[BobNovas]

I've been trying to learn how to butt weld 1/8" sheet steel with a MIG torch. 1/8" is close to 10 gauge, which is what thickness I think body sheet is, but being a little thicker should be easier. Besides, it's what I got.

So my question is, how the heck do you make a good butt weld with this stuff? I'm getting a big bump on top of the joint, and only partial penetration (no more than 2/3 the way thru). Any ideas as to how far apart the metal should be, whether the edges should be beveled (and what angle) and what to set the wire feeder and voltage to (miller 175A MIG machine).

[APKhaos]

Hey Bob,
If the body sheetmetal is 1/8" or 10G, we have to guess you are working on a tactical vehicle - something like a Bradley or an Abrams.

Porsche sheet steel is a lot thinner than that - more like 18G or less. I'm no welder, but there are good welders on the board. I suspect that a MIG setup that will give good penetration on an 1/8" plate will burn holes in body panels in a heartbeat.

[cmartin]

I'm no expert, but I've done similar stuff. Try making a small bead on each side of the gap, slowly building up difference. Then, once it's built up you can make it look pretty, joining each side together. Make sure you dont apply too much heat at once, you can burn through thin metal easily.

[BobNovas]

Tony - I had no idea that body sheet metal was that thin. I really thought I was in the ballpark with 1/8", but i can see your point. Maybe I'd be better off with scraps, but I thought I was doing good with bare metal - no paint to mess things up. But now that I think about it, the fender lip is more like 1/16", not 1/8", and I guess that's more the ballpark.

cmartin - I'll give your technique a try. Thanks!

[cmartin]

I spent a few hours last weekend practicing this, went through almost all my gas! The hardest part for me was waiting for the metal to cool, I burned through a lot at first. If you have the heat low enough and take your time, you can close a pretty wide gap, little by little.

[Vicegrip]

Boy you can write a book on welding thin stock.

Most body skins are less that 1/16.

I am a self taught and only a backyard hack but I have stuck some body metal together and had it stay that way for more than a week.

Body metals are thin and warp easily when heated. One way to “butt” is to form a lip and lay one on top of the other then spot weld. This requires more tools than most folks have. The way I have been doing it is to leave a very small even gap using homemade Cleco clamps and then make many, many, many, little spot welds. I use the MiG like a pulse welder and tack the edges together using at first very small spot welds. Bypass the flow valve on the shielding gas and feed low flow but continuously. Once I have the metal edges tacked about every ½ inch or so I go and start filling in-between each tack moving around the seam and getting the metal cool before coming back to an area. I use a damp clean cloth to cool completely and dry with clean compressed air. If you just let the heat dissipate into the metal the metal will expand slightly with each dose of heat and the joint will move. Not might, Will. Use the smallest diameter and lowest temp wire you can. After you have all the welding done finish with a good quality blending wheel. Walter (a German co.) makes real good blending wheels. Blending wheels look like a stack of little sandpaper playing cards fanned out into a neat circle and then bonded to a plastic backing disk. The good blending wheels have a molded in threaded center and can be installed and removed and stay concentric. A hard grinding wheel will most likely just make a mess. A paper based sanding wheel will not knock the joint down without thinning the metal from ether side.

If you can bend the metal edges in some on both sides of the seam most of the added metal will be left after grinding the seam flush. This will require some filler and for the most part not work on compound curves without distorting so you are back to many many little zaps.

Can you spell TiG?

Spend the $ and buy Cleco clamps. You can’t have too many of them. They are handy little buggers that can hold two sheets together from one side. You can also drill holes and pop them in to hold 2 or more sheets overlapping then go back and weld in the holes or install pop rivets.

[matt de maria]

Porsche sheet metal is 20 gauge (.o40") . (Some of the panels for the late small cars run about 24 gauge, because they are tempered. You can't weld these.) For a butt-welded joint space the two pieces about 1/16 apart. Plan for about 20 to 40 amps depending on the circumstances. Do a spot weld about every 2 inches (again depending on the particular situation. This is to keep the panels from warping as you weld. After all this is done full weld between spots but skipp a few inches so the heat buildup is not concentrated.
However if you are welding 1/8 " sheet you will need a lot of amps. The rule of thumb is to start with the current equal to the thickness of the metal. 1/8" = 125 amps for starting out. i would estimate that you will need about 150 to 200 amps. Spacing the initial spot welds applies here too.
You would be much better off in practicing on 20 gauge metal so you can used to the tecniques with this gauge.

[Vicegrip]

Thanks Matt. I didn't know that the later stuff is tempered. When did tempering start or is it only on some stock? The Clecos make the 1/16 gap.

Bob. Call me if you want some Porsche body shop scrap to cut up and put back together. Practice and tune is the best way to get good results. sounds like you want some older 911 stock. Right now I bet we gots lots of bent Ki-ann front ends.

[markwemple]

Most manufacturers today use 20 guage(remember if you are using galvanized to grind off the edge first). Butt welding takes some getting used to. Lapping is stronger and easier. Play with the heat for penetration and remember that if you are using dissimilar thicknesses to focus the heat on the thicker panel.

[jpinkert]

Interesting thread considering that I'm currently learning the art of welding. I have a MIG welder but I've seen what TIG is capable of. For butt welding, it seems that TIG is the most desireable way to join the panels. It can be much more precise...if TIG welders were only affordable.

Does anyone go so far as whipping out a hammer and dolley to shape the metal and finish the joints?