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This is my first attempt at welding patch panels on a vehicle. I posted some practice welds last week that weren't very impressive. I practiced a little more and went at it on the truck. I read that rounded corners warp less so I did that, on one corner. Attached Images
Reply:The dot welds were a little finicky. Sometimes when I would start it would pop a little or burn through almost instantly and other times it would be just fine. I kept the metal as clean as I could. I'm using .023 wire with 25/75 C02/Argon. The patch panel is 16 gauge and the sheet metal on the truck is 18 gauge.-Destin Attached Images
Reply:That big gap will probably give you fits. With sheetmetal, the tighter fit the better. Lap joints will make the welds easier since you have 2x the metal to burn thru and the full thickness at the joint, but then you have that open area on the back that tends to collect crud and start the process all over.Edit: Ok I see you are just spotting the welds rather than running beads. You need to go back and fill all those holes however..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:A trick I like to use is to cut out a 1/2" to 3/4" wide "backing strip" to go behind the panel, creating a 1/4" lip all around the panel opening. Drill a couple 1/4" holes around the opening in the panel first and use them to "spot weld" the backing strip in place. Then you don't need the clamps, you can press lightly on the patch to line it up perfect with the panel. Plus, the backing strip holds the weld up and adds mass to collect heat and minimize distortion of the panel. I cut the patch to have a little more than a 1/16" gap all around. It's a little more tedious doing it this way, but when I'm done and sand down the weld I usually don'r need to add any body filler to smooth it out.
Reply:Originally Posted by markfugaA trick I like to use is to cut out a 1/2" to 3/4" wide "backing strip" to go behind the panel, creating a 1/4" lip all around the panel opening. Drill a couple 1/4" holes around the opening in the panel first and use them to "spot weld" the backing strip in place. Then you don't need the clamps, you can press lightly on the patch to line it up perfect with the panel. Plus, the backing strip holds the weld up and adds mass to collect heat and minimize distortion of the panel. I cut the patch to have a little more than a 1/16" gap all around. It's a little more tedious doing it this way, but when I'm done and sand down the weld I usually don'r need to add any body filler to smooth it out.
Reply:Originally Posted by markfugaPlus, the backing strip holds the weld up and adds mass to collect heat and minimize distortion of the panel.
Reply:The key to sheet metal is not allowing the heat to "run out" into the panel. It's easy to fix a dent, darn near impossible to fix a warp that stretches a foot or more across the sheet. Along with the setup technique of a backing strip, the next technique to master is the weld bead. I like to run about 1 inch beads at a time, allowing ample cool down between "stitches" and working all around the panel as I go until I've fully stitched in the patch. There are "heat sink" compounds on the market but I've never tried any: http://www.eastwood.com/ew-anti-heat-compound-1-qt.html
Reply:The main reason that most high-end restorers do butt welds instead of lap joints or backing strips etc, is that the second layer of metal (on the inside of the panel) tends to catch moisture and accelerate the rusting in the seam you have just created. Ideally you want a single layer repair and then coat the backside of the repair with something that will resist moisture ie. POR-15, epoxy primer, etc. If you are making a repair and you don't plan on keeping the vehicle, then the lap type joint will be "good enough", but... somewhere down the road, the buyer is going to be dealing with a rust line under his paint in the shape of your patch.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:Last night I decided to call it quits when I starting having more burn through issues towards the end. I was trying to grind a couple areas down smooth and the sheet metal got very thin in a couple spots. I was getting a little grinder happy trying to make it perfect but I doubt I have the skills now to do that. Is it acceptable to spread a thin amount of Bondo over the patch? I think tomorrow I will weld the outside again and weld the inside also then grind it down. I'll probably do that just for the practice then cut it out and start over again on that section. The seam between the cab and where the hood meets isn't even all the way down.-Destin Attached ImagesLast edited by Sillbeer; 06-20-2011 at 06:20 PM.
Reply:Yes, it is perfectly acceptable to put a skim coat of body filler over that. I dont recommend original Bondo, that **** is junk. However, their gold and professional line are a little nicer to work with. Original bondo mixes pink, gold mixes yellow, and professional mixes green.You may find that once you have a series of tacks holding your patch in place, like your first picture where they are ground down, it is easier to tack the rest by building off the existing tacks.Thermal Arc 210Thermal Arc 95SLincoln Weld Pak 100
Reply:Sheet metal work is so much fun I always butt weld, best way... but man it is challenging.Great call on the round corner, superior for many reasons.
Reply:Get you a welding spoon (or a block of copper) to hold behind and just butt the joints. Weld wont stick to the copper and it will act as a heat sink for you too.http://www.harborfreight.com/welding-spoon-66785.htmlMiller 250x & Lincoln V205-TSmith Oxy-Prop torch |
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发表于 2021-8-31 23:36:36