Thanks for everyone suggesting replacing the earth cable on my MIG (I think it was Mr Whippy who done it first!!)...

Just come back from a little welding session after replacing the earth clamp. I couldn't replace the cable because it's attached direct to the transformer secondary So I just attached a shiny new clamp onto the old cable and bingo!!

Much better welds, better penetration etc etc.

It's still a little bit marginal to begin with but once the workpiece heats up it's pretty good. Starting at the edges and moving inwards helps as well.... Perhaps if I got a blowtorch on the pieces and got them good and hot first it would take better.....

So it looks like by notching the material to be welded and moving from the edge to the middle I can weld 1.5mm thick material with a Clarke90 when using 100% CO2!! Wow

The earth clamp is very important you must have a clean connection to the work piece if not it WILL damage the transformer
Jacko

where would i get a new clamp?
mine is very thin metal, and is made jaggy at the end, as a result its like 4 pins touching the metal, and it keeps welding itself to the peice i'm welding...

I got mine from Ebay.....

linky



with some re-usable wire clamps

linky

Get one of those cheap molegrips from the market and weld a M8 bolt to it - best connection you can get

Or just beat a piece of copper pipe round the end of your wire and mole grip or G clamp that to your work.