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Howdy,Noob here, just learned how to lay a decent looking tig bead, now trying weld a basic table frame out of 14 gauge 2by2 square tube. Is there a sequence of tacking and welding that works reliably? What I do is: I fixture it square, tack it good and hot, and after it cools a bit take it out of clamps and weld it. But no matter what I do, the shrinkage finds ways to screw me. Oh, I should mention that Im using Evolution 14 inch cold cut saw, that doesnt cut terribly square.Thanks a zillion!
Reply:Originally Posted by dreamycrackheadHowdy,Noob here, just learned how to lay a decent looking tig bead, now trying weld a basic table frame out of 14 gauge 2by2 square tube. Is there a sequence of tacking and welding that works reliably? What I do is: I fixture it square, tack it good and hot, and after it cools a bit take it out of clamps and weld it. But no matter what I do, the shrinkage finds ways to screw me. Oh, I should mention that Im using Evolution 14 inch cold cut saw, that doesnt cut terribly square.Thanks a zillion!
Reply:Your problem is the fact that the parts are not square to begin with.....All the clamping in the world won't help.Filling in gaps = bending and twisting.Simple as that....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:There is no set of steps that works everytime. What you are trying to is not impossible, though, despite your saw. Assuming you have done all you can do to true up your saw, and you have a fixture, you should be able to nail it. You should get three tacks on a corner, flip the piece, and get one more tack per corner. Then check it for squareness, and weld the inside corners. The order you weld it up is crucial, but based on each individual pieces' shape and fit. An inside corner weld will tend to close the 90 degree corners, a face weld will cause it to twist, an outside weld will have the least effect, opening the 90. The face welds are usually last. Welding as fast as possible will reduce the warp. Its a race against the clock, you are going to need some amperage to be quick.I used to use a bucket full of wet rags to cool the weld as soon as I got off of it. This works very well, again, you just got to be quick. The only downside is it makes the patina color difficult to remove. Weld a pass, cool it, skip to another corner until complete. I made large frames of small pieces very square in this way.Constant Current Weldor.
Reply:Square tube is one of the most reactive to heat material you can work with. I had to build 200 of these bus shelters. Welding the 4x4 legs to the 4x6 headers, we had 1/8 tolerance at the bottom of the legs. We found it was faster to just weld everything up, before turning them right side up, to heat shrink the legs back into tolerance. Attached ImagesDont pay any attention to meIm just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:Thanks a lot Gentleman, I feel at ease now. It all makes sense. DavidBrown,I like your tip with the rags. The table is nothing critical, so it doesn't matter, but I was told quenching the weld right after finishing would weaken it. Just out of curiosity: if it was smth critical, would I be able to quench the welds, finish the structure square, and bring back the original strength with a rosebud ?Thermal Arc Fabricator 181IDayton 230/140 stickEvolution 14" dry sawafter 12 years of wood work, realized that the best wood working tool is a welder.
Reply:The key with the rag is you really aren't quenching the welds. You are mostly removing heat from the members. What we want is for the material not to hold heat from a previous weld. We are talking about light tubing, not heavy plate, and you really shouldn't be getting the material that hot too far from the welds anyways. The big key here is original heat input. If you weld hot and fast, you put less heat into the material than if you use less amps and go slow. Seems backwards, but that's the way it works.As far as lowering the strength, depends. Typical mild steel isn't all that reactive to quenching. However as you move to stronger or alloy steels, quenching does begin to create problems that may or may not be reversible. If you end up welding high carbon steel and quenching it, you may have it crack on you instantly. Those cracks may be large, or so minute you can't see them. Cracks won't go away if you reheat with a rosebud. "Junk" steel like rebar, bad frames etc may be rerolled or remelt scrap and can often be a mixture of odd alloy steels and may or may not crack when quenched.Now as far as your saw not cutting right, that should be fixable. 1st thing you need to do is mark a piece of steel so you know how it goes in the saw and make a cut so you know what directions are "off". Is it cutting on a slant to one side, or is it cutting at a slight miter? The miter is usually the easiest to fix. It may just mean a fence adjustment. I've seen plenty of tools where the "square" marking are not accurate. The side to side tilt on my wood miter saw is that way. The 90deg mark is off by about 1/64" in 6". Enough that if I have to do perfect cuts for stain trim, I'll waste a few scrap pieces until I get the saw reset to perfectly square.Cutting to the side downward is a bigger issue and harder to fix since most metal saws aren't designed to adjust that way easily. 1st is the blade in good shape? If the blade is worn and has lost teeth or set on one side, the saw will cut easier on the good side and the saw will drift in that direction as it cuts. That's usually a key note to me that my wood blades are going and need to be replaced/sharpened. Assuming a good blade, next thing to look at is shimming the tower. Usually the tower that holds the saw to the base is attached with a couple of screws. It's possible to loosen those screws and insert a thin piece of shim stock under one side and force the saw "off " to correct for cutting at an angle. Note that these bolts also set the alignment with the fence, so once you get the saw shimmed, you may have to reset the fence to square. ( I've seen plenty of saws dropped where the tower shifts to the side slightly and the saw won't cut square the way it did before and the fence or tower then needs to get adjusted to solve that issue. Remember the shim is going to tip the top of the blade away from the shim. So if you are facing the saw, and the blade drifts to the right as you cut down so the bottom is longer than the top, you shim the left side of the tower and that forces the tower over and it will cut the top longer. You can fine tune the distance you shim in two ways. Either add more shim material, possibly of a different thickness to raise the height, or slide the shim out towards the edge more, reducing the amount of shim contact and lessening the height change.Note that this can be a long trial and error process if you tend to be a perfectionist as it's hard to get an exact idea of how much something has changed until it's all cranked down and you do a test cut. Also note that how much you crank the screws can change the cut once shimmed as well as cheap tools may bend and flex as you apply more tension on the screws.Mc Mastercarr, MSC, Graingers and so on all sell thin stainless or brass shim stock in different thicknesses. By "shim" we are talking about thousandths of an inch. In a pinch, a piece of an alum soda can will work for thin stuff, and alum flashing will work for something thicker if need be. You don't need a lot of shim to make a big change..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan |
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发表于 2021-8-31 22:54:53