Miter joint help

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Hi all. Beginner welder looking for some advice on a miter joint fix. Working on the legs for a fab bench using 2"x2" .120 wall square tubing. Used a miter joint clamp and tacked it up, then welded in order from outside corner(welding from inside to outside), butt joints (inside to outside here too), then inside fillet. On both of the pictured pieces, I have 1 leg square with the cross member and 1 leg had some movement from the heat and warping/ shrink so it's pulled in a bit on both assemblies pictured. My inside measurement between the legs closest to the cross member is 20" (which is right), but I had some pulling from the heat bring it in 1/4" on one assembly, and 1/2" on the other at the bottom of the legs. I did multiple passes on each side, so I'm thinking I got the joints too hot. This table will be on casters and get braced on the lower part of the legs near the casters after I completed the top of the frame, but at this point I doubt I can wedge in the right length brace to push it back out enough. I have to go pick up more metal so I'm at a stopping point for now so I thought I'd ask for some opinions before proceeding. Is there a preferred method to fix this like making a relief cut on the outside edge and welding it again to pull the leg back out, or would I need to cut it apart and start from scratch on the unsquared side? Attached Images
Reply:Lots of views but no takers?http://media0.giphy.com/media/jUwpNzg9IcyrK/giphy.gifMillermatic 140
Reply:Try welding a nice hot pass on the outside corner and sanding it off. That will pull it open some, it may get you close enough.
Reply:There are any number of ways you can fix this. 1/2" in 20 " isn't all that bad. You might simply be able to spread the legs and insert your cross bar without too much trouble. You may find a wooden "wedge" can help spring the legs enough to get it in without too much of an issue. I'd cut a 2x4 just a bit wider than you need and with a wedge on one end and see if I couldn't simply tap it in with a hammer to widen the spacing. A bottle jack would open it up no problem. Plenty of other solutions depending on what you have available. I've used ratchet straps to fixed items in the past to open up or close down warped steel.It's possible to heat shrink this back to straight with a torch, but I'm not great at that. I'll leave that to the master, Farmer Samm.It's also possibl eto slice it open with a slitting wheel and reweld it, but you will have to cut 3 sides to make this work, and you will have some gap to deal with on the sides.Understanding how metal pulls when welded will help in the future. Joints almost always want to contract when you weld them. On your corner you had a couple of options, You opted to weld inside, then outside, and then the sides. When you welded the inside, it pulled that way, and the weld on the outside couldn't pull it back. If you had gapped the joint, you may have had the room to make adjustments after the 1st weld and the outside weld could have pulled it back straight. If instead, you had welded the sides 1st, the inside angle probably would have stayed square. Instead you would have run the risk of the legs twisting to the side as it pulled. In some cases you need to decide what is more important, a square corner, but some twist, or possibly an out of square corner, but no twist. Choose your weld pattern accordingly.Judging pull on something like this comes from experience. It also helps if you take some notes when you do projects like this so you know in the future what does or does not work well..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Thank you for the replies. I welded the outside corner first, after having read up in the proper order to minimize the pulling. I welded the inside joint last, for exactly that reason. Having the lower leg support there to begin with would have been ideal in retrospect I guess. Live and learn. I had everything fit up flat on the concrete with the miter clamp upside down on top to get it as flush and square as possible. I beveled all edges, so there was a slight gap to begin with I suppose. I really think the Multi pass on each joint with only a couple mins between welds put too much heat into the piece. So a small relief cut at the top corner, then wedge a brace down near the bottom of the legs, then weld the relief cut? I will be getting more metal sometime this week, just gotta find time to get back to it...Millermatic 140
Reply:Yeah I think having the bottom support there to start, tacked in place, would've solved a lot of your pull in issue - if not all of it.
Reply:Yeah on something like that you only need one pass on each location.  Remember you only need as much weld as the thinnest piece of material used in the joint. Since the tube is 11 ga- 1/8", you only really needed a 1/8" weld. Since that's about the minimum most can do with mig, you already probably had more weld than you needed on pass #1.I'm not visualizing where you want to make this small cut. If you cut only the outside corner, the side welds are still going to keep the joint from wanting to move at this point. They have to go too, especially if you put in a ton of weld bead that might be below the tube.I was thinking you might simply get enough flex to get things to fit without messing with the existing welds. No way to tell without trying. If I couldn't get the flex I needed, then I'd start looking at cutting the existing welds to give me more flex..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Look like you over welded the joint,a single pass would have been plenty.Get some scrap and practice a single weld joint that looks good.You shouldnt have to grind a weld.
Reply:Originally Posted by MillerMig760Thank you for the replies. I welded the outside corner first, after having read up in the proper order to minimize the pulling. I welded the inside joint last, for exactly that reason. Having the lower leg support there to begin with would have been ideal in retrospect I guess. Live and learn. I had everything fit up flat on the concrete with the miter clamp upside down on top to get it as flush and square as possible. I beveled all edges, so there was a slight gap to begin with I suppose. I really think the Multi pass on each joint with only a couple mins between welds put too much heat into the piece. So a small relief cut at the top corner, then wedge a brace down near the bottom of the legs, then weld the relief cut? I will be getting more metal sometime this week, just gotta find time to get back to it...
Reply:I would use a medium tip on an acetylene torch, heat the side that needs to shrink. when it becomes red, it becomes plastic. In the cooling progression it returns to solid, then begins to shrink. this will draw it square. Heat straightening is common practice with steel. Learn the angle needed to pull to 90 degrees and start there in future joints.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:Here you go, easy fix. Use a small welding tip on your O/A torch.When working with square tube, which is very reactive to heat. it’s all about where you place your tacks, and weld sequence. I monitor the squareness with a trisquare or framing square, and diagonal measurement. then determine where I will place my welds. 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:Thank you all for the feedback, very appreciated. I don't have a torch to heat this sucker, so my options here are to grind down the outer weld and butt joints and re weld, or just try to wedge a brace and see if it moves enough. I've already come to terms with living with it as-is worse case scenario, but thought I'd pick some some brains here to see if I had any options.The Multi pass was more for assurance since I don't have faith in my welds yet. My first couple passes on this project I found myself trying to fill the beveled joint and I must have gone too slow because I blew through in a couple spots, so I went full kill and one thing led to another. I haven't had more than a few mins of weld time before this project since I competed my Weld 100 class a year ago, so machine time will do wonders for me I think. I may have made too agressive of a bevel too come to think of it. Part of the reason I grinded the welds was to make it flush enough to lay flat on the ground so that when I went to weld the next joint it would sit flat to keep everything square. Sucks working in the ground, but then again that's why I'm building a table!Millermatic 140
Reply:You can put enough heat there with a Mapp torch on that size tubing. Handy to have around.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