Welding 20 gauge to a car body? Having major issues.

admin

A picture is worth a 1000 words. Hard to see now, but the edge where I am welding the body was ground. I tried .030 wire, and 0.023 wire. With all 4 temp settings my cheap mastercraft mig can do, and several wire feed speeds. It's attached and not going anywhere, I can hit it with a hammer. And luckily it will be out of sight, but damn it is some kind of ugly. it's where I am covering a hole into the cargo area of my jeep after I cut the rusted out lower rear quarter out, I had wanted to weld it up nice and tight. But got frustrated and sprayed the outside with undercoat, and filled the inside with expanding foam, so it is sealed up crazy good, but not even close to how I wanted to do it, lol.  How do I do this? I think part of my problem is the body is thicker than 20 gauge. I was trying short zaps, as they seemed to be the most effective, but I started to do longer on the body close to the new sheet and then just a quick zap from the new metal to the weld bead I just left.
Reply:Build up heat on the frame, then quickly drag it into the new panel once you have a puddle going hot on the frame. Stop the weld and do the same thing again, overlapping each spot weld.
Reply:Originally Posted by Jeff000How do I do this? I think part of my problem is the body is thicker than 20 gauge. I was trying short zaps, as they seemed to be the most effective, but I started to do longer on the body close to the new sheet and then just a quick zap from the new metal to the weld bead I just left.
Reply:What DSW said.  Plus the machine you have is not optimal for welding sheet metal.  Without knowing the output voltages of each tap I'd guess even the lowest voltage may be too high.  Also probably don't even know the actual wire speed. It may not go low enough either.   023 will out amperage into the weld.X2 on the auto body class too.  One thing I would love to take at some point. Auto paint class too.Tiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:If your lowest tap is too high, you can back off the distance of the gun to the work and cool down the weld. A lot of body guys do this by moving the nozzle on the gun forward a bit so the tip is recessed an extra 1/8" to 3/16" vs being flush. This allows then to use more stick out and still maintain good gas coverage at the same time.You still have to have good fit up and decent skills however to make this work. It's not a magic cure for having gaps or poor technique..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
Reply:An old timer body worker I worked for in high school kept around some thin copper sheet as a backer. Clamp it on tight and it helps reduce the heat in the joint. Works better with flatter jointsMultimatic 200Ellis 1800Haberle S225 9" cold sawMM 300;  Spoolmate 30A w/ WC-24TB 302GDynasty 280 DX Tigrunner
Reply:As everyone else has said, usually a series of quick tacks is the best course of action with thin stuff, start the arc on the thicker metal and let it wash over to the thinner sheet. Also fit up and metal prep are super important. It is hard to weld to paint, even harder when you have to bridge a gap in the process. The copper trick is nice as well when you can get a piece on the back side, which isnt always a possibility.
Reply:Unless its a Rolls Royce the best way is the easyest. Over lap it and drill and spot weld every inch or so and then cover with some waterproof bondo or kitty hair fiber glass. It will last a long time and you want be mad at your self.
Reply:If you get the machine dialed in, try '' easy grind '' wire. I have read many reviews about it and all good.
Reply:Originally Posted by BD1If you get the machine dialed in, try '' easy grind '' wire. I have read many reviews about it and all good.
Reply:Thanks all! Originally Posted by DSWPractice and lots of it. 20 ga is near the limit of mig and is very difficult for someone with minimal skills. thin sheet is a world all it's own and what works with "heavy" steel isn't the right way to do thin sheet. Lots of fast tacks is usually the way to go, jumping around as much as possible to keep the heat down and cooling the are with a damp rag can also help. You want to stay on the thicker material and wash the spot onto the thinner material coming back and overlapping the previous spots.Also fit up has to be just about perfect. The seam where the two panels meet on yours doesn't look tight enough and that can be a big problem. Many times you need to hold things tight with cleecos, pop rivets or screws, then come back and fill the holes when done to get a really tight fit.It's easier to show than explain and if you really want to learn, taking a night auto body class can be a big help.
Reply:Quote  "Hard to see now, but the edge where I am welding the body was ground."...That metal has to be CLEAN, no boogers of paint, rust or anything that will cause contamination.This modification can be made to a cheap c/clamp vice grip.This is how this section started, After some time and patience it can look like this.  It's all done in 20 gauge.All welds are made with a mig pac 15 with .030 wire and metal match gas on b heat setting and 4.5 wire speed.  You have to use enough heat to make good penetration. Make short tacks and let them cool the move a couple in and make another when it is all tacked, go back and fill it in. Take your time and practice on some scrap first but get it clean.. Good luck.Measure with a micrometre, mark with chalk,  cut with a torch.Never force anything...just get a bigger hammer.RoyOld Airco buzz box approx 1974Lincoln mig pack 15Lincoln 175 square wave1954 9" south bend lathe
Reply:If you're willing to accept small tack welds or spot welds at several places around the patch, dare I suggest that stainless steel pop rivets might be an equally acceptable fix and a whole lot easier.  Yeah, I know it's not as "manly" as a welded patch but it can be just as secure and you'll have to seal it with some sort of "goop" no matter whether you weld or pop rivet.As a matter of fact, if you must have a welded joint, then pop rivets would be an excellent way to force the body and patch together tightly enough so that welding would be easier.And dare I suggest that in this application, gas welding might be much easier if, of course, you have the equipment.
