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Old 07-09-2016, 14:33   #16
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Re: Bending 31L Stainless tube

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Originally Posted by Cheechako View Post
Yeah, I've bought a few machines for aerospace work. It's all mandrel bending. We even did some .025 wall titanium bends down to a 1.5 D radius! ... in diameters like 3" and bigger...
The bronze ball mandrel supports the material from wrinkling and a wiper die wipes the tube around a bend block. The ball mandrels must be in precisely the right place throughout the bend.
I've not seen a system that pulls the ball thru after bending to remove wrinkles. In sheet metal, the material has to go somewhere, it either changes shape or gets thicker. Pulling a ball thru would create stresses and change the shape I would think, but there is a lot of new stuff so maybe so....
Commercial things are made somehow. It may be cheaper to buy davits. I think that was the OP.
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Old 07-09-2016, 14:42   #17
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Re: Bending 316L Stainless tube

At 10-12 times radius to the diameter you don't need any mandrel, sand or etc in most bends. Not even close to a problem. If you can find a conduit bender that's close to the right tube diameter that would work. Any difference in die vs tubing diameter may result in ovalizing a bit. If close you could put stretchable tape on the tube in the area of the bend, that will protect from scratching too.
But better yet, find your local marine railmaker, and ask about them bending what you need, create a relationship so can get them to electropolish after you weld .
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Old 07-09-2016, 15:01   #18
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Re: Bending 316L Stainless tube

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At 10-12 times radius to the diameter you don't need any mandrel, sand or etc in most bends. Not even close to a problem. If you can find a conduit bender that's close to the right tube diameter that would work. Any difference in die vs tubing diameter may result in ovalizing a bit. If close you could put stretchable tape on the tube in the area of the bend, that will protect from scratching too.
But better yet, find your local marine railmaker, and ask about them bending what you need, create a relationship so can get them to electropolish after you weld .
Even better though - get them to pull the bends for you.
I did that for my panel arch. Bought the tube, cut to over-length, taped start and finish of each bend, noted angle needed etc. Paid with a slab (case of beer for those northern hemisphere folk) Simple.
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Old 07-09-2016, 15:02   #19
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Re: Bending 316L Stainless tube

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Even better though - get them to pull the bends for you.
I did that for my panel arch. Bought the tube, cut to over-length, taped start and finish of each bend, noted angle needed etc. Paid with a slab (case of beer for those northern hemisphere folk) Simple.
Yes.... I think that's what I said!
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Old 07-09-2016, 23:53   #20
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Re: Bending 31L Stainless tube

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Sounds crazy, but filling it with sand before bending may help, plug the ends of course.
this is the best answer if you don't have access to a mandrel bender. you can also use water but it's much more difficult than sand.
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