Hello Everyone,
I’m a new subscriber although I’ve been reading this board for some time and appreciate the expertise found here.
I’ve just completed a 4x8 foot welding table. It has a 3/8 steel plate top and a supporting box frame made of 4 inch channel welded to the top 4 inches back from the lip. I used 3 inch square tube welded in the corners of the frame for the legs.
When I turned the table over I discovered the top had a 1/8 inch hump in the center area from rail to rail. Also there is an additional drop of 1/8” in the 4 inches overhanging the frame rails all the way around. I must have warped the top welding the frame and legs to it.
Can anyone help with a procedure to flame straighten or flatten this top?
Thanks, Terry Meyers
It'll be interesting to see the answers that will be offered here. I have a 3X5 table, constructed much the same as yours, and it WAS flat when I built it. From years of welding however, it now also has a curve to it. Not much, but a curve, none-the-less. Good luck. Maybe we'll BOTH learn something!
If the hump is only 1/8" and there is no supporting structure other than the frame, try installing stiffeners on the backside of the table. 1/4" flatbar would probably work fine. You may have to cut some welds and reweld them AFTER you get the top straight. It would only take a few stitch welds to hold this top in place since gravity is doing much of the work.
The edges of the stiffeners need to be straight. You must pull the 3/8" PLate up to the edge of the flatbar.
Flame straightening would work but understand that if something can be flame straightened, it can be flame warped. So if you did straighten this by the controlled application of heat, you would need to reinforce it to prevent heat from welding to distort it.
Placing the stiffeners in a diagonal manner will stiffen the table against rotational disortion but sometimes takes a little more work.
3/8" Plate will probably continue to show areas of distortion as you perform hotwork operations depending upon how much you stiffen it.
Well those are my thogghts
Have a nice day
Gerald Austin
Gerald, thank you for the reply. Once the top is straight I will add stiffeners.
I am a home and farm hobbiest and don't have access to heavy presses so I'm still left with flame straightening the top. One of the members here wrote about straightening steel bulkheads on a ship using heat spots. Could you give me some idea where to start?
Thanks, Terry Meyers
My 3/8" top started to do the same thing when I put it on. As mentioned above, I just did a few stitch welds to hold it on. At nearly 200lbs. it's not going anywhere and doesn't need to have a ton of hot welds to hold it on...more heat, more warp. I also used a ratchet tie-down to pull it into place in one spot and then tacked it down.
I learn a little more with each project that I do. Heat does funny things to metal, whether it's from an abrasive saw or from welding.
Heat a small spot on the highest spot on the convex side. You can allow it to cool naturally or use water. You can then observe the results. The bigger the heating tip, the more BTU's, the faster the metal close to the tip heats up.
Also keep in mind you don't need a "Press". Cut a wedge with a 1" in 6" taper out of 1/2" plate and some dogs. It's difficult to explain so I drew a simple sketch on my site at http://www.weldinginspectionsvcs.com/DogandWedge.htm
The 2nd method shown works best for drawing together tee joints.
Have a good day
Gerald Austin
the idea of flame straightening is to heat up a piece quite rapidly and then cooling it off slightly faster than it would at room temperature. they use spray bottles or a light mist from a hose to cool it off. you don't want to cool it off really fast, because that usually makes things more brittle. anyway, whichever side the heat source is on, the steel will bend away from it when it shrinks. get something like a big propane weed burner to heat up the table.
If it was my table, and I had to straighten it with heat, I would probably start by heating up a small area on the exact opposite side of each weld. If you use a small tip, it could even be the same size as the weld to try to involve the same amount of base metal. See what happens, and if it needs more, just repeat.
I countersunk the holes on the top of the plate and bolted it to the frame. I figured if I beat the top up or warped it too bad, I'd simply bolt on another one. GR suggested what I was going to suggest. Always try to equal out your heat and "most" of the time there is very little straightening to do when your done. Brace it good once it is straight again.
Let us know how it turns out,
John Wright
I'd like to thank all who replied, especially Gerald who posted the drawings.
I'll work on the table over the weekend and let you know how it goes.
Thanks again, Terry
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