Thin metal welding tricks

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71340Duster

71340Duster

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I am welding patch panels in my inner fenders. The patch gets thin in the bottom section and while I'm not having trouble sticking it to the frame rail lip I am blowing small holes in the gap (only 2 so far). I've read here where putting copper behind the work helps, my question is is it a thin sheet, wrapped over a body dolly say? Does the weld ever go through and attach the copper to the back side of the weld? Also I read about placing a nail head in the hole and welding it and grinding off the back side. Is there any type of nail to get or avoid? Sorry for all the weird questions here, new welder. My welder is a 110 v mig, wire .023 mixed gas and I have it on the lowest heat.
 
Go to the hardware store and buy a $ .49 copper sleeve for 1/2" pipe and smash it flat in a vise or with a bfh. Hold it behind your weld and you will be good to go. Setup is everything, you should be able to weld real thin with .023, most of the sheet metal I have done is with .030. Don't try to run beads just a series of tack welds is all you are after. Stitch the panel in every inch or so and let areas cool, go back and stitch in between your previous stitches until you are done. Then grind her smooth
 
You can use brass (what I use) or copper, either of them work fine. I have a couple different sizes of round brass stock, I hold the end of it behind the hole while welding, (if possible of course).

Nail head can and will work, STAY AWAY from galvanized, it will emit a noxious gas that is not good for you.
 
I bought this guy at Horrible Fake Tools for about 5 bucks. Works great..
 

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Might smear a little Nozzle Dip on the plate just for the hell of it....
 
Here's a 1/2" example, have also used 3/4" sleeves just depends on how tight the area is you need to back...
 

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I'll have to give that a try myself, I've also had problems burning holes when trying to weld sheetmetal.
What is it about the copper backing that makes it work? Is it just a heat sink that weld won't stick to that makes the difference?
 
Oaktree said:
I'll have to give that a try myself, I've also had problems burning holes when trying to weld sheetmetal.
What is it about the copper backing that makes it work? Is it just a heat sink that weld won't stick to that makes the difference?
Click to expand...

Being non-ferrous (dis-similar metals). Aluminum and brass are also likely candidates but the aluminum melts at such low temps that the "shoe" gets damaged easily.
 
Both copper and aluminum conduct heat WAAAAYYYYY faster than steel. But any bulk back there, even steel, would conduct heat. And of course you don't want it to stick.
 
Copper backer works fine on steel and aluminum welding jobs have used it for both myself. Handy little pieces to have around the shop
 
It is also handy to have a bucket of cool water on hand with a rag soaking in it. When I get done with a TAC or stitch, I'll hit it with the cool wet rag. I believe it stops some warpage in the panel. It gets a little messy on the floor , but worth it.
 
An auto darkening shield can throw the welder off sometimes.

On some jobs when repetitive tacks welds are used to make a continuous bead, a standard shield can allow you to watch the heat dissipate as the red turns to black then hit the trigger again.

It helps me to focus my eyes, and they are not continually dilating with the auto shield going from dark to full light.

My sons find this technique difficult but with practice it might suit you.
 
Dana said:
It is also handy to have a bucket of cool water on hand with a rag soaking in it. When I get done with a TAC or stitch, I'll hit it with the cool wet rag. I believe it stops some warpage in the panel. It gets a little messy on the floor , but worth it.
Click to expand...

Air nozzle also helps, can usually put 2-3 tacks in a row and give them a shot with the nozzle and move on. Takes time, but it will keep your quarters from looking like a ruffles potato chip
 
an a dvantage to using .023 wire is it is designed to work with low heat and wire speed. .030 works o k if the sheetmetal is new and not rusted to half it original thickness! and if you are decent welder! a good welder can fill that small pin hole with .023 IF he uses short bursts, let it cool enough before the next burst of weld. takes a little practice and feel., not that easy to do on thin, rusty, dirty metal, but mig likes good metal TOO!
 
Thanks to all for the responses, good info. I was able to find this copper sheet in town....which can be a challenge on the island. I'll wrap it around a body dolly and build a stand to position it as the backside of the inner fender is clear.
 

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Something that thin I think I would double over and screw it to a nice wooden handle shaped to your preference.
 
I have to weld the trim holes from the rocker molding on the cuda. have about a foot long piece of 1/2 inch copper pipe left over. I just plan on flattening one end and then I will have a built in handle. I am also going to try the nail head trick on the larger holes.
 
try welding rusty exhaust header runners, that stuff is paper thin to begin with. I found using some copper tubing inside the runner as a support was the only way I could join them with an gastight seal. Lots of blow throughs otherwise, even on the lightest setting.
 
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