Correcting 2x1" square tube bend

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Hi all,Novice question...I am welding some 2"x2", 1/8" thick flat bar rectangles to 2x1" square tubing on the 2" side, all on one side of the tubing.How do I correct the distortion of the tubing after welding seven equally spaced squares? Heat up on the opposite side of the tubing in various places, or just beat on it?My 2x1" tubing is 72" long and I do not have anything big enough to clamp the whole piece to...Thanks a lot.
Reply:Although probably won't be perfect and will still require some tweaking, clamp the tube to a good sturdy bench with spacers under the tubing so it's prebent the opposite way. Start with maybe 5/8" thick under the middle one, 1/2" under the 2 either side of center and 3/8" under the 2 either side of those and then clamp the ends down to the bench.If youre doing more than one, clamp or tack them back to back with spacers between them....Mike
Reply:negativ3Stick, TIG, or Wire?Are the welds full perimeter - if not, how small can they be?The short answer: you pre-camber each weld section - before welding,to compensate for the shrinkage.  With practice - you can dial-in, a perfectly flat - after weld profile.Post Weld - it is easier to correct  'pre-camber/over compensation'welds - then it is to wrangle raw weld shrinkage [welds].Not having an 8 foot table is less than best - but you don't need one. You only need: a surface, long and strong enough, to pre-camber each pad weld section.The gauge of the table, and the clamps required: are a coefficient ofyour weld process, and weld size.Opus
Reply:Thanks guys,Tig and the welds are full perimeter.Question... bending the tube in the opposite direction means the pads will not be flush with the tube when welded?
Reply:You will need to find somthing as long as that piece you want to weld. So you can clamp it on there with a bunch of clamps. Pre camber is a new one for me
Reply:negativ3You tack the pads before cambering. Why are the pads welded - full perimeter?What does this weldment do?Depending upon application - there maybebetter joining alternatives . . . Opus
Reply:Opus, ahh, ok, these will be uprights for a gate. Pads are for centre drill & tap for horizontal slats of wood to bolt to.All components will be subjected to the elements hence full welds to prevent ingress.Moto, will another piece of tubing be strong enough or will it need to be stronger than the tubing?Say I have one piece of tubing welded up already, shaped like a banana , what could be done to save it, or ditch and begin again?
Reply:You could clamp it to a heavyer piece of tube like 3/16 or bigger. And put a bunch of heat into your welds and it will probably straighten out. Don't unclamp it tell its cold. If the piece was fresh with out any welding yet I would think the same tube you are welding on now should get the job done. Try it see what happens. Use a many clamps as you can if you put alot of heat into it
Reply:Bigger is usually better in welding
Reply:If you start fresh you could clamp as thick of a piece of copper or aluminum to the sides and top of the tube you are welding that will that the heat out of it and make it weld really nice
Reply:use the banana shaped piece to clamp the tacked pieces to. shrinkage forces during welding may straighten out the original bent piece.i.u.o.e. # 15queens, ny and sunny fla
Reply:Cheers moto, will give it a go.
Reply:Originally Posted by negativ3Opus, ahh, ok, these will be uprights for a gate. Pads are for centre drill & tap for horizontal slats of wood to bolt to.All components will be subjected to the elements hence full welds to prevent ingress.Moto, will another piece of tubing be strong enough or will it need to be stronger than the tubing?Say I have one piece of tubing welded up already, shaped like a banana , what could be done to save it, or ditch and begin again?
Reply:Give us a quick sketch of your fence design. I have built a lot of fences, and am not quite clear on what you are trying to accomplished, but am sure I could come up with a better design alternative.
Reply:Thanks very much for the offer walker. I have been out and tried clamping along the length and heating and it has taken out a considerable amount of distortion. I will get a sketch done once I get a minute.
Reply:I agree on over welding. Just weld parallel with the tube and it will the same as when you started. Make another like you did and you have a ramp with a camber to it . I did that intentionally to have a arc to them.
