I am doing some small 1/4 panel rust repair on my 70 (see post "Small patches for 1/4s). I have fabricated patch panels that are almost an exact fit for the metal I've cut away on the car. So...I've been practicing butt welding on some scrap fender metal, and I can't seem to get the technique right. I have a Lincoln 125 MIG, and I'm using the settings Rainer provided--current=E and wire speed=4.5. I have learned to make good, solid spot welds with good penetration, but when I try to connect them with a bead, the penetration sucks. Maybe I'm going too fast--the bead looks too 'ropy'. I am afraid of warping the metal if I run the bead too slowly. I was thinking instead of just spot welding the whole damn panel into place, i.e. spotting the corners, splitting the difference, etc., etc. until the whole panel is welded into place. Playing with the current/wire speed settings doesn't seem to improve things--Rainer's settings seem dead on.
The Lincoln manual mentions that, for light gauge metals, a 'pushing' weld motion works better than 'pulling' because it results in a cooler weld. I tried this and it didn't seem to make any difference.
Thanks for the help everyone--it sucks having to ask a zillion questions when you're learning something entirely new.

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Tony Nausieda
1970 SS 396-350hp
Frame-off Resto: Just Say No! 4 years and counting...

The biggest problem I had at first was getting the welds all botched up (looking more like droppings than a bead). Found out it was because my hand was bobbing up and down slightly as the wire fed from the mig gun.

Try resting your welding hand's forearm on the other hand for stability. Then try to make a stable, slow pass about 1/2" long. Once you figure out how long to take on a 1/2" pass, you'll have it.

Also, try to watch the seam just in front of the arc rather than watching the arc. It's very easy to get off track if you're concentrating on the arc rather than where it's going. You still have to watch the puddle, but you have to know where you're guiding it.

I'm no expert at this, but usually once I get "warmed up" it goes fairly well.

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TC Member #643
'68 El Camino

If your bead looks ropey you could very well be going to fast. Take some time with a couple scap pieces and vary the wire speed and your welding speed. You can just try welding a bead on a flat piece till you get the feel of it. When the machine is set right you should hear a steady hissing or cracking sound. Somtimes you can put a back up piece behind your weld joint and have better sucess than an open butt joint.

Good luck!

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What wire size are you using? I have found that .023 with a low heat allows you to go slow enough for good penetration without too much heat. That being said, you probably need to spot weld more, welding beads with a mig in sheet metal creates a bunch of heat, no matter how you do it.

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T

It sounds to me like you are going too quickly. The puddle is not properly melting into the 2 pieces of metal.

To help with the heat try an air hose. Hit the weld to cool it as soon as you've done a 1/2" or so weld. I did this along my quarters going about an 1" at a time (unless I was having welding problems) and it worked fine.
I did not weld in spots but started at one end and worked to the other end. This eliminates the possibility of getting a ripple in the metal do to stretching/shrinking between the welds.

Peter

Well, I finished welding the patches tonight. Not a great job, by any means, but they seem solid, and the area isn't structural so I think I'm ok. The first patch was hell. The welds were really not penetrating well, and I ended up grinding away most of what I initially welded. What ended up working the best is spot welding every inch, splitting the difference, and so on, until the entire piece was welded. This was the easiest way I could get penetration. It's a good thing that this isn't a really visible area. On the plus side, the original 1/4s seem so roughly finished from the factory in this area that I don't think the patches will be obvious at all.
This was a bad project to begin welding experience, partially because of the thin metal, and mainly because welding upside down SUCKS! I think I would have done much better if it had been right side up.
I assume there are no major consequences if the penetration wasn't great on these welds. This area doesn't look to be structural.
I will definitely practice more before I weld anything cosmetic on my car. I was going to weld up some trim holes on the Buick tonight but I have put that off until I am more capable.
Thanks for all the advice, guys--

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Tony Nausieda
1970 SS 396-350hp
Frame-off Resto: Just Say No! 4 years and counting...

Peter, starting at one end of the panel and going to the other scares the livin poop out of me! If you pulled this off you are one talented or lucky welder. With your eqipment and your method of cooling the weld, I am sure you are doing just fine, but think about these points. If you are doing a pinch weld by plug welding you could do it, but even then you should "spread the heat around". But if you are butt welding, tacking it across the seam, then spot welding or small (less than a 1/2") while skiping around. And even doing some and then leaving it to work on another part then coming back is recommended to allow for cooling. You will find that the work to get things back in shape after the weld will be greatly reduced. I don't mean to sound like a smart ass, I am just talking to you like we were in a garage discussing a project. http://www.chevelles.com/forum/smile.gif

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T

When you're welding sheetmetal, you will be welding a series of stitch welds rather than a continuous feed. And you want to weld only small sections at a time, no more than an inch in one spot. Then move to another section of your panel and stitch weld another small bead. You want to keep moving around until you eventually tie all the welds together. This helps to minimize warpage.
A stitch weld is done by squeezing and releasing the trigger in increments of one to three seconds depending on metal thickness. Think of it as a series of spot welds all tied together. Hard to describe, easy to learn and teach.

[This message has been edited by Randy Mosier (edited 01-18-2001).]

Randy, I'm pretty sure that's what I did on the panels. I messed up the first one because I tried to weld small beads instead of stitching. The second one came out great because I used that technique.
Well, all the efforts of the past few days have paid off. I POR'd the rear wheelwells with a foam roller, turned out perfect. Now I can get my new 3.73 posi reinstalled. It's great having this thing come together little by little.


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Tony Nausieda
1970 SS 396-350hp
Frame-off Resto: Just Say No! 4 years and counting...

When you get more practice and become more experienced, you'll be able to tell when you're getting close to burning through, and you'll know when to stop to let the metal cool a bit. All it takes is practice, practice, practice.......

I am about to learn to mig weld on a lincoln 125 also. The points made here are good for me. But can you comment on this advise I got from a local welder. He says to turn the pressure on the gas to the maximum the guage will allow. That way, he says, the weld will be cooled by the high blast of gas. What pressure is best for the gas, for welding patch panels on fenders and quarterss?

The purpose of the gas is to shield the welded metal from the oxygen that's in the atmosphere while the metal is in a molten state. I didn't think it was used to cool the metal. I usually weld set my regulator at the pressure that keeps the weld from forming pinholes, about 20 to 50 psi, depending on whether there's any air movement. If welding outside, with a wind blowing, you may need to max out the regulator. Same thing is true if you're welding in a hot building in the middle of summer where there are a lot fans running.

MARTINSR, It's like Randy said. Once I got some practice I found I could stop just before burn through. I went about 1" at a time and then cooled it. It was either start at one end and work to the other or start in the middle and work out. I can never get welding by doing spots to work. I always end up with the metal wrinkling apart between the welds once I have a few beads down.

I find that with the mig, the heat is almost all at the weld right when you are done. Get an air hose on it ASAP and cool it down before the heat travels through the metal into the panel. I spend as much time with the air hose as I did welding. Dave the local body man told me that's what he always does.

I was doing a slight lap weld, not a butt weld. My welder really isn't good enough to butt weld and it's a lot harder to do so I practice welding by doing the lap welds. I cut it down until there was just a slight overlap left. It was full repro quarters that had the top lip so the weld was on the top of the fenders, not the side of the car. I think this is the easiest to do since there is no weld on the side of the car. If the quarter was good, then it hardly requires any work to look good when finished.
Peter