Thin stainless - mig or tig?

[kev888]

Hi all - thanks very much for this forum and the tutorials, they've really been a big help!

I want to buy a new welder for general DIY use in the workshop. One of the things I know that I'll want to weld is stainless steel in thicknesses down to about 0.6mm - and probably with butt joints sometimes, too. The info on here suggests this thin stuff is really TIG territory, but I notice that some people have managed it with lower powered MIGs - say 25amp or something.

So I was hoping someone could give me some guidance. I'm fairly handy but not an experienced welder by any means, so could I find it difficult to mig weld stainless that thin? Also am I even right in thinking mig would be much cheaper to run than tig?

Many thanks,
Kev

 

[GrahamGKD]

You are correct - MIG is cheaper to run than TIG; it is easier to learn and is a quicker process. I haven't welded 0.6mm stainless myself - if I had some I would give it a go but I've only got 1.2mm 304 sheet knocking around. It would help a lot if the welding you have in mind would allow you to have a piece of copper at the back while welding (that would be my preference with MIG or TIG)? Also, how tidy does the finished job need to look - if it's not too fussy you could maybe use MIG with the thin metal technique (see the tutorials on this site) and dress it up with a flap disk afterwards?

 

[kev888]

Thanks very much, Graham, thats most helpful!

It sounds like MIG may be better for my needs in most ways then, so its really just judging if it will do the thin stainless or not. I would pay for tig if I'm likely to be more successful with it there, but otherwise if mig is easier to learn and cheaper to run..

I'm welding some thin tanks/stock-pots for homebrewing so the weld quality needs to be reasonable, but I can get to both sides so I could grind it back if necessary. Maybe if I curved some copper to a similar radius as the pot I could fit it to the back.

Thanks again,
Kev

 

[GrahamGKD]

Hmm, if it is vessels to contain fluid then the weld needs to be pretty good - maybe TIG would be best?

See what others say later. Have a look at some of the threads started by TIG Paul - he does that kind of stuff.

Incidentally, could you make life a bit easier and use slightly thicker material if needs be? ...or are you repairing / modifying existing tanks?

 

[bert]

Is it something you have to do a lot of? If its not then it may be worth getting them tigged up by someone else saving you investing in a TIG and everything that does with it.

 

[kev888]

Thanks once again, chaps! Unfortunately I'm tinkering with existing stock pots - they're cheap but not exactly heavy weight. I'll have a look at TIG Paul's stuff - should be interesting.

Yep, it had crossed my mind that DIY isn't very economic in this case, but I'm quite keen to learn a new/more skill along the way. I've also had enough frustration with my cheapo stick welder so 'some' sort of upgrade is needed, really.

Thanks again,
Kev

 

[Shox Dr]

You could buy some pots and a well spec'd MIG for less than a TIG setup.

0.9mm SS is bad enough to weld, never mind 0.6mm by someone with none or little experience. Not only that, you would need to shield the inside of the weld (Pot), to stop sugaring (oxidisation) and to get full penetration, so the pot is usable.

 

[kev888]

Yes TIG welders do seem quite costly, but as you say thin metal is also difficult.. From what I can find, the lower powered migs seem to be rated down to 0.8mm, which concerns me a bit for 0.6mm stuff - I'd prefer a mig but if it makes it easier I'd probably be prepared to buy a lower-end TIG.

Don't worry; I realise I'm not likely to make a good job of things, especially to start with. But part of the satisfaction for me in DIY is learning to do new things, so its partly an investment in that too, really. If nothing else it should make some photos for people to laugh at..

Cheers
Kev

 

[Shox Dr]

MIG would be no good for making pots for brewing/cooking. The welds are not very pleasing esp' at that sort of thickness, that's why I suggested buying them. Not only that, a pot needs to be water tight, something you will find almost impossible with a mig, on .6mm

 

[kev888]

Excellent - thats exactly the sort of thing I need to know, many thanks! The last thing I want to do is buy something thats not really up to the job, it sounds like I'll need 'all' the help I can get.

I'm going to design and build something that you can't get ready made - if I can manage it, anyway. I'll be starting with some 100L stock pots, but there'll be a fair amount of customising needed.

Probably I'll just blow holes through them and end up taking them to a pro, but I'll never know until I give myself a chance. I've spent years using costly skin/deck fittings and mechanical flanges instead of just welding on a nipple.

Thanks again,
Kev

 

[Drains]

Kev, thin stainless like that is almost unweldable as it expands So much with heat. Joints have to be dead tight even to get tacks on, then the material will warp terribly on cooling. The more weld you need, the worse it'll be. Anything you can do to design out the weld will be worthwhile.

I'm not trying to put a downer on what you want to do, but I'd avoid that job like the plague!

 

[kev888]

Oops, sorry I missed your reply - I hadn't noticed that we'd spread onto a page two!

Ah, that sounds 'worrying' - there's nothing like in at the deep end!

Oh well i guess time will tell if I can do it or not - I'm really doing this to learn how to weld; it would be very useful to be able to weld the thin tanks as part of that, but if not I can always come up with a plan B for them. Hopefully I'll at least manage to weld on nipples and stuff but we'll see.

Thanks to all the help and info on here, I'm happy to report that I have taken the plunge and bought an R-tech 200amp DC TIG machine - it makes me realise how naff my old stick welder was. I need to sort out a socket for it, I'm thinking a 32amp commando as the welder requires 22amp, and then I'll see how far the learning curve is going to be.

Rest assured I won't be going anywhere near my stanless pots or anything even vaguely thin until/unless I think I'm up to it. Could take some time, by the sounds of it..

Cheers
Kev