I keep burning through thin metal

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I cut a Mazda Miata in half and I am building a trailer out of the rear of it. I am working with thin sheet metal for the floor pan and I keep burning through it. My MIG only has 4 heat settings. When I use Low 2 there is not enough heat to make a puddle and I just get blobs/balls of metal that don't really have any penetration. I have my wire speed all the way down and I can feel it "pushing" my hand back. If I go to the next highest heat (High 1) I can lay a good weld down but I just burn through the thin stuff. I have tried kicking my gas flow up (tri-mix) but it didn't help. I have had a very very few successful welds by moving much quicker but it is really hard for a novice like me to do. Am I screwed until I get more practice moving quickly or is there something I need to be doing.My $120 Mig - Harbor Freight 151T 220VMy $300 Plasma Cutter - Rattler 40A  110V/220VCurrent project (Miata Trailer):http://www.lightweightmiata.com/trailer/trailer.htm
Reply:With sheet metal or thin gauge metal, you have to tack, tack, tack with it. Until you're fully experienced with how your machine works, this is the best way, then fill in between the gaps. Let it cool, tack, tack, tack more....let it cool, repeat.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Without ever having used one, I'm going to guess it is the HF welder. When I retired I bought the little 110 volt Lincoln weldpac just to have a wire welder. I used it to restore a '71 Chevy pickup for my grandson. Welded new metal in the floorboards, new rocker panels, and some fender work. Also tacked a bunch of 1/4" bolts to it to pull out some dents with a slide hammer. No problems. If I ever buy another wire machine it will have infinite controls and not the stepped controls.
Reply:I use 75/25 mix with .023 wire and stitch weld. But, like MZ said, sometimes I still have to use tacks. Sometimes you run 1/4 inch, sometimes 1 inch...the metal will tell you what to do. It's hard to give any specifics because the quality of the windings and the individual electronic componates will determine the quality and force of the arc. Just make sure the next machine you get has infinate controls...it solves the problem you have with set taps.Last edited by olddad; 02-07-2008 at 10:36 AM.Reason: spellingAnything worth doing is worth doing RIGHT
Reply:Yeah, I figured the infinite controls would help out quite a bit. When I buy my next machine I'll make sure I get one with it. The HF MIG I had was a deal I couldn't refuse. In fact, I figured that if I ever wanted to sell it I would probably  make money on it (used it is still worth more than I paid for it). Thanks guys!Oh, FWIW, we decided that the thin metal we are laying down now will be held on with sheet metal screws instead of welding it on. There's always more than one way to skin a cat .My $120 Mig - Harbor Freight 151T 220VMy $300 Plasma Cutter - Rattler 40A  110V/220VCurrent project (Miata Trailer):http://www.lightweightmiata.com/trailer/
Reply:What size wire are you using?  .023?A 71 cheby has thicker steel in it than a mazda!David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:First off , i am NOT a body man, nor am I a sheet metal worker. But, My friends who did body work told me if you butt the sheet metal together - NO gaps ! they usually lap over the new pieces , so as to not burn through. The tack, tack, tack, that's mentioned ? Absolutely true , in spades  ![SIZE="5"Yardbird"
Reply:I have the Lincoln equivalent of your machine. Has 4 settings, difference is it will weld on the lowest (33 amps I believe) with .035 flux core and it didn't cost much more than the HF. We all know that David. The old '60 Chevy had even thicker than the '71. Techniques are all still the same. I weld the stuff the Mazda is made of with 3/32 6010. Used to repair cracked out corners on Ford pickup beds at the rate of 2-3 per month using the 6010. Had the migs and tigs there, but the 6010 was faster and turned out better. BTW, you never saw that '71 Cheby, but believe me there wasn't much left there to work with when he started on it.The difference between art and craft is the quality of the workmanship. I am an artist.
Reply:Yea, David, it sure does. Those replacement rocker panels from China don't though. They don't fit very well either. Had to scab another set on top of the first set to make them come out and even up with the doors. They weren't any problem to weld though.