Welding a large item with no table?

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I read some older threads, but don't have a clear idea of what to do when the project is bigger than your table or in my case, I have no table at all...The item will be a 5'x2' frame with rails every ~18" or so to be used as a tool platform. I want this to come out flat (all pieces in plane). I read some interesting things in: http://weldingweb.com/vbb/showthread.php...ighlight=miter DSW's overview of tacking and lotechman's interesting comment on tacking a temp diagonal to keep things square.Does this mean the project is tacked and welded on the ground? I am leaning towards mitered corners with edges knocked off, but waiting on another thread to finalize that...Any advice for clamping? Would a piece of plywood with strips of wood acting as stops to keep things in place work?AC-180 Lincolnwelder circa '50's
Reply:I do it all the time.  The best trick I know is to use spacers so you don't have parts rocking on a hump in the middle.  I also use my saw horses and can shim them to be level one direction.  The other direction doesn't matter.  Tack up your frame and flip it over.  If it still sits good on your spacers, then you're flat.  If it rocks, break a few tacks and try again.My name's not Jim....
Reply:Build the frame on the floor, use a turnbuckle on one corner, adjust it in or out to get your diagonals the same, add the cross peices once the outside frame is good, weld and flip, weld and your goodUA local 32Team weld-coolTeam miller elite tack upMiller pro-staff
Reply:Once set the turnbuckle will keep things square, other junk peices could be added to the other corners after square for added securityUA local 32Team weld-coolTeam miller elite tack upMiller pro-staff
Reply:A bit difficult to describe but what you need are two horses of supports slightly wider than your frame.Set them across your work area and check with a spirit level ( two footer at least) They must be level across but it is not necessary for them to be level between.    Set your two frame rails on the crossmembers and then connect your ends.  Now you have a frame tack welded together and you can "turnbuckle" it square. .. like fishin said.   Add your crossmembers checking that everything stays square as you tack it together.   Finally add some temporary diagonal braces.  The more the better.     Now you are ready to weld. Jump around never completing a joint in one go.  Imagine you are tightening down cylinder head bolts.
Reply:I am not sure about the turnbuckles, can't picture how to attach them. Are we talking tack weld on at each inside corner and put some steel cable between and crank until square? I do have some 3/4" pipe clamps that are over the diagonal distance I need, my concern is how to make sure the frame doesn't hourglass out of the flat plane, the clamps can keep it square, but the up down is what bothers me...Lotechman, would a grid of 2x4's leveled work ok then?AC-180 Lincolnwelder circa '50's
Reply:Hello chopnhack, here's an example of an angle clamping fixture that can help with free-form framing. I've included a couple of pictures showing a type of clamp there are plenty of other similar systems that could be used. I have a number of other pictures that include the use of turnbuckles and a few other types of frame set-up type illustrations. Some of them are pics that show what others have suggested in some of the previous posts. Unfortunately, they are on my computer at work. I'll see about including them when I get back to the office. Best regards, Allan Attached ImagesLast edited by aevald; 02-26-2012 at 03:16 AM.aevald
Reply:Originally Posted by lotechmanA bit difficult to describe but what you need are two horses of supports slightly wider than your frame.Set them across your work area and check with a spirit level ( two footer at least) They must be level across but it is not necessary for them to be level between.    Set your two frame rails on the crossmembers and then connect your ends.  Now you have a frame tack welded together and you can "turnbuckle" it square. .. like fishin said.   Add your crossmembers checking that everything stays square as you tack it together.   Finally add some temporary diagonal braces.  The more the better.     Now you are ready to weld. Jump around never completing a joint in one go.  Imagine you are tightening down cylinder head bolts.
Reply:I use a piece of 2x2x1/4(can be larger than 2x2) angle iron clamped into each inside corner. Weld topside, flip it and weld topside again, then outside corners. Then remove the clamps and weld inside corners. Use the same set up to square up the other pieces in between the ends. If you have enough clamps and angle pieces, leave the corners clamped while adding the other stringers in the middle. This works with butt welds or mitered corners, square tubing or angle iron. Attached Images
Reply:There's a million ways to do it, put some thought into it and I'm sure it will turn out goodUA local 32Team weld-coolTeam miller elite tack upMiller pro-staff
Reply:Hey Aevald.........Way cool fixture   dont need one now, but gonna make one now!!!!!!!
Reply:Originally Posted by chopnhack...Lotechman, would a grid of 2x4's leveled work ok then?
Reply:bevel the edges of a miter cut and weld, depending on the frame, grind the needed edges flush with a flapper wheel. pump skid frame. UA local 32Team weld-coolTeam miller elite tack upMiller pro-staff
Reply:Hi sheet rock square ,framing square , pipe bar clamps , angle magnets and a tape should be all you need. We build 100. ton pieces on skids. all the time.  John
Reply:Awesome guys, I didn't realize how much the jigging is like woodworking. I was concerned because of the movement of the steel with the heat of welding. But I think I got an idea now! Thanks Bistineau, if you weld the top seam, doesn't the bottom spread open? I was thinking of tacking everywhere first, making the last squaring adjustment and then doing the full weld. Is there a certain order to the welds on mitered pieces? Outside seam first then inside seam, top then bottom?Last edited by chopnhack; 02-26-2012 at 11:18 PM.AC-180 Lincolnwelder circa '50's
Reply:Hello again chopnhack, I got back to the office and am able to access some additional pictures so here they are. These are related to turnbuckle usage. The way this turnbuckle is set up you could either clamp it onto a particular part or tack weld it depending upon  the application. Best regards, Allan Attached Imagesaevald
Reply:Nothing fancy with turnbuckles.  Just tack in and use then tear them out afterwards.  Big turnbuckles like this regularly show up at Princess Auto.  Its a import/industrial suplus store...  I am sure there is something similar below the 49th..... or make friends with a lineman :')) Attached ImagesLast edited by lotechman; 02-27-2012 at 10:54 AM.
Reply:Originally Posted by chopnhackAwesome guys, I didn't realize how much the jigging is like woodworking. I was concerned because of the movement of the steel with the heat of welding. But I think I got an idea now! Thanks Bistineau, if you weld the top seam, doesn't the bottom spread open? I was thinking of tacking everywhere first, making the last squaring adjustment and then doing the full weld. Is there a certain order to the welds on mitered pieces? Outside seam first then inside seam, top then bottom?
Reply:Thanks guys, the pictures really help to clear things up. I think tomorrow I may attempt a small scale test before the larger project.AC-180 Lincolnwelder circa '50's
Reply:Put a piece of 3/4" plywood down on saw horses- beats working on the ground.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:[QUOTE=chopnhack;855261]Bistineau, if you weld the top seam, doesn't the bottom spread open? I was thinking of tacking everywhere first, making the last squaring adjustment and then doing the full weld. /QUOTE]Not if it's clamped up tight, that's why I prefer the 1/4" angle for this. Tacking top and bottom side first won't hurt a thing. Just leave all the clamps in place until you get 3 sides on each corner welded in, then weld inside corners.
Reply:Thanks for clearing that up bro. That sounds like a winner. Will try out later.AC-180 Lincolnwelder circa '50's