Technical Unbend tubing?

I've corrected round and square tube small CLR bends by using a hydraulic press, or the prying method shown above.

If you're doing subtle arches in a tube roller and you over shoot a bit, sometimes you can get away with flipping the tube over in the roller, and applying pressure as you roll. I've done that with square and rectangle tube, not sure it would be successful with round tube, as it would want to flop over.

 

I think your overthinking this. And do it cold. Lippy

 

Dave I just came upon this thread, I might have a length of 1.5 x .090wall Dom I'll look tomorrow. If I do you can have it.

Pat

 

I always go a little past when bending-much easier to take a slight bend out than trying to pt in back in the bender and add some-taking a slight bit out tends to relieve some of the tension in the tubing from bending. Be aware that taking some bend out tends to open up the bend radius slightly-this can be used to your advantage when fitting a tube where you want it-my frame jig is heavy enough that I have a couple spots i can hook the tube in to pull on it

 

Not probably fitting for an automotive site but it has come in handy when bending tubing on a a car or engine; when I was an apprentice electrician with Standard Oil of California a journeyman training me put 3-4 bends in a 10’ stick of 1/2” rigid conduit handed me the hickey and told me to take them out and the conduit had to roll on the floor when I was done. Later he did it with emt thin wall and that was a bitch to do. I quickly learned to measure twice and bend once..

 

as you do more bending you'll notice that ERW,Dom or 4130 all have a different amount of "spring back'-telling you how much past the degree mark you need to go

 

Lay the tube on the weld table and c' clamp at the bend. It will unbend some; provided you can tolerate some reduction of diameter at the bend but it is probably deformed some from the bend anyway and will be actually making it back to round...

 

Ahhh the other million th use for the forklift

 

In 40 years of bending tubing I've found it's very easy to get a couple degrees over or under with most benders. But it's way easier to take it out than it is to put more in. Often I've simply grabbed one end of the bend and given the outside corner a sharp rap on the concrete floor and it knocks a degree or two out. If it needs more than levering it under something heavy can easily remove 5 degrees if needed.
Putting a degree or two in can be done by holding one end straight up, and smacking the other end of the 90 on the floor to close up a bend. But don't try to get more than 1-2 degrees this way as it can close up the 90 and make it oval instead of round.

 

Thanks for the offer. I am not out of tubing however. Just being a true Scots! I have 5 1/2 more 20 foot sections of the stuff from a recent procurement of steel. It's just that half of me is chea... er, that is thrifty!

 

I get it now! I do have some tubing though if anyone LOCAL can use some.

Pat

 

Yes, that's an interesting point. Yesterday making the 2 layout test bends I dutifully recorded the spring back for the 2 different sizes. The 1.5- 0.095 is 4 to 5 degrees and changed slightly as the bend got above about 60 degrees.

The 1-0.120 had similar results, being about 6-7 degrees up to around 70 degrees, and being a full 10 degrees by 180 degrees. Like I said I dutifully recorded the spring back and have it written right on the test bends. Hopefully I'll pay attention to the notes and not uck fup later when I make some squiggly tubes today.

 

Marty getting it done with the Armstrong method. I had to give it a try on a "practice " bend from the scrap rack. Using the neighbor's stone bar, it was easy, 3 or 4 degrees and no noticeable deformation. Maybe later today I'll try the whack it on a tree stump method just to compare. I do after all have a selection of "practice " bends to experiment with, being Scots heritage and all...

 

I never of thought of using my forklift, it weighs 7300 lbs.

 

All done in flip flops no less…..

 

Interesting that Dave G mentions it,but anyone I know that bends tubing has a greasy,well worn spiral notebook near the bender with notes only he can understand!!!LOL

 

I have had a notebook forever. Started in hs, got me out of a fight once. Been keeping notes ever since. Why try to remember something when 10 seconds of effort keeps it until you loose the notebook.

I'd use notes on the cellphone more, but I find it easier to look stuff up in written form.

 

Try heating the outside if the bend start at one end of the bend heat it red hot about 1/2 way around the tube side to side and work your way around the bend leting it cool behind as you go. The same reason long weld beads pull the metal.