welding

Much better to O/A or TIG it. 120V wire feeds cannot get down to a useable amperage for < 20GA steel. They will just punch the wire through and burn holes in the panel. You won't be able to run a bead. OTOH, at lowest setting (if it has one, that is,) you may be able to plug-weld the panels by drilling a 1/16" hole in the overlap. A quick blip of the trigger and a circular motion of the wire *can* successfully complete the weld, but only if you have the technique and skill down. If you want to but-weld the panels, forget the wire feed. A 00 gas tip and 1/32 rod or TIG works way better here. JR Dweller in the cellar
snipped-for-privacy@hotmail.com wrote:

Use the wire welder much as you would a spot welder. Make a small spot in the middle of one edge. Move an inch or so and repeat. when complete with that edge do the same to another edge. Repeat the process until you have spotted the whole patch. Don't try to make a bead on sheet metal. Chances are you'll burn through and just upset yourself. After you have finished spotting the patch at the one inch intervals, go back and spot the areas in between. Do this until you have filled the edges with spot welds. Once you have done that you can grind (carefully) the welds down flush. It's time consuming as hell but will be worth it if you want a nice patch. I've used this method several times and got nice results. If you're looking for good work you just can't rush it. Make sure that you work opposite sides when doing the spotting to eliminate, or at least minimize, heat buckling. Good luck.
Jim Chandler Apple Valley, CA

Well, here it is. Take some pieces to practice on. Spot weld after spot weld. If you have an autodark, count until the autodark lightens. If you have a regular hood, watch for color or brightness in the puddle, then hit it again. If you time your sequential spot welds correctly, waiting until the moment one cools to do the next, and doing all for the same length of time, you will avoid burn through. I have done this with lots of thicknesses of sheet metal, and it comes out looking like TIG.
Remember, tricks are: Weld for the same amount of time, let cool for the same amount of time. I start the new spot weld on the outer edge of the previous spot, and point the gun towards the outside of the previous spot circle.
Running a continuous puddle on sheet metal will result in burn through 1,000 times out of 1,000. Sequential spot welding is impossible to burn through because you don't build a big enough puddle, and you wait for the last one to cool. As you get good at it, you can increase the heat, and achieve more fusion.
I've achieved water tight joints when making a pan to go under my washing machine. If you miss a place, just put another spot on the pinhole. Remember, don't get it too hot, don't stay too long, and let it cool. You want a hundred spots in a row, not a continuous bead.
HTH
Steve

There are special clamps made for holding sheet metal in aligment, edge to edge. I bought some years ago from Harbor Freight--don't remember details. I also made a few--it's not too hard. Use a strip cut from a body panel. You slip it through the joint and pull from the back and clamp from the front by tightening a nut.

A small 110-volt MIG works really well for such work. In spite of what others have said, it is definitely possible to buttweld 24-gage and even 26-gage steel -- but it does take some practice. A restoration shop near here does it routinely with little 110-volt Linc SP120+ MIG boxes. Forget it with an import box.
Heat distortion is a major issue with O/A, about a non-issue with MIG. The easiest approach for a newby is to use a punch and flange tool, like this: You cut your patch about 1/2" bigger than the area it will fit. Then you flange the patch and punch the body or vice versa. The punch side makes holes about 3/16" dia, while the flange side makes, well, a flange so that the patch ends up flush with the body metal.
Stick the patch in place with some small sheetmetal screws, or with clecos that go thru 1/8" holes and are reusable. Eastwood also sells punch 'n flange tools but they want a fortune for them. The HF tool works fine. There are also hand flangers, but if you don't have air, a DA sander and a high-speed pneumatic rotary sander you are gonna hate bodywork! These tools are cheap; HF stuff works fine for as long as you need them to do a car or three.
Once everything is lined up right and secured in place, go around and fill the punched holes with the MIG. Even the import boxes do this with no problem. I typically used about 1 hole per inch. If you want to, you can go back and weld the seam but it isn't necessary.
Note that I say MIG rather than just "wirefeed". Fluxcore wire runs a bit hot for sheetmetal, and it leaves spatter and flux to clean up. I like AG-25 gas (25% CO2, balance argon). Straight CO2 might be OK too, never tried it.
Pull the cleco's or the sheetmetal screws and weld those holes shut. Very light grinding will flatten the welds. A gob of bondo about the size of a walnut will then fill the crack flat over an entire fender skirt repair. When I helped a guy who'd never done it before, he was able to fit, punch, flange, weld and bondo an entire fender skirt in about an hour and a half.
Bondo is not "bad stuff" if mixed and used correctly. It will fail if applied too thick, applied to dirty metal, or if moisture can get at it from the back side. I've had Bondo last quite a few years.
Check out Ol' Blaze. There was about no original metal on that vehicle below the upper trim. The rustwork "restoration" was done some time before I sold it, and I saw it runnin' around town for a couple of years after that.
If possible, seal the back sides of the joints with body sealer. It isn't always accessible, do what ya can. Even unsealed, these joints can last for many years before rust again becomes an issue. I live in the Minneapolis area, lots of salty slush during winter months.
Rocker panels may not lend themselves well to punch 'n flange. I don't recall how I did those, probably with butt joints stitched in place and then a continuous bead. Contriving a strip of sheetmetal backing behind a joint can make things a lot easier when that's possible, but it has to fit close to do any good.

"Don Foreman" wrote
I got a 220, but for sheet metal, a red or blue 110 will do the trick all day long. AND you can plug them in anywhere.
Steve

Right on. I have a 220 also. They overlap nicely. Bigger blue works really well on anything over .090", the lil' red box rules on the thinner stuff down to 28 gage steel.
The lil' red box and all the rest of the bodywork tools repaid themselves many times over when I was keeping a fleet alive and presentable while launching (educating) 5 kids and not sending a farthing to either Japan or Detroit for 20 years.

I thank you all for the help! I will try your advice it is very much appreciated.