Ok, I will admit that I am new to bodywork and the rebuilding game. I have a 78 F-250 that needs new panels on the box and cab corners. After I get the old ones cut out and the new ones prepped, what type of welding needs to happen to get the panels glued back together? I am a welder by trade, but all we do is heavy industrial stuff. I have no idea what 16-20 gauge needs. thx for the input.

 

I use a spot welder to tack . & a 110 wire welder with .023 wire,, & stitch...Cooling with air every 1/2 inch or so....

 

How long are your stitches? half inch? I seen a few guys that literally tack the whole thing and never run a bead. that .023 wire you run, how many amps? You have it running pretty cold? I don't want to get the sheetmetal too hot and warp it.

 

NOOO! Don't use a 1/2 inch stitch. This will produce way too much heat and warp the metal. For a real weldor like yourself, you will find this to be quite a different world.

What you need to do is lay down a series of very small tacks. Don't let the puddle grow very wet at all. Just let it puddle just enough for a small, penetrating tack. Also rather than jump along with these tacks around the panel that you are welding in place, leap frog around A LOT so as not to build heat in any one spot. A set up as Action suggests will work fine, but I use .035 ES70S6 and 75/25 Argon/CO2. Do NOT try doing this with flux core. The advantage to the gas is the fact that you can weld over weld with no slag.

You also can take some of your kids modeling clay or silly putty and build a heat dam so that the heat does not migrate to other parts of the panel being repaired.

Now for the pattern of these tack welds. Lets just say you were welding in a rectangle. You would get it in position and put a tack in the middle of each of the four edges. THEN, put a tack at each corner. THEN go back and put a tack halfway between the middle tacks and the corner tacks. THEN put tacks halfway between each of these tacks and so on until you have weld everywhere. By leap frogging around like this, you will prevent warping. Do not start your tacks around the perimeter. Do it in a criss cross as I tried to describe.

I do a good bit of repair welding on fork trucks and find that sticking stuff together with heavy 7018 with a DC stick welder to be much easier than welding sheet metal with a wire welder. The key is in setting up the MIG welder. Don't listen to the people that say that it should sound like bacon frying. That's stick welding. With a MIG, it is more of a steady, zipper sound. An experienced weldor like yourself will have a MIG set up on scrap metal and making beautiful stitches in no time.

BTW, a MIG welder is not constant current (Amps), it is constant voltage. The setting will vary a lot from welder to welder. You have two variables, actually three if you include travel speed. The voltage setting on many welders is really a range, then you have a wire speed and then the travel speed is the third. Don't let this intimidate you, just set up the machine with the recommended settings from the chart inside the welder access door for the gauge metal you are welding and it will be very close. Just experiment on some scrap and you will have it set up in no time.

Good luck,

 

Thanks MB, that sounds a lot more like what I read/watched on TV the other day. I probably had a brain fart and said amp when you are right it is volts. We run hardwire and dual shield MIG at work, along with our numerous rods, so I do know what kind of tacks/ welding that need to be done now. Thanks again.

 

If you have a tig welder you can use it instead of mig. You just need to move as if it was mig. You weld quality will be better than mig, but who's going to see it any way. On a mig welder your distance is the key. So if you have the mig welder set as low as it will go and it's still burning out, back off you tip distance a bit.

You will also find on these lower settings you may need a shad lighter lens in the hood.

 

Its a 90 amp welder tops , I keep clicking the trigger for no more than a 1/2 inch(stitch),, I usually count to ten,cool it with air ,, move on ,,,Patience is the key to no warping.. On larger panels I may move around while the other spot's cool .It ends up completely solid weld in the end...

 

You have the OP confused now,,, A stich is not a continuous trigger for 1/2 Inch,,It is as I said ,count to ten ,pulling the trigger,ten times, or what ever, much less heat than continuous,, you can see it cooling between trigger pulls,


but hey , what do I know.. only been at this for 30 years...

 

Okay, I thought that a 1/2 inch stitch meant a half inch weld. I just know what has worked for me which has been a series of very small tacks all over the place to keep heat from building in any one area.

Unlike you guys, I am NOT a pro weldor although I have done a lot of welding over the last 40 years or so. Since I am not a pro weldor, my terminology may not be at all correct. I am a tech that has to weld a good bit, but mainly heavy maintenance welding.

For many years, I welded sheet metal in the same way that I describe, except did it with a stick and the smallest rod I could get. The difference was that I was cleaning slag all the time, where now with MIG, it's the same thing with no slag. I welded lots and lots of thin stuff before I ever did much heavy welding. Now I can really put things back together with 7018 and have lots of confidence that they will stay together.

My partner and I maintain a fleet of almost 70 fork trucks that are heavily abused and destroyed on a daily basis. We probably spend 20% or more of our time welding the stuff together that the operators destroy. Our Mondays are sort of like being the repair crew after the Saturday Night demolition derby.

 

sounds like my place on monday.....

 

So you are an old guy too......

 

Yep, 58 years young.