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MG MGB Technical - Welding Advice

Ready to start some bodywork repairs so have got various replacement panels and some 0.7 & 0.9 mm steel sheet.
I also have a second hand 100A mig which currently uses fluxed .8mm welding wire. And have been doing some practice runs.
I'm having mixed results, with either poor penetration or overheat or even blowthrough. I have seen recommendations to use gas as it gives a cleaner weld and also go down to .6mm wire which should work better with the thinner sheet. Any thoughts out there? I used to be pretty good with gas, so do I need lots of practice & fine adjustment to get it just so?

cheers

pat
Pat Gregory

You will have much better control with gas. You can fine tune easier.
darnoc31

I always used gas and kept the current setting fairly low, particularly with thin sheet steel and when doing seams. As you indicate, a bit of practice will determine the best settings for your kit.
Richard Coombs

I tried the gasless wire and didn't have much luck. Using gas worked much better for me. I think the wire is 0.6mm that I use. Now days I am more inclined to weld some things with actual gas, as in Oxy-Acetylene!

One thing to check is the polarity on your welder. It is different between using gas and using gasless fluxed wire. Torch positive with gas and negative when using the gasless stuff.

The one thing you can definitely say about welding is practice certainly helps!

Simon

Simon Jansen

My Mig came with core wire I was doing some poby panel replacements on my son's eclipse and just could not get the unit with the smallest gauge wire to do much more that tack. Each time I tried to fill, it burned through.

Switched to argon/nitrogen mix and the smaller wire and it worked perfectly.

I think flux core may be ok for heavy steel, but not for thinner stuff.
Bruce Cunha

Our local adult education schemes here, called TAFE run a Mig welding course. For all you out there whom have welding experience, would you out of course recommend proper instruction? Or can one learn by trial and error? Mike
J.M. Doust

Pat,
You should not have to worry about polarity on small Mig welders as they are set. Welding thin metal is difficult at the best of time. I found .8 wire the best as it is less likely to snag in the feed harness. also the thinner the metal you are using the more likely you will blow through. I rarely used anything less than 1mm. Dont have the welder set to low as it will not penetrate but use short bursts. Make sure the metal is clean, remove paint and rust. I have been a welder most of my life, recently retired. and many of my workmates could not get the hang of thin metal welding. Practice will help. Trev
Trevor Harvey

I'm with Trevor on this - I never used any metal thinner than 1.0mm. The other thing I would mention is that the most critical setting is the wire feed speed. For thin metal use a low current setting, then play with the feed speed. If it is too low the wire will burn back into the torch. If it is too high the weld becomes too fierce and burns through. When its just right you get a nice frying eggs crackle.

Even so, with thin metal you have to weld in short bursts or it will distort. Oh, and get some CO2/Argon and chuck the gasless wire away, it makes a big difference.
Mike Howlett

I second the remark about cleaning the work of rust, back and front. Rust encourages burn through. Also, you can clamp a sheet of copper or brass to the back of the seam and it will not burn through and the copper will not fuse to the weld.
Art Pearse

One other thing, an auto-darkening helmet makes things a lot easier when you are learning.
They are quite inexpensive these days.
David Overington

I recommend the welding course. My body work is done and the car painted. I did all the welding, rocker covers, rear quarter panels and various small patches with a 110v Clarke Mig welder. I had a buddy help me set the welder up as it came without any directions and I went from there. I am now taking a night school welding program. 10 2 hour lessions. I could have saved myself a lot of time and effort if I had done the welding course in advance. Money saving on welding gas, wire, grinding discs and beer would have paid for the classes. Ok ...the beer would have been consumed regardless.
Kelvin Hawkins

This thread was discussed between 05/12/2011 and 07/12/2011

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