Butt Welding 18 Gage w/MIG?

-
dartlover

dartlover

Well-Known Member
Joined
Feb 18, 2007
Messages
66
Reaction score
2
Location
Nunya
Can anyone point me to a tech article on welding patch panels?

I'm replacing some floor pan sections in a '65 Dart and I need to make the butt welded seams look good from both sides. So far, it's not going too well :confused:

I'm considering using the copper plate backup method to try and get a better result. Comments, pictures, tutorials, help!

Thank you... dartlover
 
I've never used a backplate, but I know I have to go slow and steady with the right amps so I don't burn through.......Even being really careful with the tack welds, I have always had to grind a little to make the seams look just right........

Maybe someone else can chime in on the backplate or another idea.........:read2:
 
Slow is the key word of the day........
And some practice away from the car.
 
I have figured out the slow and patient part of this already, and I'm not really burning through any longer. But it seems like my tacks are up on the top of the metal and not really filling in the whole gap all the way down to the bottom of the metal. Do I have to tack it and grind it from both sides to fill in the gap completely and get a good cosmetic result?

dartlover
 
I would say, if your weld is on top you either don't have enough penetration so not enough heat or you don't have enough gap between the panels, it should be the better part of 1/16". You definitley don't need backing, I don't even use that when filling trim holes.
 
Low amps and a decent amount of gas, will make for nice Tacks. You will have to grind if you are looking for a nice flat joint though. Its nearly inevitable that you will have some pin holes just because you are tacking and trying not to get the metal hot. My suggestion is that you tack it carefully all the way around. go back and grind it all, then take a light to the back side of the panel to see pin holes. Thats if you are trying to be that picky. At that point be sure to at least wire brush any residue from the area of your pin holes, and tack them again. Im sure you know this but be sure to move around the panel alot with your tack placement.
 
Your biggest hurdle is is heat. The 18g is light so turn down the mig and set it to stitch weld. The problem is that you want to hammer weld everything. And with a cold or sloppy weld it's hard to do. What gauage wire are you using? Check this out: http://www.airgas.com/content/details.aspx?id=7000000000143

Remember be patient and practice on the old scrap.

Hope that helps.
 
Are you using an infinite or a tapped voltage machine? If it's not a infinite setting set up, you may be trapped at a point of a little too hot or a little too cold.

Settings and technique are everything when working on thin stuff.
 
Wow, all great input,

I'm using a Lincoln 140C MIG w/mixed gas. The gas pressure is set at about 18-20. The dials are infinite adjusting and are set to 2 for speed & E.5 for temp. I'm getting good color on the back side so I don't think the issue is heat but I agree it may be gap. I was having trouble bridging across the gap when I had it at 3/16 so I dropped it down to 1/8 (changed cutoff wheels in my angle grinder). I realized that the bigger gap was going to allow me better depth but I kept missing the edge of the metal and shooting the wire past the hole! That's why I thought the copper backer might me a good way to go???

I'll look through the tutorials and give it another whirl.
Thanks again...dartlover

PS: Anybody who knows how to weld live in my neck of the woods, Phoenix Az?
 
WOW, thats a big gap you are trying to fill with no backing plate. Even 1/8 is big, you need practically NO gap. If the the heat is making its way all the way through the panel as you say, then the heat is more than enough to melt the base metal and merge together.

To give you an idea what I am saying, in welding you draw the base material into the weld and just give it filler (which will be your wire). This is how you are supposed to set up your welds. Your base metal should be melting along with your wire to form good "penetration". When you are welding thin metal like that it will burn back when you hit it with the arc, so you want your panels to be right next to each other, so that when it burns back it wont open the gap so far that the wire that melts cant fill it.
I hope that helps more than confuses you. LOL Either way make it NO gap and itll be much easier.
 
here are a couple tips that may help you, wire size needs to be .022 -.025 dia, small gap,about the size of the wire. I like to snip the burnt end off the wire before each weld, it makes for less weld metal in each tac. if the weld is still to big or sticking up to high try less wire speed, also try to lift the trigger before you pull away from the weld . If you pull back and then let go of the trigger you can "pull" the weld out as you move away.. like everyone says ..lots of playing with it untill you get it right...hope this helps ...Ron
 
Try to use .023-.025 wire. It requires less heat. Your gap should not be much wider than the wire you are using. If your gaps are 1/8 (.125) or 3/16 (~.185), you've got roughly 5-8 times too much gap. Get a .045 Norton or .040 Dewalt cutting wheel. Depot has the Norton, Lowes usually Dewalt.

If you are welding outside the CFH setting may be ok. In a stable environment, it may be a bit high. I usually run about 14-16 CFH.

Quick hits. The longer you have the gun activated, the more heat you are transferring, the larger your Heat Affected Zone/Area (HAZ). Usually large HAZ = warping/oil canning. You want to minimize your HAZ.

Voltage usually determines the width of your weld. More voltage, wider bead.

Practice on some scrap piece, like the stuff you cut out if still available. Play with the settings and start with your pieces in the horizontal position to get a feel and settings. It's the easiest position to start with. Once you get that down, turn the piece to the vertical position. Your settings may change slightly.

Generally:
Hissing = too much voltage and/or too little wire speed
Popping = too much wire speed and/or too little voltage

Good luck and have fun learning. It's a blast until you cook something real good. Invest in a welding blanket if you have any seat/foam/door panels nearby. That stuff is not real easy to put out once they get burning... DAMHIK!!! :-D
 
I'll throw in two cents worth here with respect to the original post. I like to use the copper backer trick, especially on thin metal like body panels. It provides an instantaneous heat sink and the weld metal will not stick to it. If you are trying to bridge a gap or fill a hole you can run the bead right across the copper and not burn holes. In theory you could weld a 1/2" hole shut with a backer behind it.

I have several sizes of bar that I have cut and bent into convenient shaped pieces for backing. If you follow the good advice above and try the copper backer as well you will see good results.
 
Lots of good info here from alot of guys that sound like they know welding better than me but I just thought I'd throw in that I, like hydro used a copper plate on the back side and it helped greatly. In most cases I had to have help holding it but that was the greatest obstacle I encountered. You have a tremendous gap to fill so you need something to back it up IMHO.

I found a piece of 1/2" copper water pipe about a foot long smashed flat the last 2-3" of the end and bent at approx a 45 degree angle worked good for most areas. My buddy was able to hold it in areas with no trouble.
 
Excellent input from you all, thank you!

I'm planning on going at it again early in the AM tomorrow. I am determined to arrive at the same results you see on HorsePower, MuscleCar, and Overhaulin even if it takes me a dozen attempts!!!!

I'll report back with pics later,
Thanks again... dartlover
 
Two things that work for me .023 Easy grind wire and using the edge of a cut off wheel to grind just the weld beads, heps keep the heat out of the panel have fun
 
You must log in or register to reply here.
-

Back
Top