Butt welding

USU_Stang · Dec 22, 2004

I have some basic welding skills, a buddy with a MIG welder, a mustang that needs body work, and some free time on my hands. Thus, I need to become a good butt welder (i'm talking about sheet metal here...). I've read some stuff on how to butt weld and I think I've got the idea down, but what is the best way to practice what I would be doing to, say, patch an area of my car? I can butt weld pieces of flat sheet metal together all day but this doesn't quite give me the experience I would like to have before I weld my car...

thanks
--Jason

67vert · Dec 22, 2004

when you weld on sheet metal you want to make small welds. Dont go and lay full length line because you will warp your panels. I would suggest putting a spot every 3/4 of an inch (randomly) then after the metal has cooled down put another spot right next to the previous ones. One of the best ways to practice but welding is trying to do a inside corner. They are usually the hardest to do. If you dont want to buy any books or dont have anyone to show you how to do it, watch trucks on spike tv, sometimes he has welding projects on sheetmetal and you can get a very good idea on what you need to do by watching him.

rbohm · Dec 22, 2004

also learn the technique of hammer welding. this is where you use a hammer, dolly, and torch to smooth out the welds you put down on the sheet metal, while at the same time strengthening the weld area. done right you can hide the seem where you welded the metal together to the point that it would take an expert to see the seam.

68rustang · Dec 22, 2004

I would practice butt welding flat sheetmetal scraps together until you can get a good weld down with warping the hell out of the two pieces. If you say you can already do that I would just take your time and try a section of the car. Experience is a great teacher.

1320stang · Dec 22, 2004

I haven't used them yet, but I got these butt welding metal clamps off Ebay. They have them at Eastwoods, but these are cheaper and the same thing.

68rustang · Dec 22, 2004

1320stang said:
I haven't used them yet, but I got these butt welding metal clamps off Ebay. They have them at Eastwoods, but these are cheaper and the same thing.

You can get the same thing from Harbor Freight for $5 for a pack of eight or something.

The problem with them is that they automatically set a pretty wide gap between the panels you are trying to weld. This makes it quite easy for a beginning welder to melt right through the panels they are welding together.

jmlay71 · Dec 23, 2004

I agree those clamps make for a wide gap. WHat I do is make the patch as tight as possible gap wise, then I grind out a spot for the clamp. This way you have the absolute minimum gap. Also when welding sheet metal us a piece of copper behind what ever you are welding. The copper absorbes some of the heat & the weld will not stick thus keeping blow thru to a min. You can buy a triangle from Eastwood or you can go down to your local home store & get a piece of pipe and hammer it to whatever shape you need, flat or that craze contor.

In short keep tight gaps, clamp a piece of copper behind the weld, make several spot welds at ~ 3/4-1" intervals around the butt. Last but not least weld only clean metal. If you need to sand untill it is shinny first.

Mike

USU_Stang · Dec 24, 2004

jmlay71 said:
I agree those clamps make for a wide gap. WHat I do is make the patch as tight as possible gap wise, then I grind out a spot for the clamp. This way you have the absolute minimum gap. Also when welding sheet metal us a piece of copper behind what ever you are welding. The copper absorbes some of the heat & the weld will not stick thus keeping blow thru to a min. You can buy a triangle from Eastwood or you can go down to your local home store & get a piece of pipe and hammer it to whatever shape you need, flat or that craze contor.

In short keep tight gaps, clamp a piece of copper behind the weld, make several spot welds at ~ 3/4-1" intervals around the butt. Last but not least weld only clean metal. If you need to sand untill it is shinny first.

Mike

Isn't there weld-thru primer? Is it expensive and/or no good?

WORTH · Dec 24, 2004

USU_Stang said:
Isn't there weld-thru primer? Is it expensive and/or no good?

I've tryed weld threw primer before, it works good AFTER you GRIND IT OFF.

67GTFastback · Dec 24, 2004

rbohm said:
also learn the technique of hammer welding. this is where you use a hammer, dolly, and torch to smooth out the welds you put down on the sheet metal, while at the same time strengthening the weld area. done right you can hide the seem where you welded the metal together to the point that it would take an expert to see the seam.

Can you explain how this is done or know of a how to link? I would love to save myself a tonne of grinding. Thanks.

dans70stang · Dec 25, 2004

Well, I guess I got it easy then. I have already learned welding in my 2nd period class and one thing that I learned on my own( and have become very good at) is arc welding on sheet metal. Of course I would never arc weld on my 70 stang. But 67vert did give very good advise in spot welding your panels and other body parts. In my spare time I have already started building a custom (mini) mustang body for my go-kart. Can't wait to show it.

68rustang · Dec 26, 2004

WORTH said:
I've tryed weld threw primer before, it works good AFTER you GRIND IT OFF.

Been there, done that, completely agree.

Jester67 · May 21, 2005

Sorry posted instead of starting new thread.

Hack · May 22, 2005

WORTH said:
I've tryed weld threw primer before, it works good AFTER you GRIND IT OFF.

Huh, it worked fine for me.
Edit: I should say that there's no reason to use it unless you're welding something that you won't be able to paint once the weld is completed. I believe it's meant to provide some corrosion protection rather than leaving bare metal in those locations.

ashford · May 22, 2005

a good way to get alot of practice is to make something like this.

lost of welding here about 20 hrs worth

txwoody · May 23, 2005

Hack said:
Huh, it worked fine for me.
Edit: I should say that there's no reason to use it unless you're welding something that you won't be able to paint once the weld is completed. I believe it's meant to provide some corrosion protection rather than leaving bare metal in those locations.

Yes it is good stuff and works great. And like you said Hack it is only used in lap welding. like when you are spot welding something back together and you use a very thin coat.

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