Mig Welding Techniques

[Restocougar]

Recently started a restoration project that needs a fair amount of sheet metal repair. Years ago I replaced/repaired sheet metal with oxygen acetylene torches. Thoughts were the oxygen acetylene torches were replaced by the mig to reduce distortion. Purchased a Miller mig and have tried some test panel welding. Struggling with both lap and butt welds; distortion, blow through, and so on. Is there any tips, videos, etc... available to help teach mig welding sheet metal. Really would like to mig rather than going back to the torches.

Thanks Tom

[Len]

Tom
Below is a link to a technique that we use on most patch panel repairs it's easy and works great. You get the results of a butt weld without a lot of the problems.

While this is shown on a door bottom it can be use almost anywhere on the car as long as you have a good replacement patch to weld in.



http://www.autobodystore.com/Truckdr30.jpg
The Backing Strip Method (http://www.autobodystore.com/door_rust.htm)

[65Comet]

http://www.jwharris.com/images/twentygauge.pdf

Check out this site. This is a mig welding wire I use for sheet metal. It is meant for sheet metal and allows me to be a better welder than I am. My local welding shop didn't carry it until I asked them to get it.

It says it prevents blow through...but hold a wire in one place long enough and it will blow through but it gives me more time and now I tackle any sheet metal task with more confidence.

g

[Ranchero_65]

I agree with 65Comet, I got the welding shop here to get me a roll and I'm real pleased with the way it works.

[sarchevyman]

Does that wire come in different thickness? Is it to be used with shielding gas or not? Thanks Steve

[John Kelly]

Hi Tom,

If you know how to gas weld, you are ahead already...here is an article that might help. Regardless of welding method, you have to stretch the metal if you want to remove warpage:

http://metalshapers.org/101/jkelly/index.html

John www.ghiaspecialties.com

[65Comet]

The Twenty Gause wire comes in .30 and needs gas...The directions gives recommended welder settings for several different welders.

g

[Restocougar]

Thanks all for the informaton...

Len, When doing the backing strip method once the butt weld is complete what is the process to protect the backing strip metal from rusting.

Thanks Tom

[wes292]

turn your weld temp down.most guys are afraid to do that for fear of not having it strong enough but for sheet metal on most welders i have used,miller,lincoln.etc.lower is better.just my opinion though.

[98frontier]

Also if you look inside the panel on your welder, it gives voltage and wire speed specs for the ga. metal you're welding to. I have a Lincoln Sp135 with a chart in it, and I know for sure Miller's have those charts.
good luck.

[Restocougar]

Len, When doing the backing strip method once the butt weld is complete what is the process to protect the backing strip metal from rusting.

[Len]

Len, When doing the backing strip method once the butt weld is complete what is the process to protect the backing strip metal from rusting.

In order to protect the backing strip you should apply weld thru primer prior to welding and apply primer and sealer to the back side. If you can't get to the back side then you have basically the same situation that you'd have with any other method, bare metal rusting. About the only thing you can do without access to the back is to try to vent the panel so that it dries and doesn't retain moisture.


http://autobodystore.net/Merchant2/graphics/00000001/up789.jpg (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=UP789&Category_Code=WS)
http://autobodystore.net/Merchant2/graphics/00000001/fusor800.jpg (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=FUSSS&Category_Code=JASS)