I played with my new welder tonight and was able to perfectly butt weld 22gauge that I had seperated with a cut off wheel(ie a 3/16"gap). The only way I could do this was with .025 solid wire, the .030 wouldn't do it, and I had to also reverse the polarity on the welder. The bead is taller and not as flat with the reverse polarity but it builds great and never blows thru the steel! When I think about it, a butt weld that has a backing welded in behind it is not a TRUE butt weld but a double lap joint, and we all know that a lap joint will rust out in a matter of time, however a butt weld that is treated on both sides after it is welded is almost as rustproof as a new car.IMO ;)

What brand welder do you have? Are you using gas ?
I assume that you were using the .030 flux core wire without gas and the .025 GMAW wire with Argon/C02 gas which was why you had to switch polarity ? What settings did you use for this butt weld ? Thanks for any info as I will be some of this soon. graemlins/waving.gif

Texas,
I am using a Lincoln SP135 PLUS but I think you could try this with any mig. I am using argon/CO2 mix and solid wire for everything. The only time I use flux wire is when it is too windy outside at work for gas and I hate using the dirty stuff. THe .025 wire is just good old mild steel Lincoln L-56 wire and the .030 was some ESAB easygrind. I got the idea of switching the poarity ie.. gun wire to the neg. terminal and work or ground clamp to the poss. right out of the owners manual recomendation for welding thin sheet steel. We use reverse polarity to weld thin stainless and Alu. at work (with the TIG) when we are burning through too much and I have read in several welding books that you can do this with any welder MIG or TIG. But like I said you will have a little more grinding to do since it builds slightly higher. graemlins/beers.gif

3/16 gap---wow! that's a huge void to fill considering the 22guage thickness, good job

If you want a smaller gap to butt weld, use an air saw with their fine tooth blade. You can screw your patch panel onto the car, then follow the edge of the patch panel with your air saw blade and after you cut about 6 inches, push the new panel in so it is level with the car, and tack weld it. The air saw blade width is just right in my experience for a nice butt weld. But if you don't have an air saw, you can do it with the cut off wheel too.