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bend radius 2 x 2" ERW square tubing

depends on the machine, and the wall thickness, and the material, but it should be.
I use a 3 roll angle bending machine to do it, and have had success. The dies need to support the material on the sides. And there will be some deformation- it will no longer be a square when its done, but a trapazoid. The metal has to go somewhere, and you are asking the inner diameter to shrink, and the outer diameter to stretch.
My curvatricci takes multiple passes to do this. I mostly roll 304 stainless this way, which is also ERW, but harder to bend.
 
Ries,
It will be .063 ERW and I have a three roll bender. I do need to make up the dies.
I expect it to take multiple passes. How much clearance should I allow on the dies?
I just need to roll half circles.

Thanks
Michael
 
If you are going to make dies, I would make a set of stackable multipurpose dies, rather than specific dies for this size tube. Its actually less work, as they are all just discs, and it will be usable for many things in the future. Clearance should be 1/32" or so, up to 1/16". You want the tubing to slide easily, but not have much slop.
It will grow as it gets rolled, and fit tighter. Which is why most angle rolls have at least 2 rolls driven, and often have knurled dies.
You need a larger, say, 6" diameter inner and outer die, which is perhaps 1/2" to 3/4" thick, then a series of smaller diameter, maybe 3", plain or knurled dies in 1/4" increments, and some 1/8" and 1/16" spacers as well. Then you just stack em up to fit your part.
Of course, the diameter of your roll shafts will affect the dies.
Mine are around 1 1/4" diameter, with a key, so my dies all have interior keyways cut in the ID.

if you google any of the angle roll dealers, they show dies.
 
Ries,
Thanks for another great post, as usual, full of good information and on point.
I was planning to make sectional dies and I do have some stuff to start with but needed some extra info.
Does the knurling impart any marks onto the workpiece?

Michael
 
yes, knurled dies will often leave an impression.
it depends on how hard they are working.
If you are bending a relatively large radius in a material that doesnt work harden too much, it may not even be visible.
On the other hand, if you are bending 1/2"x 4" 304 SS the hard way, the knurl marks can be deep enough you need to grind them off.

there is always the trade off between cost and quality- the very best angle/section rolls, like the Roundo's, from Sweden, have an individual hydraulic motor for each of the three rolls, and a hydraulic ram that raises and lowers the center roll. With that much rotational force, and that much ability to fine tune the pinch, you can minimize knurl marks.
With a single powered roll, or the lower two rolls chain driven, you get more chance of rotational slippage, requireing more downforce from the third roll, and, thus, more marking.

I have a set of smooth spacers, but find that with some bends, they slip. Usually on large stuff, and on bending flat bar the hard way. You wouldnt need knurls for something simple like 1" solid round, or for aluminum tubing, say. Most pipe and tubing dies are not knurled.

Knurling on dies is just a straight knurl.
 
A 24" radius on 2" tube should be easy--at least as far as strain on the machine is concerned--that's a very large
radius for that size. I'd be more concerned about distortion if you plan to use .065" wall tube. That's pretty thin and
it's going to have a lot more tendency to buckle and collapse as you roll it. If you can step up the thickness of the
tube a bit you'll have better results. Best bet is to experiment with some different thicknesses and figure out which
gives you the best overall results. I am assuming that this is a structural/fabrication part so it probably doesn't have
to be perfect but you want it to look as good as possible...
 
Honestly if after 180 degrees i would not roll it that tight, i would get it mandril bent if you can find some one with the dies and a big machine, the results will be a lot better, faster and less effort, that said i do kinda also agree with Ries, your well into rollable at that radius.

Can't say im a fan of knurled rolls, sure plane ones can slip, but generally my experience with rolling is more passes work better and trying to force square - any shaped tube to move faster tends to cause more distortion. A lot depends on your rolls and how there driven though as to how that really works out for any given material. The width between the 2 bottom rollers greatly effects the effective force and that greatly in turn effects the amount of collapse you get when rolling box section based on my experience.
 
I don't have the work order yet so have not done any testing.
I will start with a piece of the ERW, .065 and go from there, as Keith says a little thicker will go easier. 100 wall would be fine.
It is for a table base so looks are important.
Thanks again for all the input.
 








 
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