How to Prevent Warping When Welding
Viewers ask, "How do you keep the metal from warping?"
If you are trying to weld a 45 degree angle, Kevin recommends a 45 degree metal clamp. The one he uses is from Bessey, a German company. It's good and heavy. Put your metal in the clamp, true it up, and tighten the clamp. Now you are ready to weld.
What do you do if you don't have a clamp or any way to jig up the metal? If you're welding on a metal work table, weld your work TO the table! You don't need much of a tack to do the job. Kevin shows a piece of square tubing and shows that you only need about three or four 1/4" or 3/8" tack welds to hold it. You don't want to weld the whole thing because you'll need to cut those tacks loose. But those little tack welds are enough to make sure your work isn't going anywhere!
Clamping the metal to the workbench doesn't work - you just can't clamp it hard enough. The work wants to move when you put heat to it as you're welding.
If you're starting with a couple of 45 degree angles, whether you cut them on a horizontal bandsaw, a chopsaw or use a framing square and a scribe - not a pencil, chalk or other marker - with a single straight line, you're going to get a nice straight, true cut.
But how are you going to make the upright section of metal from moving? Get a piece of scrap metal, cut two 45 degrees on it, and place it in the elbow of your L-shape. Tack it on each end to keep the metal from warping backward or forward. Now take another piece of scrap and tack it on the outside, top and bottom, perpendicular to your L-shape. Now it can't go side to side, either.
It's time to weld your joint. Weld the four corners and across the top, across both sides. Now your joint is solid and you can cut off the braces, cut off your spot welds, pull the piece off your welding table, and weld the sections you couldn't get to. Everything is now straight and smooth.
The same is true if you're welding plate metal. Spot weld it to your workbench. Put the piece on you want to weld. If it's a leg, for example, you can's just weld the four corners to the plate. It's going to warp; it's going to move. Once again, use your scrap metal as braces at perpendicular angles and weld small tacks to hold it down. Now it can't move as you weld.
Once everything is solid, weld the four corners and each side. Cut your braces and tacks loose, and you're good to go.
What about long welds? If you're butting two pieces of metal together, for instance, and welding them to create a wider plate, you can't start at one end and start welding - it'll warp. Put your plate on your bench, and tack it down. Weld it on both ends, then weld it in the middle. Go about a third of the way, unless it's a really long run, whereupon you'll want to break it up even more.
Tack it on each end, then weld that third. Let it cool. Then get your outside welds, always working in toward the middle. That helps push the heat to the metal, where it's already been welded.
How do you remove the tack welds? Kevin uses Walter Zip Wheel cut off disks. They come in a package. They're thin and take a tiny kerf. They strong and last a long time. Kevin puts one on a 4-1/2" grinder, holds the disk at an angle, and cuts the weld loose. Then he cleans up those little areas where the tack welds were with a grinder.
Unless you want to wait one more moment to see him gracefully handle a square ....
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