Reply:You could try either one of these techniques. I don't think heating the heels of the opposite side of the tube will work in this case.I think you'll need to heat a wedge down the small side of the tube, then across the back side the same width, or maybe a little bigger than your clip. I would use a large welding tip, or a small cutting tip on your O&A torch. Start in the center heat that area red hot, cool with water. Don't move to the next location until the first area is stone 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:over weld in my opinion, if these are just holdign wood slats you can just epoxy them on? cheaper and faster IMHO.with no water getting inside.
Reply:Or you could even avoid all this welding, drilling and tapping scheme... and just install rivetnuts. I understand you need the extra thicknes of those pieces of plate in order to be able to drill/tap and get enough threads... Well, you can acomplish this very same thing with rivet nuts. If you fear only one bolt might not be enough, you can install two or even three. No worries about distortion!
Reply:No need for heat. Find a fork, tree, trailer hitch  etc. and bend it straight. it is just 2x1 bending the easy way.  If you had multiple to build, then you could tack back to back and fabricate.  Do a few and you would know how much to offset each middle to get them straight.Last edited by tapwelder; 01-05-2015 at 11:54 AM.
Reply:that is not a good design. too much of a negative impact on the gate squareness for the sake of locating the slats. locate the slats without touching the lower or upper perimeter frame. or just JB Weld the brackets if you must keep that design.
Reply:Why don't you just use thicker tube (3/16" instead of 1/8" if that is what you have)? Wouldn't that work just as well? Plenty strong or stronger than what you are doing, enough thickness to tap, no water leaks, look better, and cheaper than what you are doing. If you say the weight would be too much, I am sure the wood is where the weight is, not the tube.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:Thanks for all the suggestions guys. I will try epoxy on the next piece.Its really just an excuse for me to get some hood time for tig . Prefer to learn and build as well as lay pads of beads...
Reply:those rivetnuts are cool, I have another project they will work well on.
Reply:Lot of good advice from all. I weld up hog traps a lot and when I do the frame for top and bottom i tack every corner then make sure I'm still square. Now im ready to weld I will start in one corner then go to opposite corner. What im saying is to tack um all check um then weld first one then weld last one then let it cool then maybe middle one then second one then second to last and so on. I wouldn't weld first one and then next and keep the heat going straight down the tubin. I jump around welding cattle panel to angle iron on trap if not it will cause a bow in middle of angle works good when I jump around.Originally Posted by negativ3Thanks for all the suggestions guys. I will try epoxy on the next piece.Its really just an excuse for me to get some hood time for tig . Prefer to learn and build as well as lay pads of beads...
Reply:Box tubing and pipe are the most reactive materials to heat I've worked with. A lot of times I'll skip weld, and use caulking between the welds before painting. That way water won't get between the two objects. 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:a simple google search will give you ideas on a non-welding or minimal welding solution.http://www.allsydneyaluminium.com.au...wing-gate1.jpg
Reply:Originally Posted by CEPYou could try either one of these techniques. I don't think heating the heels of the opposite side of the tube will work in this case.I think you'll need to heat a wedge down the small side of the tube, then across the back side the same width, or maybe a little bigger than your clip. I would use a large welding tip, or a small cutting tip on your O&A torch. Start in the center heat that area red hot, cool with water. Don't move to the next location until the first area is stone cold to the naked hand.
Reply:Someone might have said it in the beginning, maybe concaving the 2"x2" pieces so that those "warp" back to flat when welded?
Reply:Originally Posted by MinnesotaDave+1, This works very well.As noted by others, welding across the face is the worst for causing the bow in the material.Check out Mr. Shrink video for some background information."Prevention and Control of Distortion in Arc Welding"
Reply:Originally Posted by TigMonsterI cant believe i just watched all of that...at work.
