I tried welding 0.75mm steel sheet for the first time yesterday. Even with a little welder and set to minimum, it is a bit much.

I started off welding 0.5 seconds on and 1 second off and it was still blowing through every couple of centimetres, so I stopped after about 2 cm and welded a bit further along and then came back to the first weld.

The results show enough penetration but a fairly high build up of weld on one side which needs grinding back. The results are strong but not pretty. Are there any more tricks for welding thin stuff?

pot rivet :O)

Some good advice here

Anything below 1mm with a diy type mig is difficult, the minimum setting on these machines is 40 amps, 30 if you're lucky. You really need to be down at 20 - 25 amps.

draw it forward so the wire is going into 'cold' metal rather than backwards. It helps a bit.
maybe use a heatsink too?

Use 0.6mm wire, i found that made welding thin metal much easier

Check out this site I have found it useful in the past.

http://www.mig-welding.co.uk/

can you clamp the join onto a lump of metal to act as a heat sink so the sheet does not get too hot? (aluminium may work as you are unlikelhy to succeed welding to it)

Spot weld, move on 50mm, repeat, repeat.
Next repeat the whole process with an overlapping spot weld on each of the first lot.
Do it again and again until there are overlapping spots all round.
This looks really neat but takes an eternity to do.
Good luck
Dave

weld faster

OK I've found a technique that works for me. Strike up on one side of the join and pull the torch to the other side then let go. Wait a sec, then repeat 2mm to one side. Not striking up on the join means I can dwell enough to start a pool without it blowing a hole and letting go once joined to the other side stops a hole blowing here too. There's still enough heat in the panel that striking up again on the other side doesn't make too raised a weld so there's good penetration across the whole stroke.