Hello All,
I'm making my own canister stove, and am currently having problems with the preheating tube. I am trying to bend either 3/32" or 1/8" copper tube into a semi tight radius without it collapsing on itself. As of right now, I am heating the tube with a torch and then bending it with some pliers. This isn't working so good and it collapses on even moderate attempts. All the wire and tube benders I found so far are too big..Any clever suggestions without spending much money? Thanks! Mark

Have you tried the spring type? It is basically a spring you insert the tube into and then bend it. I don't know if they make one that small but you may be able to find a random spring that fits.

Many hardware stores have a drawer of small, long springs. It is usually located with the nuts and bolts, in the small drawers you pull out.

They do make a small tubing bender. It is located with the copper roll in plumbing, but agin, I am not sure how small.

Greg

Try threading a cable through the tube before bending.

Hi Mark,

With small tubes I most all of my bending of small diameter pre-heat tubes cold and use my fingers, it takes some practice. If I need to bend a tight radius I make a jig. Doing the bending while hot the tube is often too soft.

Filling with sand sometimes works.

Tony

Hey guys,
All great suggestions! I will try those first thing tommorow. Cheers! Mark

Filling with sand sometimes works.

Yep, this was my technique years ago - and still is. Works very well. Tap the tube to get the reminisce of sand out after bending.

Edited by Steve_Evans on 01/28/2009 00:41:20 MST.

the copper tubing that i've used for preheat tubes was very hard and needed to be annealled before i could bend it. to do this, heat the copper red hot and let it cool down. after annealling i could bend very tight radii using just my fingers. it's a lot easier to polish the copper (after annealling) before bending it.
Daren.....

The Imperial Eastman 368-FH tubing bender is great for this. I used to sell auto parts and sold dozens of this tool over they years. I used to demo it by bending a steel brake line into an overhand knot.

http://www.restockit.com/1-4-5-16-3-8-Imp-Triple-Header-Bend-(389-368-FH).html?source=froogle&Bvar5=100F1&Bvar6=100F1&Bvar7=100F1

If you have a one-off project requiring a fancy tool, rent it.

Hi Mark

There are two secrets to bending tubing without it collapsing.

The first one is to fill it up with sand or springs or whatever, so it can't collapse on itself. This works, but can be a shade tricky with small tubing.

The second way can be understood if you watch what happens when you bend a tube and it collapses. You will see that as it starts to collapse the tube first starts to spread outwards. Bend a straw and you will see this very clearly.
Now take a look at the tube benders mentioned in the previous posting. You will see that they feature a semi-circular groove right around the bend. This groove matches the size of the tube. When you press the tube into this groove it cannot collapse outwards: there is no room at the sides. If it can't collapse outwards it can't flatten (up to a point of course!).

So what you need to do is to make (or buy) a bender with a groove matched to your tubing. If you have access to a lathe this is easy. If not - more difficult. Try mounting a round bit of aluminium rod in a drill press and using a file from the side as it spins. Make the groove a full semi-circle: nothing less.

Using this technique I can not only bend SS tubing into suitable tight curves for a preheat tube, I can also bend Easton tent poles into circles of about 1.5' diameter (several passes, using rollers). I kid you not!

Cheers

先ず始めに、銅パイプを焼き戻すと柔らかくなり加工出来ます。
少し曲げると、直ぐに、加工硬化の現象が起きます。
脆く折れやすくなります。
再び焼き戻しします。

焼き戻す：それは、ガスの火で炙るだけです。簡単です。
私は、何度も繰り返して、折り曲げ加工をしながら
ストーブの実験を繰り返しています。
３回ぐらいは、可能です！

Yukio, above, kindly points out that:

"
To start first, to soften and restore processing can burn the copper pipe.
And slightly bent, soon, the phenomenon of work hardening occurs.
Brittle broken easier.
The re-tempering.

Grilled back: it is simply roasted in the fire of gas. Is easy.
I have repeated many times while the bending
We repeated the experiment the stove.
About three times is possible!

Edited by Lynxrat on 08/23/2009 09:01:28 MDT.

There is a youtube video on this. You preheat the tube with a flame and while hot wrap it around a pipe of the diameter you need. The "template" pipe is clamped in a vise.

I use this method to bend 1/4 ... 3/8 copper pipes into ~1.5 diameter circles for plumbing.