I know there's got to be a trick, but what ?

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I just do home tinkering and love working with square tubing. Try as I might though, I cut precision lengths of material, square it up perfectly and when I'm finished welding 4 pieces into a square, it's warped with two catty-corner sides always higher than the other two. I know it's the heat that's pulling things out of square, I've tried tacking all 4 sides, alternating sides that I run beads on but regardless, when I'm finished my square won't sit flat on a surface. Any tricks to keep this from happening that I can't figure out ?
Reply:Clamp it to a table, tack and weld equally on all 4 corners, let cool and unclamp, force back to square as needed.
Reply:Is it stainless tube? Have you tried clamping it all down before welding? This will help prevent weld distortion. Do you have bar clamps? They work great. You can get the ones that go on the ends of 3/4" threaded pipe, then put one on diagonally to hold it square when you weld it, or to bring it back to square if it racks. But you shouldnt need all that if it is regular steel. If you just set it square and tack the outside corners and then tack the face an inside corners it should hold square for welding.Welding everything, from the crack of dawn to a broken heart.
Reply:It's just plain old steel square tubing. Yeah I've got some bar clamps so will try clamping it all down next time. Just frustrating as H, E double L when you try so hard and after it's all put together, it's turned into a teeter-totter.......
Reply:one way is to fit it up wrong and let the weld pull it into position..experiment with some scrap to see  which way the weld pulls depending on the sequence you select and use that to see how far out of sguare the fitup needs to be to end up where you want it..
Reply:Looks like the previous replies are focusing on the frame being out of square after welding. If I'm reading it right, the problem is not being out of square, but not laying flat, not all in the same plane. If that is the case try grinding the welds on two opposing corners on one side and re-welding to see if the heating and cooling will draw it back in that direction. Or if you have a good flat welding table, clamp it down good and flat and heat two opposite corners with an O/A torch and let cool before un-clamping.
Reply:I used to tack all four corners just on the inside of the top corner with everything clamped down. Tack just inside enough that the tack won't protrude above the surface of the metal. While doing this, of course, you have to make sure everything stays square, too. After tacking, all the tubing WILL have twisted upward (especially when you un-clamp it). Flip the whole piece over. You should notice the gap being wider on the untacked side, which is now up. Clamp the thing at all four corners and it should pull it back flat. Repeat the tack procedure again. When you unclamp, it'll stay flat as can be. Of course, the key to this method is having a nice sturdy table to clamp to.
Reply:Bistineau, I didn't quite know how to describe it, but you've hit the nail on the head with what my problem is. I'll try your methods. Zmechanic, you've mentioned something that's a problem due to my error too. When I built my welding table, I had no idea really what I was doing other than welding together some heavy metal to make a table. I've used a 3' x 4' sheet of 1/4" plate steel for the top. Just home tinkering and not having a shop to really work in, I wanted a semi-light table that I could still maneuver around under my carport, thus the choice of 1/4" plate steel. Well, I welded my table frame together, then laid the sheet metal on top and welded it to the table frame top...... You can guess what my problem is..... it pulled the sheet metal in the welded spots making it a tiny bit warped around all the edges.......
Reply:You need to understand WHY things move due to welding. Joints will almost always pull towards the bead. Lets look at a miter joint. We'll label the inside seam "A", the top seam "B", The outside corner seam "C" and the lower seam "D". If we lock the 1st piece to the table and weld the inside seam "A", the joint will pull out of square and open up seam "C" making the joint less than 90 deg. The opposite would occur if we welded the outside 1st and welded seam "C", the  joint at "A" would open up and the corner would now be greater than 90 deg.Now instead, we weld the top seam "B" instead. The lower seam "D" would open up and while the joint may remain square and we have a 90 deg corner, the 2nd piece will not lay flat, but rise up off the table.One trick to combat all of this is to gap the pieces slightly so you can bend them back to where they need to be after tacking. Smaller beads, less heat, the less likely things will move.The other trick as mentioned is to deliberately  set things out so they pull back to where you want them. In this case you might set the 1st piece op on some 1/16" tig rods with the lower corner supported and a slight gap at the top, then weld seam "B". The lower seam "D" would then open up ( hopefully the right amount) and you can then weld that one as well. Attached Images.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:Originally Posted by rico334Bistineau, I didn't quite know how to describe it, but you've hit the nail on the head with what my problem is. I'll try your methods. Zmechanic, you've mentioned something that's a problem due to my error too. When I built my welding table, I had no idea really what I was doing other than welding together some heavy metal to make a table. I've used a 3' x 4' sheet of 1/4" plate steel for the top. Just home tinkering and not having a shop to really work in, I wanted a semi-light table that I could still maneuver around under my carport, thus the choice of 1/4" plate steel. Well, I welded my table frame together, then laid the sheet metal on top and welded it to the table frame top...... You can guess what my problem is..... it pulled the sheet metal in the welded spots making it a tiny bit warped around all the edges.......
Reply:Have you tried leaving a small gap in the joint.  This way when the tack weld shrinks it'll just shrink straight in.  If you didn't have a gap and the joint is touching somewhere away from the bead, the only way the bead can shrink is if the two pieces rotate (and they will).Tack all corners on all joints before trying to weld it upDynasty200DX w/coolmate1MM210MM VintageESAB miniarc161ltsLincoln AC225Victor O/A, Smith AW1ACutmaster 81IR 2475N7.5FPRage3Jancy USA1019" SBAEAD-200LE
Reply:Great explanation DSW.... proof that a picture is worth a thousand words, that all makes sense plus what AndyA mentioned..... Thanks guys a whole bunch, I'll be practicing with these ideas this weekend.
Reply:Originally Posted by rico334Great explanation DSW.... proof that a picture is worth a thousand words, that all makes sense plus what AndyA mentioned..... Thanks guys a whole bunch, I'll be practicing with these ideas this weekend.
Reply:Something not mentioned is tack welding several pieces of scrap diagonally across the frame to form triangles.  The braces are tacked on after the frame is assembled with tacks and is checked for square and flatness.  You tack the scrap to the frame lightly and on one edge so that you can twist and snap them off afterward.  This is standard procedure when the frame is larger than any table you have.
Reply:Thank you DSWReal world weldin.  When I grow up I want to be a tig weldor.
Reply:I clamp both pieces to the table, tack the out side corner at the top then weld the full inside then outside then the top. I let it cool then flip.Tim Beeker.