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bending tube by a torch and quench


stumpy

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Hello all, I'm new to this community.
I'm looking for some advice on how to, or if possible, bend square tubing with a torch and quenching it alone, or having to also apply force, like a form. I have been told this very effective and has zero distortion. I like to build decorative gates, and sending it out to have it rolled slows every thing down and cost too much. Thanks for any feed back.

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The distortion may not be very noticeable, depending upon the radius of the bend, but it will certainly be there. There is no way for it to not distort. Take your section of tube, pipe flat bar, angle or whatever. draw a line lengthwise through the center. Whatever is on the outside of the centerline had to get longer (and thinner) during the bending. Whatever is inside the center line had to get shorter (and thicker)during the bending. This is distortion.
One way to clearly see this is to take a flat bar, say 3/8" by 2", heat it to forgeing heat, and hammer along just one side of the bar. The more you hammer it and the thinner it gets, the more it will bend in the other direction. I use this method alone to make curved strap hinges, even though I have other ways to edge bend flat bar, because it is easy and controllable and customers want "the hammered look" sometimes.
Back to your question, yes you can bend tube that way. It will be slow, expensive, and with a learning curve.
To understand what you are doing, the way heat shrinking works is;
Upon being heated intensely, the steel will expand, in all directions, but mostly in thickness.
Upon cooling the steel will contract less in thickness and more lateraly, with the end result being twofold, 1. the heated spot will be thicker. 2. the surrounding metal will be pulled toward the heated spot.
The result of the heating will be essentialy the same whether quenched or not. The quenching allows the work to proceed faster.
I think that for your purposes rolling would be preferable.

Actualy, all that being said, if you really want to avoid the rolling, try the method mentioned by Francis, above.

Edited by arftist
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