Reply:Are you using a 110v mig/fcaw machine? Its funny, because I was forced to use one on some repairs on my car. Couldnt get it to do anything. Then I learned a few tricks.1 - extension cords are your friend. While this can be dangerous, as 90% arent rated for the load, using an extension cord can reduce total weld amp output. With our lessons in electricity, resistance = heat = power loss. The cord adds resistance to the welder, and can drop your low level amps down enough to be noticeable. Disclaimer - I do not guarantee this as a fix all for low level welding, use at your own risk. If your cord burns up and your garage gets all flamey, it is NOT MY FAULT, nor Welding Web's. With welding, comes safety!2 - copper spoon. Using a copper spoon on thin sheet can be mighty helpful. It can be used to push the panel together for a tack, or as a backer. They are pretty versatile.3 - clean, clean, clean. Sheet metal needs to be pretty clean, in order to weld right. You shoot yourself in the foot if you weld a new patch over old paint, rust, or other issues. Eastwood and other brands sell spray on "encapsulators" that convert and prep surface rust/cancer to a weldable/ paintable surface.4 - weld through primer. You need this for any lap joints you make. Once the metal is heated, it will surface rust to no end. Use weld through primer between the weld joints, and it will be all good. Its more or less a galvanizing spray.Theres more, but its sometimes better to learn on your own, to get the experience, than to just be "told" what to do. Everything suggested here was good advice IMO, from knowledgeble people.Good luck!
Reply:Any ideas if this MIG spot welding kit work?Jeff
Reply:Originally Posted by olcarguyQuote  "Hard to see now, but the edge where I am welding the body was ground."...That metal has to be CLEAN, no boogers of paint, rust or anything that will cause contamination.This modification can be made to a cheap c/clamp vice grip.This is how this section started, After some time and patience it can look like this.  It's all done in 20 gauge.All welds are made with a mig pac 15 with .030 wire and metal match gas on b heat setting and 4.5 wire speed.  You have to use enough heat to make good penetration. Make short tacks and let them cool the move a couple in and make another when it is all tacked, go back and fill it in. Take your time and practice on some scrap first but get it clean.. Good luck.
Reply:I've been doing fill in work at a bodyshop lately, and the welder doesn't get much action anymore... Panels and repairs are getting 'glued' on using a two-part epoxy panel-bond.
Reply:Get a block of copper a backing plate then do the picTiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:Here is another option; flange your panel with a tool like this.http://www.harborfreight.com/air-pun...tool-1110.htmlDrill some holes along the edge of the top panel and plug weld.Doing it this way the flange actually increases panel strength and rigidity, the top layer will fit up nicely to the rest of the metal; so you will have less to grind and fill making your job easier.
Reply:Originally Posted by gmakraHere is another option; flange your panel with a tool like this.http://www.harborfreight.com/air-pun...tool-1110.htmlDrill some holes along the edge of the top panel and plug weld.Doing it this way the flange actually increases panel strength and rigidity, the top layer will fit up nicely to the rest of the metal; so you will have less to grind and fill making your job easier.
Reply:It makes an offset flange so you can lap the seam and "spot" weld it rather than a continuous bead.Teach Ag Mech - Mike At Home:Lincoln Electric AC225Miller Challenger 172Gas AxeWork:eclectic bunch of 90's vintage blue boxes
Reply:Originally Posted by teachagmechIt makes an offset flange so you can lap the seam and "spot" weld it rather than a continuous bead.
Reply:Are you sure you have the polarity set correctly for mig  Good clean ground and check the wire connection to the ground clampCheck contact tip and liner and your feed rollers ...are the feed rollers the right ones for the wire you are usingBacked my CATMA over your CARMA oops clusmy me  What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite  Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:Not all mig machines are created equal when it comes to thin sheet metal. So in this case it's possible that the machine is making it worse as well. Just saying...
Reply:Quite possible peteS....some practice on some coupons of same thickness would be a valuable lesson.Measure with a micrometre, mark with chalk,  cut with a torch.Never force anything...just get a bigger hammer.RoyOld Airco buzz box approx 1974Lincoln mig pack 15Lincoln 175 square wave1954 9" south bend lathe