I'd like to learn to weld for automotive and general use. There are no DIY type courses hereabouts, so I'm going to have to learn from a book or video. I should say I have done some gas welding in the past, but I don't want to go down that path, and the skill needed for arc welding is not something I wish to approach.
I have some understanding of what MIG welding is, but I do not know what TIG is (in fact, I don't even understand what it stands for).
Given my lack of experience and understanding, what are the relative merits of the two approaches please, in terms of cost, finish, and skill level?
=============== Mig welding is generally cheaper than Tig. Have a look at:
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for some idea of relative costs. Arc welding isn't really the best choice for automotive work although an arc welder is much cheaper to buy than a Mig welder. Mig welding can be difficult if you're working outside in windy conditions because the wind can blow the shielding gas away and spoil the weld.
If you buy a Mig welder make sure that you get a 'non-live' torch.
I have a cheap mig welder and an old electric arc welder
I find the mig good for thin metal but have not really mastered it when welding 3mm or thicker don't seem to get sufficient penetration and the wire comes out so fast. Have tried and tried with this I get a better quality weld on thick metal with the electric arc.
Also mig needs a much cleaner surface that arc to work at all
My main problem is butt welding standard thickness car panels - exactly the main sort of use I want it for. Making a neat job of a patch is ok. I also did a bit of work on a garden gate and got good results - although I couldn't say for sure how deep the weld penetrated. But it certainly looks like it did and it's also survived.
Yes - the steel needs to be as clean as you'd have copper pipes for soldering.
As others have said, a MIG is the easiest to use and to get good results with. I would also suggest getting one that is capable of *also* using flux cored wire* - even if you have no intention of using this method to start with. Although lots of people dislike the flux cored stuff, and it does result in a somewhat messier weld, it is easier to use outdoors when it's windy ;) I also find that it gives slightly better results on metal which is not as clean as it might be ;)
*This just means that the welder should be able to swap the polarity of the torch and clamp and that the feeder roller can accept the slightly larger wire. Need to use the matching tip too, of course.
MIG, not TIG Easier to use, more useful, machinery costs 1/3rd
Gibson's "Practical Welding"
Get a Cebora machine from Partco, not a Clarke and definitely not low-end SIP. Murex are nice too, but don't do really low-end ones.
Don't get a no-gas machine. Using flux-core wire has its place, and it can be very useful outdoors in a wind, but it's expensive and your machine should certainly have the _potential_ to be used with gas.
Disposable bottles are OK if you're starting, but they don't store once opened.
Gas should be an argon/CO2 mix and _NOT_ pure CO2 from the pub.
Learn to wire-feed weld with an argon/CO2 mix. Always use it for thicker steel. Once you're good, for _some_ purposes you might like to use CO2 instead. This is not the normal way of working though.
Forget trying to do aluminium with a wire-feed set, unless it's a real one and you invest in some extra kit, like a spool-on gun. It's just not practical with "retail" MIG.
To learn, read the book and do plenty of practice. Get a wheelbarrow of 1/4" plate scraps (not car bodywork) and weld it all into a lump. Turn all the dials up to max and just go for it. As you get better, learn to turn the dials down (read the book again).
Learn about spray transfer mode. If you can, go and use a 400A welding set on 1/2" plate (I spent half a day in a steel-fab factory with the apprentices from my welding NVQ course).
Learn about dip transfer mode. This is what you'll normally be using.
Learn about globular transfer mode. This is what most domestic welders use, which is why their welds are rubbish, This is also why you don't use CO2.
Section your completed welds in half and do nick-break tests on them. Unless you do this and _test_ your welds afterwards, you'll never learn to do it right.
You also need stuff like a 4 1/2" angle grinder, flap wheels, a couple of cut disks, a twisted-knot wire cup brush, hammers, moles, mag clamps, spare fixed-glass helmet for spectators, gloves, boots, kneepads, cotton or nomex overalls, a leather welding jacket (cheap!), bottle of Water-Jel (barbecue sauce for welders).
Then you need tools to cut metal to shape.
Get an automatic helmet.
Practice.
Don't rule out a stick welder. Often cheap, and sometimes useful.
Thing that worries me about these is that you're creating the perfect water or moisture trap. Maybe not a problem if you have good access to the other side and can use seam sealer, though.
If you don't have access to apply seam sealant you can usually use a zinc weld-through primer then spray the back with waxoyl type underseal. I tend not to worry about that sort of detail, but most of my welding is of the "get you through the next MOT" variety :-)
Then I'd simply seam weld a surface patch over the problem. I can do that ok. But if making an *invisible* repair, I'd hope it to last as well as the rest of the car. I've seen far too much 'pro' work where welding in even a new panel results in that panel rusting through in short order due to not being properly protected where it doesn't show - my brother's Stag, for one. Had almost all the panels replaced with new - and pics and receipts to prove - before he got it. And a superb re-spray. But had rust bubbling through at all the usual points some 4 years later - which is why he got it cheap.
Wow! Lots of useful stuff - thanks to everyone for all the replies!
Have ordered one.
Ordered that as well :-).
Not sure what you call a low end SIP? I ordered an ex-demo (but unused) SIP Turbo 130 from eBay, which I'm told is the largest one you can plug into the wall without a special supply. However, since the order, the supplier has written to me and said that the welder is not dual purpose, would I be happy with a normal one? I replied that I don't know the difference, and asked him to explain! Should I reject the order???
If I had a pound for every time I heard/read that. I have used my gas mig outside in reasonable wind without any noticeable degradation of weld quality. I think if it's really windy then there may be a slight advantage in using gasless, but the difference just isn't that big.
I have a SIP 130 amp dual-purpose welder and I have used it both ways, being able to use gas or cored wire can be quite useful so if you can I would try and get a dual-purpose (dual-mode?).
Some people here don't like the SIP welders but mine has worked well for me.
The last test they did - a few years ago - made the SIP Turbo 130 the best buy. Which I did. The wire feed speed is difficult to set for thin sheet. And the gas regulator is both marked and works in the opposite way to those given in the (inadequate) instructions.
I can get good welds when overlapping two sheets of thin steel, and with the thickest I've tried which was about 1/4 inch. But can't do butt welds on thin material - the main reason I bought it.
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