Mig welding shaped metal

[Peter Tommasini]

Hi guys,
I am not trying to start an argument but for close to the last 38 years i have mig welded and oxy welded both chassis work and bodywork.
Now lets start with the mig... excellent for chassis construction and repair
not as good though when attempting to butt weld sheet metal, the reasons being : the time saved in the welding process with with less distortion is then consumed buy the need to to clean up each side of the weld with the grinder, then you need to try to attempt to release the weld and although the distortion has been minimalized you will then need to planish a very hard weld next to a softer material. This will cause a small crater on both sides of the weld, this in itself becomes a nightmare when you attempt to file finish.
This is not a major issue though if are happy to finsh off your repairs with a little bit of bondo
Now oxy welding, none of the above occours except a little more time in tacking the job together and some more distortion at the end
BUT!!!!!!!!!!!!
by planishing and releasing the weld, providing that the panels are equal in shape, this can be for example a mud guard made in two sections, or a lower door skin section, roof skin sections etc
your are then able to planish the weld, release the distortion caused by the weld with much greater ease. Even if you use harder wire than normal for a filler. This happens because the amount of heat in the sheet, even though it creates distortion as mentioned it also anneals the whole area
be it either steel or aluminium in question
I may be wrong,and i am not saying by any means that i am completely right
but it has served me very well over the past four decades

[David Gardiner]

That is what I have been saying Peter, I have been given a lot of stick for it on occasions and people don't seem to understand that because it is possible to weld with mig and that mig machines have been pushed by the manufacturers it does not make it the best method for sheet metal. Gas is my personal favourite method but some prefer tig. For aluminium I only use gas.

David

[Marty Comstock]

this thread was not intended to be a mig vs *your personal favourite welding method*, it was intended to help those having trouble mig welding sheetmetal, for whatever reason they chose to use this method.

If yall like, start another thread on why you'd want to chose one method over another rather than muddying up this one. This thread is (was) intended for people having problems with their mig welding sheet metal.

Marty

[peter d]

Hi marty
I shortened a triumph motorcycle mudguard just cut out a strip about 2 inches wide where it was split and had some extra holes and was going to oxy weld the two good bits back together .Then charlie the boilermaker I worked with said why dont you mig it . He then tacked it in about 4 places and welded right across the guard .In less time then it took to type this. I was very impressed to say the least .No distortion very little grinding to clean up. I presume this was because of his skill and the speed that he was able to weld at. Oh and my friend still has the bike and 25 years later the weld never cracked .

[David Gardiner]

Hi Marty I think it is a good thing if people have as much information as possible.

David

[Marty Comstock]

So feel free to start another thread discussing that exact topic rather than trolling this one. Please!

Mods, can we clean this thread up of off topic discussion, or split it off to start another thread?

I have received many comments from people at meets to start a thread helping folk with their mig welding, I would like to keep this thread clean and on track.

Thank you.

Marty