Tubing help...flat spots

I'm redoing the backhalf on my mazda and recently bought some 1.25 erw with .120 wall.  I have used dom in the past that was .188 with not kinking or flat spots but now with the new tubing everything gets a flat spot in it.  I'm just bending a couple of 45s but no matter what I do it has flat spots.  The reason I changed to the erw with a .120 is b/c I read that a few others on here are using it as well.  Also, I used the JD2 model 32.  If anyone can give me any tips or helping info as to why it is creating flat spots it would be greatly appreciated.  I will probably just go back to the dom if I cant get this fixed.

i cant tell you the scientific reason that the erw stuff has flat spots after you bend it, i have an idea but rather than look like a fool lol , i will just tell you that the erw stuff does the same on my bender, with the same wall thicness.  Thats just the nature of that kind of material.  I use it alot on stuff that is not structural and dosent need to look great.   go back to dom and you wont have an issue, the price difference sucks ass, but thats all you can do really to get the true bends.  Taylor

---------------------------------------------Originally posted by Chopped Mazdai cant tell you the scientific reason that the erw stuff has flat spots after you bend it, i have an idea but rather than look like a fool lol , i will just tell you that the erw stuff does the same on my bender, with the same wall thicness.  Thats just the nature of that kind of material.  I use it alot on stuff that is not structural and dosent need to look great.   go back to dom and you wont have an issue, the price difference sucks ass, but thats all you can do really to get the true bends.  Taylor--------------------------------------------- Thats the answer I was looking for.  It makes me feel better that someone else has the same issue and it isn't just me.  I really appreciate the help.

I also have read where some of the guys on here us it on the backhalf but how do they not get the flat spots or do they and you just dont notice?  I would don't feel comfortable with it having flat spots and unfortunately i'm about out of dom.  Around here it has to be ordered so I won't be able to finish this week unless i can find a way to use the erw.

From what i can remember... i could be way off on this one... both ERW and DOM tubing are both formed through cold rolling and welding which makes the metal strong, stiff, and not very ductile (bendable/willingness to stretch and deform).  The ERW typically only has the welded seam annealed leaving it still rigid and not very ductile resulting in flat spots during bending. Where as the DOM tubing is usually fully process annealed making it more ductile and likely to stretch and bend without creating flat spots. In a nut shell, the annealing process of the DOM makes it more ductile than the ERW meaning the DOM is more bendable and less rigid and stiff. Heating up ERW tubing before bending, not too hot though, should anneal the tubing and make it easier to bend without creating flat spots. Again I could be way off and possible made myself sound like an asshole.

I might try that.  Now would be a good time for Max or Seth to chime in as well.  I'm sure that I read that Seth uses this on his projects so maybe he knows something that I don't on how to stop it from getting flat spots.  I will try heating it tomorrow though and let everyone know how that goes.

i am not a fabricator by any means, but i have always heard people packing the tubing with sand prior to bends to prevent flat spots, but that is with using cheap ass benders. If i'm way off then disregard just one of those backyard redneck things my uncle always said.

Thats a great idea as well to try.  I think I will end up trying both of these tomorrow.  Only thing is, to me it wouldn't seem like the sand would actually prevent it but then again there are a lot of ways to do things out there that I wouldn't believe until I tried it.

the sand trick is hard to acheive from what I hear and I honestly don't think it will help you much.  I thought the sand was mostly used for really thin material, such as exhaust pipe

Post a picture of what it's doing. I've never had welded tube go flat after bending it. I'm working with some DOM right now for a cage, and it looks the same bent as ERW. I bent the first tube in ERW in case I messed up, since it's 1/3 of the cost.