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Best way to bend 2" .250 wall DOM?

15K views 18 replies 15 participants last post by  maxyedor 
#1 ·
Best way to bend 2" .250 wall DOM?

My Protools Super Bender(http://www.pro-tools.com/sb105.htm) broke the die when trying to bend a piece. I need a couple of bends in a piece for a trackbar we are building. What are others doing to bend this type of material? Suggestions? We are repairing the die for another try but hate to destroy my bender for this one.
 
#4 · (Edited)
The K.I.S.S. explanation: The tube is trying to flatten out when you bend it and that's why you are breaking the lips off your dies.

There's a lot of math involved to fully explain what's happening, but here's the best I can do: The difference in length between the inside and and outside radius for 2" tube on a 5" centerline radus bend is exactly 1.47". In a perfect world the tube would shrink ~3/4" along the inside radius and it would stretch ~3/4" along the outside radius to split the difference, and you would have a perfect bend. [edited for math fawkup]

We don't live in a perfect world and .250" thick steel walls won't shrink or stretch that much without some serious forces (or serious heat) involved. If the tube can push some material out *across* the centerline radius It effectively lowers the difference between the inside and outside radius so the tube doesn't have to shrink/stretch as much. That's why it's easy to bend tube if you hammer it flat - duh!

A bend is nothing but a combination of shrinking and stretching. It's easier to shrink and stretch metal when it's hot. I would sand pack the tube and bend using "open die" technique with a hyd. press or pipe bender with the aid of a torch. You would need one guy to keep the rosebud moving, one or two guys to move the tube around, and one guy to pump the hydraulics on the press (it's kind of a clusterfuck way to get the job done, but it works). If you want an "impossible to make" part sometimes you have to revert to doing things the low tech/old fashioned way. You can use the flame shrinking technique along the inside radius to "fine tune" the degree of bend if it's a critical dimension. You aren't working with 4130 tube, so heat treating isn't a concern.

I don't know anyone with a tubing bender capable of 2"x.250 wall so I can't offer any suggestions if you still want to cold bend the tube. Put a safety blanket over the dies would be my only advice - shrapnel injuries can ruin your day.
 
#6 ·
#9 ·
I'll post a pic when I get my card downloaded of the die. What broke was the part that holds the tube to the die when bending. We rewelded the peice back on and added a gusset and tried the bend again. This time I heated the tube to approximately 350* and shoved it in the bender as fast as I could to start bending. I went real slow and was able to bend it the 15* that I need and then I let it air cool. I'm still not out of the woods yet as I have to make one more bend on this piece of tube.
 
#11 ·
I own the JMR air hydro unit. I have bent plenty of 1.75" .25 wall dom with out a problem at all. I also have a 1.25" Pro tool die that I use on this bender and once you compare the dies side by side it is easy to see why the JMR dies are twice as much.

I too have bent 2" .25 wall dom with my HF bender but a lot of heat was needed to soften up the tube.

Good luck
 
#19 ·
That was me, it was 1.5" OD .500 wall 4130 for a panhard (.500 is way overkill, but I can't argue with free 4130) I used my custom 12ft handle and it bent just fine. Only did 2 bends, never had to use .500 since then, and my 1.5" die is still going strong and gets used constantly.

Looks like the OP broke the weld, not the die, broken is still broken, but seems like all you'd need to do is gussette the "strap holder" right out of the box and you'd never have a problem. Looks like the flaw in the die is that on the 2" die that piece is only welded on 3 sides, my guess is that it flexes right there just barely enough to potentially cause a crack and a failure. Need to order a 2" die in a few weeks, I'll be gussetting mine right out of the box.
 
#14 ·
We bent 1.5x 0.25 DOM a few weeks back. Had to make an extension for the handle, but other than that just good old fashion pull and reset and it bend it just fine

Pro Tools 105HD



 
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