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Tube bending formula

Tube bending formula

Tube bending formula

(OP)
I haven't been able to find a formula for bending square tubing.  Typically we cut a few pieces until we get it right, but there has to be a way to calculate this without going through several stocks of tubing.
 
For example:
1" square cold-rolled steel tubing
45 degree bend
2 1/2" inside bend radius
leg 1 = 35"
leg 2 = 21 1/2"

Also, a formula for round tubing would be great also.

Flores

RE: Tube bending formula

Not sure about tube but for sheets I always start with

(2/5 thickness + inside rad) x 6.28 =360 degrees and then build in a factor for the material through experimentation, this gives the development for the bend.

So for the example you give

(2.90) x (6.28 / 8) = 2.46” so assuming the lengths of 21 ½ and 35 are flat lengths and not to intersection points the length would be 58.96”

This should give you somewhere to start and from there I would factor in any errors and see how different wall thickness etc change things through experimentation.

The more you refine the closer you will get.

Hope this helps.

RE: Tube bending formula

(OP)
Thanks Ajack, but I was hoping  someone had a formula for square tube.  For sheetmetal bend dedcutions, I use Bendworks,
http://www.massey.ac.nz/~odiegel/bendworks/

But, because of the side walls in square tube, Bendworks isn't perfect.  For 90 degree bends, a k-factor of .6035" seems to work pretty good, but I can't find a suitable k-factor that works for all angles.

Flores

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