The Stovebolt Site Forums The Shop Area Paint and Body Shop Sheet metal welding

I am getting close to actually welding in floor pans and rocker panels. I've been practicing on some scrap sheet metal, and its going pretty well. However, I am still having a little trouble welding a joint. I can lay a decent bead on a solid surface, but if there is more than a hair gap between the pieces I burn through consistently, almost instantly. Heres my questions:

1. How tight a fit does it need to be between the patch and the cab?

2. Any tips or techniques for sheet metal?

I am using a Lincoln Weldpac 140, Argon/CO2 mix, .025 wire at level "C" and speed about 1 to 1.5...

Thanks

The fit can a very small gap(hairline) & then use your mig to spot weld it & then short stitches, BUT, skip back & forth on the stitching so you don't warp the metal from too much heat build up. If you are burning through I would turn the heat down & try it. Too much heat will burn right through thin sheet metal...joe

How tight? Butt tight. Experiment until you get the right power and speed. Smash the end of a piece of copper tubing (1/2 or 3/4) and hold it behind, or have someone hold it or clamp it behind the weld. This will keep it from burning thru. It won't stick to copper (or brass). You need to "spot" weld it like Zoo said, you are only welding for 1 1/2 sec, a ZAP is all, till you get the feel and the correct weld. Right now you're too hot or holding too long. Make sure no breeze/wind around and crank the mix pressure up to around 20-25. You can overlap floors if you want to because no one will see it and it won't create a bump in the carpet. But a Butt weld is the pro way. It's pretty hard to cut pieces that fit BUTT tight but that's what you have to do. Turn the tip/wire a little sideways toward the edge of the floor or the patch, this might help not to aim at the crack. MAKE SURE YOU HAVE A FRESH BARE METAL GROUND SPOT CLOSE TO AREA!!!!!!!! If you have not been practicing this type of weld, slice some thin cuts in a scap piece and weld it back up. or use two pieces butted and weld them till you get better and you get the machine dialed in. Bartamos

Make sure the metel is clean and rust free. Some guys just clean up the side they are placing the bead on, but if there is rust on the other side it will blow holes through it as soon as you get an arc.

The bench builders on here will flame me, but I used a metal punch and plug weld the sheet metal. The joint is strong and finish wise for exterior panels it is like a lap weld where you will only need a thin coat of filler to go over the seam and make the panel appear straight and uniform.

Hank

Thanks guys. I think I was just setting to wide a gap to fill. I was cutting slots in some scrap with a cutoff wheel, and trying to weld them closed. When I actually cut out a chunk and clamped it up tight, nothing to it, got a good weld. Lots of good tips above, very helpful as always.

Thanks again!

Actually, most guys using MIG use clamps that hold the two parts in alignment and these clamps hold the gap .040" apart. Then they tack weld the parts together, remove the clamps and finish welding. Yes, skip around running beads about 1 to 2 inches in length.

You might try "pulling" your bead... ie. starting the bead and then pulling the welder away from the bead so you can better see the bead forming rather than pushing the welder over the bead.

Practice before you go to the finish job.

A magnet or two can help to hold smaller pieces as well.

The tighter the gap the easier it is to weld and also the less warpage you will experience. If you can not get full penetration on sheet metal with no to little gap you are welding wrong, turn the weld up heat wise.

IMO those "special" butt weld clamps leave a huge gap, way too big for proper butt welding. The gap left is almost twice as big as the filler rod!!!!

If you need to clamp the panels together and do not have clamps, try this method. Works great giving you a no gap joint with only a few small 1/8 holes to weld shut. Much better then a .040 gap down the entire seem.

http://www.chevelles.com/forums/showthread.php?t=302119&highlight=cleco+butt+weld

When welding with a MIG you do NOT weld in beads. You weld a seem shut with countless superhot tack welds. Also contray to popular belief, a hot weld produces less warpage in the panel. A hot weld takes less time to generate full penetration versus a colder weld taking more time which introduces additional heat causing warpage.

If your "level C" is the third one on the current selection, that is probably a way too much for thin sheet metal. I would suggest starting on the lowest level for first trials.

For as long as I've been on this site, you are the only other person, besides myself, that's ever suggested this. Back in my day that's how we did it and you don't even need a face shield, just wear a welding glove on your left hand, point the wire where you want the tack, cup the tip with your gloved hand, pull the trigger for a second and repeat.
HERE'S a picture of a Plymouth Duster prototype I did back in the early 70s.

Luckily, I moved on to a TIG and never looked back. Did all the welding on my truck with THIS remarkably good TIG machine that only set me back $700... an excellent price for TIG.

For HEAT CONTROL nothing even comes close to a TIG.

As for the cleco method of holding parts together, it works well when parts fit perfectly but sometimes you just need a little extra oomph so I use ALUMINUM BAR STOCK pieces and sheetmetal screws.

Of course, you can always take your time and get some parts to FIT TIGHT and they don't need any clamping.

Didn't see anyone mention this, but I'm on a Weldpak 100HD (110V) and C is WAY too high for 0.25 wire welding sheet metal. I use A and maybe B.

Nevermind, truckernix mentioned it, but I'm pretty darn sure this is your primary problem.

(the 'C' setting that is)

I was using the B range at first, but it was not penetrating at all. Also, the manual said to go with the C range...I will definitely start at A or B when I do it on the cab, I can always go up if needed!

What's your full range? Mine is A-D, so if the range on your mig is, say, A-J, then nevermind about C being low. Try adjusting wire feed speed, too, as well as your drag speed (hand speed).

Also, if your just starting sheet metal welding, expect problems. your going to be welding different gages (replacement panels to original cab), and different alloy compositions (pot metals). Lots of fun!

Just grind the "blade" part of the clamp down to .020-.030. Tape works also. Cool each spot with your shop air. And like I said do da copper trick.