Straighten bent steel from weld?

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Hi guys, I'm sure this has already been asked before but since I'm new I'm going to ask again.  I have 2 welded table legs that have 2' flat bar as the base and top. They started straight but the top now has a slight bow to it.  Is this something that I can exert a little sweat with a mallet and get back into shape or is the answer more involved?Thanks so much for your help/expertise!!
Reply:Looks like you are going to use the upper flat bar to lag bolt the legs to a wood surface. Not how I would ever do it but the lag bolts will pull the flat bar flush to whatever you are mounting them to. If you use a single row of lag bolts to hold the leg to a wood surface, you just installed a pivot that will wobble no matter how wide your flat bar is. You need two rows of lag bolts to not be a pivot. Consequently the width of your flat bar is important. Especially with what looks like standing height table legs.FYI I would never condone using lag bolts in furniture.
Reply:Something that thin, I’d smack it with a hammer. Any thicker, then I’d heat shrink it back into shape.Don’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:your problem has many good solutions, and the same end result can come from many different methods.with that said, this is what i would do;-first, try a hammer if you have a big enough hammer and a sturdy enough 'anvil' to beat against. of course hammer may leave unacceptable markings.-second, clamp the piece in a vise and use the length of the leg as a lever to bend maybe even a a pump jack to put enough force on it.  this may lead to an offset bend the will leave you with a more or less flattened piece but with a noticeable bend.-third, heat pulled it down... heat can pull it back. you can use a torch on the opposite side on the weld, use a flame that will heat the metal just short of melting or cutting. then run the torch opposite of the weld moving on as the metal is 'cherry' hot. one pass you want direct focused heat, not a back and forth that allows the heat to spread, just one slow pass.  little bit more of a learning curve than brute force, but you get back waht you put in*you may find that combining methods, ie clamp heat then bend, yield best result.** to avoid problem in the first place firmly clamp to suitable work surface then weld, remove once weld has cooled.Last edited by tracymobilecnc; 12-05-2015 at 05:36 PM.
Reply:That was how I was planning to do it. Can you go into a bit more explanation about the pivot that will cause the wobble just so I can understand?  The width is 2" so If they were staggered I could have two rows of lag bolts.  Would that help?  The height is only 29" so its sitting height if that affects anything.  If not lag bolts, what would you recommend?
Reply:If you heat shrink, I’d use a large welding tip, or a cutting tip. Heat where the red lines are. Spray water on the heated lines. Wait until the heated area is dead cold to the naked hand. If this is not enough, move towards the center an inch or two, and heat another line. Spray with water, wait until the heated line is dead cold to the naked hand. Attached ImagesDon’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:Luckily for me, smacking it with a hammer is within my skill set.  I was reading about using heat shrinking but I don't have the tools to do it.  I made these at a maker space and they have a welder but that's about it.  Would a local metal fab place be able to heat shrink it if the hammer doesn't work you think?
Reply:Originally Posted by Jimmy_popLooks like you are going to use the upper flat bar to lag bolt the legs to a wood surface. Not how I would ever do it but the lag bolts will pull the flat bar flush to whatever you are mounting them to. If you use a single row of lag bolts to hold the leg to a wood surface, you just installed a pivot that will wobble no matter how wide your flat bar is. You need two rows of lag bolts to not be a pivot. Consequently the width of your flat bar is important. Especially with what looks like standing height table legs.FYI I would never condone using lag bolts in furniture.
Reply:Anybody with a torch can do this. I’m just a hobbyist, and I can do it. Don’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:Originally Posted by CEPIf you heat shrink, I’d use a large welding tip, or a cutting tip. Heat where the red lines are. Spray water on the heated lines. Wait until the heated area is dead cold to the naked hand. If this is not enough, move towards the center an inch or two, and heat another line. Spray with water, wait until the heated line is dead cold to the naked hand.
Reply:Originally Posted by CEPAnybody with a torch can do this. I’m just a hobbyist, and I can do it.
Reply:Look in your local telephone book for a fab / welding shop. Or stop by a welding supply, they’ll know who can do this for you.Don’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:To prevent this next time , only weld parallel with the flat bar , the long wayLast edited by BD1; 12-05-2015 at 08:36 PM.
Reply:Originally Posted by jswtravelerI was reading about using heat shrinking but I don't have the tools to do it.
Reply:What are you using as a top?Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Originally Posted by Broccoli1What are you using as a top?
Reply:if a welder is what you got, thats fine doesn't have to be a torch.  grind a small relief along the heat line and weld it. let cool then if needed grind down the weld that sits too high. when i make metal to wood furniture i would never want to have a wood top pull the metal back into place, its potential to damage the top isn't worth it.