Bead too high when MIG butt welding thin sheet.

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I'm spot & stitch butt welding some 20 ga sheet with a Hobart/Miller made AutoArc 130. 75/25 mix with .024 wire. Spots usually look OK, but when filling 1/2 space between the spots often will have a narrow high bead. Technique I'm using is to hold the trigger 1-2 secs, let that spot cool a sec or less, then hit it again just at the edge of the last spot. I can get a line of welds, but the line is high and narrow. The unit has 4 heat settings and I'm using #2. A #1 setting seem to not get enough penetration, and I've had some burn throughs with the 2 setting, so Think #3 would be too high. Trying to be cautious with heat as burn throughs are hard to repair, because it's hard to acces the other side to hold backing. What can I try to get the welds flatter (normal) looking?
Reply:assuming it is at a good setting maybe try pushing it
Reply:Thanks, I'll try that. Been pulling only because it seemed easier to see and hit the backside of the last spot. After measuring the thickness of the metal, it's closer to 18 gauge. BTW, for anyone who might have the same welder, I'm using the wire feed set at 25.Last edited by tottie; 02-21-2012 at 06:19 AM.
Reply:Push will give a flatter bead.  18 gauge should be easy enough to weld if fitup is perfect.  You  have the right gas.More heat for a flatter bead.  This is where a tapped machine is a handicap.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Stick out will change how "hot" a machine runs at a given fixed setting. Hold the torch in close and it will run "hotter" with more penetration, then if you hold the torch  farther away. I typically find newer welders tend to hold a much longer stick out than those with more experience simply because they haven't learned to look into the gun rather than around it.I'd also suggest pushing the bead, and readjusting where you need to be in order to look into the gun rather than standing behind, it which is typical of newer welders.The easiest way to help would be to actually see you weld. Since that not really an option ( youtube vids never show the actual bead during welding as well as seeing it in person), picts are always helpful when trying to make suggestions and corrections. We may see things that you simply don't realize are there that can paint a better picture of the issues you are having.Part of me thinks you should be able to run a bead on the lowest heat setting, going slower, using a push method and keeping a short stick out with good fit up , but that's something I'd have to actually do in person on a few different pieces of scrap to get all the variables right to see if I could make it work. If that failed, then the next thought would be to keep the heat the same or higher, pushing with a tight stick out and try to go faster to reduce total heat input yet get a flatter bead..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:If this isnt something that is too critical and more of a cosmetic thing (auto body panels) Maybe try to fill in your space between tacks with more spot welds. A lot of migs will burn hotter for the initial mig start than during the actual weld. this helps prevent the wire sticking and cold starts to the welds. For spot welds it basically makes your spot sit flat with good penetration while the rest of your weld will end up looking cold. Gun angle will also have a major affect on this
Reply:I'll try some of these suggestions today on some scrap before going back to the floor pan. There are some handicaps. This is a large (18" x 30") stamped floor patch panel on a 74 Karman Ghia, so the access in some areas is not good, especially in back part. It's standing on your head, or under the car which is not quite high enough. Then there's the old eyes, low experience.   Fit is pretty good even though the side and back curve up to meet the original metal. Took days to get an acceptable fit. It is now tacked all around with a good fit. Just need to get the 1/2 to 3/4" spaces between the tacks, and that's the part that needs some improvement. Not a problem cosmetically because most of it will be covered with paint, padding and carpet.One thing I learned that might be useful to other new welders working on something like this. I'm surprised how much you can close up the gap in a butt joint by hitting the spots to the side of the gap. There were 3, curving up, places with gaps more than 1/8", and I had planned to close those up with a bottle jack or some light hammer work. After spot welding the areas around them they closed up more than I expected, and only took a little coaxing. Of course this may not be an option with a totally flat piece, thicker metal, or a curved exterior body panel. A couple of times I even had to use a thin cutoff wheel to relieve a place that had closed up too much, and now would not line up edge to edge. And, cheap 2.25 power, off the rack, reading glasses can be a big help.Last edited by tottie; 02-21-2012 at 11:57 AM.