over the tube to prevent kinking while hand forming. Lowes or Home Depot may have one for 1/2" tubing. They are more commonly available for 3/8" tubing.

It helps to use soft copper tubing (commonly used in air condition refrigeration lines 3/8" or 5/8"). It has been annealed and therefore easier to bend versus standard type L or M tubing found at home centers.

-Jeff :)

[Matt Meiser]

There's softer copper tubing sold in rolls meant to be bent. But it seems like that wouldn't hold up well in your use. The harder pipe sold in 10' sticks should be able to be bent using a tubing bender like fabrication shops--the same kind of bender used to bend tubing for things like motorcycle frames or roll cages. However, there is a difference between "tubing" and "pipe". Tubing is measured on the OD while pipe is measured on the ID. To get smooth bends, you need perfectly fitting dies. Dies for 1/2" pipe won't work well on 1/2" tube because they have different OD's.

You might look around to see if you can find a welding or fabrication shop that could bend it for you for a couple bucks. But it might be hard to find someone with the right sized dies.

Depending on how much you want to spend, I can think of one potential solution that could be done for <$100. Harbor Freight sells what is called a universal bender. The bench mount version goes on sale for about $70. There is a seller that sells dies on Ebay that fit these universal benders for bending tube (typically steel) But since you are bending relatively thin and relatively soft copper, I think you could duplicate his idea in a hard wood like Maple on a lathe.

[Don Abele]

You mean bending copper like this?

98739

This is the chilling unit I use for when I homebrew beer. It's about two feet tall and 12" wide. I made it about 15 years ago from 25 feet for 1/2" FLEXIBLE copper that I got at a plumbing store (the borgs didn't carry 1/2").

I tried to bend type M (thin walled) copper and it just kinked no matter what I tried.

I moved up to type L (medium walled) copper. It took A LOT of effort to bend it and went VERY slowly. The bends were also not very smooth.

I never even tried type K (thick walled) copper. I don't imagine you could bend it though.

I bent this using the spring that has been talked about and used very firm, steady pressure as I wrapped it around the form (I used one of my 5 gallon soda kegs). It was not easy, but it turned out great and works fantastic.

Be well,

Doc

[harry strasil]

if you want to bend the 10 ft stuff, heat the area you want to bend and quench(cool) in water quickly, it anneals(softens) it, when done heat again and let air cool (hardens) it. I bent all kinds of pipe and tubing in the blacksmith shop, I just used the right sized cable sheave (pulley) as a bending die. You can make a die easy enough by sandwiching the right sized circle of plywood with a circle on each side that is bigger.

[Eric DeSilva]

You can anneal any copper to make it easier to bend--heat it up with a torch cherry red and then let it cool. As soon as you work it by bending, however, it hardens and undoes the annealing. So, if you are doing radical bends, you may need to anneal it several times. Once worked, the copper will be hardened again.

At least, this is the way metal worked when I was pretending to be a silversmith.

I prefer the tubing benders, not the springs. Too bad you aren't around DC, I've got a tube bending rig that you could borrow. Unfortunately, the set weighs like 150 lbs.

[Mike Cutler]

Mark

I've bent and installed miles of tubing and pipe over the years.

First things first.

Are you using copper tubing, or copper pipe? Copper tubing is sized on OD. and copper pipe is sized to ID, based on schedule. The tools to bend pipe and tubing are not interchangable. The bender in Jeff's post looks correct for pipe, but you would have to ensure it isn't a conduit, or an EMT bender. Yet another size of pipe for a different application

Tubing and pipe both adhere to an ASTM standard. For the strength of your project, is there a recommended ASTM value?

What are radius values you need to bend to? The minimum bend radius can be dependent on the material selected. Pipe radius is referred to inches of bend radius. Tubing is referred to in fractional and multiples of the tubing diameter.

It's sounds like alot of hassle, but it's really not. It's actually pretty easy.

As for a bender. One of the easiest thing to do, if you have multiple lengths, bent to the same shape, is to make a bending form out of plywood. Very easy to do, very accurate.
With a traditional bender you have to compensate for the diameter of the material and the effect it will have on a left, versus right hand bend.

