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Discussion Starter · #1 ·
Dug up an old Garden Railways article on building lights, which covered bending brass. Re bending brass, did like the article stated...


Heated a 4" length of the brass tubing to red-hot. As I moved back-and-forth, it did not stay red-hot as it cooled down when doing further up the tube - but I would go back-and-forth where it would turn red-hot quickly. Doused it in water. Bent it by hand using a 3/4" pipe as the form. Though it bent easily, it flattened where being bent. Hmmm...try it again.

Heated the same, probably hotter this time. Let it mostly cool naturally, but did douse it in water when fairly cool. Packed the tube w/ sand this time (but may not have packed it enough). Upon bending, it did not flatten as much - but did some. I would prefer the tube to remain round throughout the bend. What did I do wrong? Would I be better off NOT bending it against the hard pipe? Is the radii too tight? Would one of those a spring benders - where the tube is slid inside a snug-fitting spring-like thing - make any difference?

Bending aluminum of the same diameter was done w/ out heating, and without deforming - but that was formed using a 1-1/2" pipe.

Thanks, tbug
 

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It could be the small bending radius as you mentioned.
 

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I have never been able to bend a tube of ANY material, (no matter how it is treated) without it flattening -- unless I use some sort of bending fixture that constrains the tube to a fixed width across the bend... e.g.: to "flatten", the material of the curvature of the tube has to go somewhere and it goes into making the tube flat and wider in the bend. By constraining the width, the flatness cannot form. I have used the spring type holders (sometimes they are really hard to get off without ruining the spring) and I have a couple of tubing benders that have curved round bottom grooves that hold the shape of the tubing while it is being forced around the curve. This stretches the material on the outside of the curve and sometimes actually compresses the material on the inside of the curve. I never had much luck with filling the tube with sand or a low melting point solid (solder or Bismuth); it is also sometimes very hard to get the tube completely emptied of the solid... sand gets embedded in the tube walls (and breaks loose later) and solder & Bismuth form an amalgam with the tube material (copper/brass/etc.) and not all of it gets removed and can then contaminate what flows through the tube.
 

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Discussion Starter · #4 ·
Thanks Semper, interesting info. All-in-all, both pieces were shaped well. I did get some clumping of sand in the brass, but it came out easily by running a wire through to loosen things, then running water through to clear it.

Here's a quick look of the bends. Aluminum bend looks out-of-round because of the angle.


tbug
 

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K&S (I think) sells a tool for bending. It probably has a name, but I can't remember. Anyway, it looks like a spring with a funnel at one end. There are various sizes for various tubes. You insert the tube & bend & the spring keeps it round. I can post pictures if I'm still not making sense.
 

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I have used the K&S springs but even better for the small radius bends you are making is the Dubro tubing bender Catalog number 785 which should be available from any good hobby shop or online.
You first anneal the tubing (air cooling is fine) then slide it in the bender to where you want the bend and close the handles to the desired angle. The bender for 1/8 od tubing will also work for 3/32 and 1/16 od.
I had to make some complex bends for my Willi live steam bash to plumb both steam motors and it worked very well.
Try it,
Tom
 

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Discussion Starter · #7 ·
Burl, I know the spring-type bender you are talking about. Don't remember the diameter, but tried bending brass some time ago using the spring-type. The brass kinked because - as I now know - the brass needs to be annealed first. Have not tried the spring-type bender since. I'll have to re-visit its use.

Tom, I did see the bender you are speaking of, but it was of for too large diameter tubing. I'll have to keep my eyes open for the appropriate size.

Thanks, tbug
 

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What size tubing are you bending? The one I use is for 1/8" dia down to 1/16" dia.
I just did a google search on Du-Bro #785 and got lots of hits. Tower Hobbies has it for $9.99 which is about $.50 less than I paid my local hobby shop.
Tom
 

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When bending brass it will work harden. You might bend it half way then reheat it to bend it the rest of the way.

Also when heating it to anneal it you don't have to have it all red hot at the same time. Once it is read hot it will be soft.
 

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Tom, thanks for the lead. Just ordered the Dubro 785 and some other stuff I can't find locally from Tower.

Larry
 
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