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I've been trying to get my mig dialed in to weld on the floorboards of my cab, but i keep blowing holes in the steel! I Keep adjusting the wire speed and voltage but to no avail. I've tried the recomended settings provided by the welder but it doesn't work. I'm using CO2 as the inert gas. Any problems here or what the heck?! HELP PLEASE!
:confused:

Get some scraps of similar guage to test on before welding on the truck..............you can't weld in one place for too long; you have to keep moving.
I have welded some pretty thin metal with an oxy/acetylene set-up without blow-thru............it can be done.
Remember, Torch angle, torch gap and torch speed are needed for a good weld. Tack it all in place, then skip weld (go a few inches, then move to another area; repeat and return). Weld right on through your "tacks" to insure penetration.
Could be your "amps" are set too high.........too many "volts" and you will have "berries" all over.
Practice on the scraps, get you machine dialed-in, then get yourself "dialed-in"...........get in a comfortable position so that you have freedom of movement all the way through the welding area. Use both hands and move steadily across your work..............
You'll be "stackin' dimes" in no time..........
A good weld looks like a stack of dimes, layed over flat.
THere are a lot of books on this and I am assuming you are not a career welder. If by chance you are, my apologies.........
Need more help? let us know.............
What brand of welder are you using? I hope it's a 220v type............E70S6 is a good wire to use along with a Co2/Argon mix............straight Co2 is fine though.

Get a chunk of 1/4" thick copper to back it up and soak up the heat (maybe a 2" x 4" piece). It works well for filling holes that you've blown through. Also, I had good luck mig welding for 2 or 3 seconds pausing 2 or 3 seconds welding for 2 or 3 seconds, pausing 2 or 3 seconds etc., keeps it from getting too hot and lets the weld solidify.

Let me see if I can make GMC248's excellent response more confusing!

Remember that increasing the wire speed increases the amps, which results in more heat. Increasing the voltage setting, (1,2,3,4, or A,B,C,D) also increases the heat. Conversely, reducing either dial decreases the heat. Moving one adjustment usually requires adjusting the other, too.

When I'm trying to help someone learn to weld, the most glaring thing I find is that someone learning doesn't put in enough tack welds prior to welding the seam, which '248 mentions. Consequently, the 2 edges of the seam are allowed to distort during welding. I recommend tacks about 3/4 inch apart before actually welding a seam. Make sure that the 2 edges are perfectly flush. Any discrepencies in the seam are going to make it difficult to make clean welds. Then, it's easy to stitch the panel together intermittently like described.

MIG weld will tolerate a little gap in your seam, but it should be pretty close... no more than the diameter of your wire.

Unlike '248, I like a 110v machine for sheetmetal work, and I run .023" wire. I find for my welding, that a larger wire requires more heat, meaning potentially more burn throughs, or, a "prouder" weld that requires more grinding. Even if your machine is 220, you should be able to dial it down. Try lighter wire, if you're not already using it.

GMC248 gave the best advice.... practice, practice, practice. Taking care at the front of the job to fit you patch carefully and accurately results in a faster, nicer installation that requires less clean up as an end result.

Tim

Do you have the polarity correct on the welder? If you converted from wirefeed and forgot to reverse the polarity, you will have problems.

It is also very important to get rid of all rust before you weld a seam.

Is there a way to know which way i have the polarity set? I think i may be running too thick of a wire. I'll get some thinner stuff and let ya guys know in a couple of days. Thanks boys!

I found thinner wire key to welding old thin sheetmetal. Brian

Which welder do you have? My Lincoln has big "+" and "-" terminals that the leads connect to. You swap them to switch polarity. Mig welding uses electrode + polarity, and flux core uses electrode -. 0.025" or smaller wire is best for 24-18 gauge mild steel.

I use .025 wire and I USE A 75%/ 25% MIXTURE ARGON/CO2,ALSO MAKE SURE YOU HAVE A GOOD FIT, MOST PROBLEMS , ARE TRYING TO FILL IN LARGE GAPS,TAKE YOUR TIME IN FITTING AND TACK EVERY 1/4 INCH IF YOU HAVE TWO,TRY THIS BELIVE ME WITH PRACTICE YOU WILL DO FINE. OLD NAVY 51............