Yep. I do this for a living.;)

[Mark Hulette]

Hey guys~ WOW!!!! :eek:

So much info!! Thanks for all the suggestions.... whew.

The idea is to use the pipe/tube/copper stuff as the vertical upright that supports the speaker. That conglomeration is supported by a wooden base. In my estimation, 1/2" should be plenty strong as these speakers aren't that big.

I have done a bit of soldering on plumbing items and didn't really want to use heat if it's going to change the color or patina of the copper. I'd like it to stay "coppery" if possible. Is that understandable?

What about using a spring INSIDE the tube that's in the bender (handheld HF-type)?

Boy, I really appreciate all the expertise here in the Creek!! Thanks again!

[Dick Strauss]

Mark,
When they make brass instruments like trombones and trumpets, they fill the pipe/tubing with water and freeze it. Then they bend the pipe before the ice thaws so that the ice suppports the pipe from within and keeps it from kinking. They bend the copper tubing with no heat applied. Once you have it in shape, you can harden it as necessary. You can also clean up the oxidation with some 0000 steel wool or flux. Bear in mind that you'll want to coat the pipe/tubing with lacquer to keep it looking shiny.

Make sure you show us the project once you get it finished. Also, make sure you take pics as you go...


Good luck,
Dick

[Lu Seli]

Hi Mark:

I have had good luck using tube bending springs as follows > I use an inside spring to make tight turns and an outside spring to make gentle curves.

Ciao

[Mark Hulette]

Mark,
When they make brass instruments like trombones and trumpets, they fill the pipe/tubing with water and freeze it. Then they bend the pipe before the ice thaws so that the ice suppports the pipe from within and keeps it from kinking. They bend the copper tubing with no heat applied. Once you have it in shape, you can harden it as necessary. You can also clean up the oxidation with some 0000 steel wool or flux. Bear in mind that you'll want to coat the pipe/tubing with lacquer to keep it looking shiny.

Make sure you show us the project once you get it finished. Also, make sure you take pics as you go...


Good luck,
Dick

Dick- Interesting suggestion since I play trombone! Speaking of instruments, I'd like to seal the copper with lacquer as is done with brass instruments. IS there any special product for this or can I use Deft?

This project is still down the honey do list (actually its on my list and we all know whose list gets priority!) so I'll be sure to take some pics as I go... if I get to it! :>)

[Joe Petersen]

Has been stated, but seems to have gotten buried along the way.
Just fill the tube with plain sand, tape the ends up and bend around a makeshift die to proper angle. No heat needed on half inch.

[glenn bradley]

For artistic, free-form curves, these work well.

[Dick Strauss]

Mark,
As far as the finish goes, try searching for "brass lacquer" to get some good ideas.

I think ice does a better job of filling all spaces evenly. The ice will crack as you bend the pipe but it will only separate on the outside of the curve (where you don't need as much support).

I'm not an expert but have seen the complete process...

[Rich Engelhardt]

Hello,
Have you considered using a solid rod instead of tubing?

[Russ Filtz]

Second the sand fill method. That's how I've always heard to bend pipe/tube without kinking. May require a fairly good taping up at the ends or you may just squeeze out the sand and negate the support it provides. Most likely not though.

[Ross Ellis]

If you can't find a proper tubing bender and decide to use a pipe bender, I also recommend going with sand. Tape the ends. Copper is pretty soft and should bend quite easy. Also, if you don't have a lot of experience bending and want the stands to match, do the bends in the tubing at the same time. By this I mean do the first bend on each piece, match the bends up, then move to the next bend. Don't make a bunch of bends in one stand, then when finished start on the other. Use tape or marker around the tubing to see where you start and finish each bend. Once you start making more than a single bend, it can become difficult to match pieces up. I hope this makes sense.

[Ted Calver]

Back when I was in scouts we made pack frames from aluminum tubing by filling the tubes with sand taping the ends and using a clampable 2 piece bending jig made of wood in the shape of the frame ribs. It worked great and gave us consistent shape with no distortion--prolly work on copper too.