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Bending 1 1/2" x 1 1/2" tubing


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I had a job come into the shop today that requires that I bend two pieces of 1 1/2" .250 wall square tube into a 'U' shape with a 24" diameter. I was planning on trying the bend the same way as I did the ellipse, around a form using bending forks. I am a bit worried about the hollow tubing being crushed by the forks, but think that the .250 wall thickness will make it alright. I suppose I could try one and if it collapses I could cut another, fill it with sand and cap i and try again. Has anyone bent similar tubing to this, and do you have any tips?

Thanks,

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12" is a pretty tight radius for that dia and wall thickness tubing. The best method I've ever seen for bending tube is really straight forward but takes some serious power. This is an OLD logging and related field trick, as old as wire rope and steel pipe.

In this case slip a length of 1" steel cable through the tube, place the tube against a 12" dia. really stout tree, heavy pipe will work but mark the tubing. With the cable ends even hook it to something with lots of beans and pull it till it stops moving. VIOLA! you have your "U" bend. Do it again and you have a pair.

When I say pull it with something beanfull I mean a dozer or similar though if you have snatchblocks you can do a double and use a strong winch. Maybe a loaded 4x pickup and snatchblocks will do it but I don't know. 1 1/2" 1/4" wall is darned stout.

Oh yeah, NO heat, zero, it messes up the cable.

Frosty the Lucky.

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I managed to get the tubing bent this evening. I built a jig on a piece of scrap plate and tacked on a piece of 3/16 x 1 1/2" hot rolled flat bar into a 24"d radius. I cut 2 pieces of 1 1/2" x .250 square tube 5' long and put the first 12" into the forge. I did both pieces at the same time and it minimized my down time waiting for steel to heat. I built a bending fork out of 1 1/4" square tube and two pieces of 1 1/" pipe 5" long. The first bend went to about 22 1/2*. I took another heat on it and got to about 80*. I quenched the end up to a few inches away from the spot where the next bend was going to be. I had to do this because the tube with the bend won't go through my forge any more, so the long straight part has to go through the hole up the where the last bend ended. It took about 3 more heats to get it all the way around, and I had to straighten it up a bit as I did, as it wanted to twist a wee bit. I just used a big crescent wrench to untwist it. First pic show the last heat. Second pic shows both bends and the bending fork.

post-1700-0-39907000-1318045154_thumb.jp

post-1700-0-79811100-1318045170_thumb.jp

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12" is a pretty tight radius for that dia and wall thickness tubing. The best method I've ever seen for bending tube is really straight forward but takes some serious power. This is an OLD logging and related field trick, as old as wire rope and steel pipe.

In this case slip a length of 1" steel cable through the tube, place the tube against a 12" dia. really stout tree, heavy pipe will work but mark the tubing. With the cable ends even hook it to something with lots of beans and pull it till it stops moving. VIOLA! you have your "U" bend. Do it again and you have a pair.

When I say pull it with something beanfull I mean a dozer or similar though if you have snatchblocks you can do a double and use a strong winch. Maybe a loaded 4x pickup and snatchblocks will do it but I don't know. 1 1/2" 1/4" wall is darned stout.

Oh yeah, NO heat, zero, it messes up the cable.

Frosty the Lucky.


As some would say to Frosty the Lucky, Don't try this at home folks,

Are you recommending to give them darn trees another chance.? I would suggest adding use a mighty long cable or better still. save on potential medical bills and invest the money in a hydraulic or mechanical bender.

Oh and just to clarify 12" radius, use a 12" diameter tree, are you sure you are back yet. We love you Frosty, don't tempt fate, If a woodwise guy like you can make a mistake what chance do rookies have, we want the odds in your/our favour. I know it will work, but lets make clear the safety precautions that would be advisable.

Not getting at you Frosty, just concerned Best to Debs, I am sure she may have a little word to say about this method and its execution.
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12" is a pretty tight radius for that dia and wall thickness tubing. The best method I've ever seen for bending tube is really straight forward but takes some serious power. This is an OLD logging and related field trick, as old as wire rope and steel pipe.

In this case slip a length of 1" steel cable through the tube, place the tube against a 12" dia. really stout tree, heavy pipe will work but mark the tubing. With the cable ends even hook it to something with lots of beans and pull it till it stops moving. VIOLA! you have your "U" bend. Do it again and you have a pair.

When I say pull it with something beanfull I mean a dozer or similar though if you have snatchblocks you can do a double and use a strong winch. Maybe a loaded 4x pickup and snatchblocks will do it but I don't know. 1 1/2" 1/4" wall is darned stout.

Oh yeah, NO heat, zero, it messes up the cable.

Frosty the Lucky.


Speaking of the cable........How the heck would you pull it out of the tube?? :huh:
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Speaking of the cable........How the heck would you pull it out of the tube??

The differences in size of the tubing ID to the cable OD would help as well as a little grease on the cable before it went in.
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Okay, so a trying this particular bend with a 12" dia. tree as the mandrel might not be the smartest. So cut it down and use the stump or guy it back to a couple more trees.

I did mention pulling it with a dozer. Yes? Dozers are pretty well armored against something as small as a 12" tree.

Pulling cable to bend pipe is entirely a tensil process so the only deformation is between the cable and mandrel. Using the cable under tension and drawing it over the mandrel tree/stump will make a rounded groove so there won't be any deformation at all.

Removing the cable is no sweat, just disconnect one end from the dozer and pull it out. Dozer, remember? I don't think anyone I saw do this greased the cable but they weren't concerned with this close a diameter match either. They were bending large diameter pipe with 3/4" and not using 1" till it was 2" pipe or better.

Trees, yeah those can be sneaky. I'm not talking about messing with them unless I'm IN something made of stout steel, say a dozer of maybe if I'm making firewood an excavator with a thumb. I may have a little stubborn in me but I can learn if it's properly beaten into my head.

Frosty the Lucky.

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