welding table bowed top, help

[72Camaro]

I’ve got a heavy welding/general purpose table that has a bowed top. It’s a 5/8 5x5 top with 2x4x1/4 frame and 4x4x1/4 legs. The top is warped up, and I need it flat. I have a piece of 2x4x1/4 that I can add diagonally underneath, or I can get I-beak if that’s better.

My plan is to place the material under the top, weld it to the legs, build a hot fire on top and hope it works itself flat. If that doesn’t work, then I’ll use mechanical force while it’s hot.

Thoughts?

 

[metalmagpie]

You don't mention how far it is from flat. 1/16" or less, you can tack strongbacks to the bottom. Probably 1/4x2" ******** edge. If it's worse than 1/16" you can try straightening with a big hydraulic press or even put it up on 2x4s at two edges and drive your truck over it. Or build a very flat framework and pull your plate down to it and tack it.

It is also possible to straighten plate with flame. But you have to know what you're doing. Search for "flame straightening".

Call your local steel vendor. They get plate steel in big rolls and straighten after unrolling. Maybe they will straighten your piece, or maybe they will sell you an extra-straight piece.

Structural steel is manufactured with generous tolerances. By no means is it precision material. My welding table top is 8" thick cast iron that was planed flat. It used to be a planer table. Side benefit is tee slots and 1.000" holes for fixturing with pins.

You can do good fitting on a warped table. In the end, it's the craftsman not the tools.

metalmagpie

 

[ez-duzit]

...My plan is to...build a hot fire on top and hope it works itself flat...

Come on! Forgetaboutit.

If the top is welded to the frame that's probably where the warp came from.

 

[72Camaro]

Not sure how far out, it’s enough that what I’m building takes a lot longer to square joints, maybe 1/4 inch from center to edges, but that’s a WAG. It was like this when it was given to me, had I built it, it would’ve had a center brace to prevent the warping.

 

[bczygan]

Flame straightening and Blanchard grinding.

Bill

 

[TurnipTruck]

I once had a 4x10 piece of 1” with a 3” bow in it from something really heavy. We left it upside down for 5 years. Now it’s flat. We were planning on blocking it up and parking a truck or a bobcat on it to flatten, but now we don’t have to.

 

[nadogail]

I once had a 4x10 piece of 1” with a 3” bow in it from something really heavy. We left it upside down for 5 years. Now it’s flat. We were planning on blocking it up and parking a truck or a bobcat on it to flatten, but now we don’t have to.

Time & Gravity at work.

In my college class on Geology a student asked "How long did it take to make the Grand Canyon?"

The correct answer is, We don't know, the Colorado River is not done yet.

 

[NUTTSGT]

I have no idea if it would work but I think I would try to draw it back down.

I'd put some bracing under underneath like an inverted "T" across the bracing. Using a large bolt and several nuts, something like 3/4" seeing how your top is 5/8".

It would something similar to a leveling leg for a workbench. The base would be welding to the under side of the table top and the nut welded to the inverted T. You'd need a set of double nuts to make the adjustment.

It'd probably take a spacer between the inverted T and the nut welded to it to allow the double nuts to turn.

Like I said, I don't know if it would work and it's kind of hard to explain in words across the 'net.

 

[gorilla]

I would run some heavy weld beads on the raised up area and then cool it with a water hose to shrink out the bulge. Not much work or risk trying this you will just need to grind the weld bead off when your done.

 

[matt_i]

I'd use the idea of I-beam or heavy flat bar under it, put a small piece of round stock in the center and then pull down between the flat and the cross-beam with threaded rods by tightening up nuts. A "caul" in woodworking.

Once you have it where you want it, you can weld some ribs like flat bar -on edge- to hold it in that position.

Need to know how far its out and is it a flower shape where all 4 corners are up, or is it more of a trough with a single long axis. Just messing around with a straightedge and laying it all over everywhere and noting the results (survey) you should be able to get an idea.

 

[Jackfre]

I'd run the metal cross bracing. Drop a leg in the center with some 3/4" all thread and lift the center. Before I did anything to it I'd find out how far out it is.

 

[matt_i]

I'd run the metal cross bracing. Drop a leg in the center with some 3/4" all thread and lift the center. Before I did anything to it I'd find out how far out it is.

I like that idea better than mine if the plate is a flower shape because it could be done in an "X" pattern with a big threaded hub in center, I'd use 3/4-16 and a Grade 5 bolt or B7 threaded rod. Tweak until you like what you have and then start welding tabs to that X-frame.

 

[brownbagg]

be cheaper and quicker jut to buy a new top

 

[BD1]

You could try welding a bolt or bolts to underside of top , cut hole in angle that extends beyond top, slide onto bolt and draw down with nut or nuts. You may have to cut top free for movement.
Or remove top, turn over , and clamp and tack. Use nuts and bolts to hold top instead of welding.

 

[72Camaro]

I'd use the idea of I-beam or heavy flat bar under it, put a small piece of round stock in the center and then pull down between the flat and the cross-beam with threaded rods by tightening up nuts. A "caul" in woodworking.

Once you have it where you want it, you can weld some ribs like flat bar -on edge- to hold it in that position.

Need to know how far its out and is it a flower shape where all 4 corners are up, or is it more of a trough with a single long axis. Just messing around with a straightedge and laying it all over everywhere and noting the results (survey) you should be able to get an idea.

It’s like a wilted flower, lol, the corners are down. Running a straight edge along the perimeter edges they are flat, running a straight edge across the middle reveals a jump in the middle of the plate.

Taking notes from some of the posts here, I think I’m going to weld in a 8 inch I-beam under the plate to the legs. I’ll weld a few bolts to the bottom of the table and use them to draw the top down with a fire built on the top. Once it’s drawn flat, I’ll run some beads to keep it down.

 

[sberry]

Unless they welded the snot out of it it's highly unlikely that's what put the bow in it.

 

[1MtnGoat]

Not sure you need a fire on top. The "bottom/base" of a fire is not very hot. Try the bolts first. Use a good grade and large diameter so you don't strip the threads. I jacked mine straight with some 7/8 acme threaded rod and pinned nuts.

 

[couch67]

Do you have torches? A rosebud tip and heating in several places should pull it straight or get it closer. When the top is heated red hot, after cooling it 'shrinks' the top side of the table, pulling it down. Disclaimer I have done this with square tubing with success but not plate - but after some reading, flame straightening plate is a proven method.

I might have missed how big the warp is, but it sounds like the table has a crown in the center, so you would heat the top. I'd take some baseline measurements in several places, then try heating in the center first, and see what that does for you.

 

[SGKent]

one needs to counter the force that bowed it. It might be easier to cut the top around the frame and weld a top on, depending how straight you need it. If the metal on the top is unevenly hardened you may get waves in it trying to pull it back down.

 

[HotrodHR]

Pictures?