Reply:Originally Posted by MinnesotaDaveIt's an excellent video I like most of the old ones vs the new ones
Reply:Put some stress on that thing in the way you want it to bend, then heat it on the opposite sides of the welds in a pie shaped pattern like they've said.  Find out how it behaves, and adjust accordingly"Any day above ground is a good day"http://www.farmersamm.com/
Reply:What is the friggin mystery about heat straightening????????????????????"Any day above ground is a good day"http://www.farmersamm.com/
Reply:No need to call Scooby doo yet, just a noob question about a banana shaped tube Thanks all.
Reply:negativ3Your welding conundrum is actually a design issue.This is a technique/joint I use when I need more 'thread-grip' than the tube-wall is thick.You add the 'nut-meat' to the inside.Select a Flat Bar for 'gauge & width' that will provide the add thread-grip.Cut the FB 1/8" shorter than your tube.Layout the holes on the FB, center punch; then tack the FB to the exterior of the tube per design locale.  Select your desired tap-drill - and drill the holes.  Snip the tacks - and tap the FB.  Re-drill [enlarge] the tube holes to your bolt size - no larger.This is the 'nuisance part' - each of the bolt holes require an adjacent hole in close proximity for a plug weld.All the plug welds do is hold the FB's location for bolting, so the weld can be very small - typically, only an .125" hole - sometimes smaller.  If the tube wall is too thick for easy electrode access, do not drill a larger hole, but chamfer the top with a countersink.  Make an effort to leave a 'land' on the side-wall at the bottom - for 'burn-in' when welding. Next: thread the FB into the tube, bolt each hole , plug weld and dress, then cap the tube.This is: a 98.1618% reduction in weld area, your tube has thread-grip, it is stream-lined on the exterior, and it is straight - via - smoke & mirrors.Good design excludes repair as a necessary step . . .OpuspsAlways look through the other end of the telescope . . .
Reply:If you clamp the straight piece  with a spacer under it to pre bend it the opposite way it might work.  It would be guesswork how much to pre stress it. However it will leave it straight enough you may be able finish straightening it by hand.  If you could weld the pads on the outside edge only it would help too.
Reply:Thanks Opus, I'm going to give that a try. It will increase weight a bit but like you say, covertly.Thanks all, learning a lot here.
Reply:use self tapping screws to hold the plate in place,  they are made for thin metal.  grind head off, or drill til head twis off.  If you twist the head off then you can still practice tig welding by plug welding the void.  Or use self tapping screws through the wood into the tubing.   I have purchased self tapper meant to drill through wood.  The self tappers through the wood work, well I use them when I mount wood on metal gate frames I build for a client.Concerning the prebending.  If I already have one part jacked up.  I will use that part to determine how much to pre pend.  I clamp on end to a table and measure how much it rises off the table at the other end.  Half that measure is the amount of pre bend I add to the middle.Last edited by tapwelder; 01-08-2015 at 09:41 AM.
Reply:I got bit by this once building a railing. Top rail with a lot of stringers hanging down. After welding the stringers to the top and set the whole thing up on edge the middle was 1" off the ground. Fortunately that railing had perforated steel sheet for fabric. I was able to bend the thing straight, lay the perforated sheet over it, weld it to the sheet and the edgewise stiffness of the sheet held it straight. Whew.Nowadays if I have to do a bunch of welding on the side of a long tube I take a strongback (usually a piece of much heavier tube) and put a hydraulic bottle jack in the middle of the tube I'm welding to and put a couple of 1 foot web slings between the ends of the strongback and the ends of my tube and jack up the jack until the ends are bent up noticeably. Like about 3/8" over 8 feet. Then weld, then let go of the bottle jack and everything lies much straighter.I'm thinking the gate would be worst case because your piece has nothing to weld it to to keep it straight.BTW the guy who showed how to hot bend your part got it 100% right. Heat shrinking works -- it's how they curved the massive beams that hold up the Seattle Space Needle. Old guys with torches, patience, templates. metalmagpie