What ? It's a transformer that takes 230V/9A in the primary winding and 1,6 Volts on the secondary spot welder. So approximately : 230 x 9 = 2070 Watts -> 2070 / 1,6 = ~ 1200A (i can't measure it 'cause my tool just go to 300A )

Why ? I recovered a microwave oven transformer and didn't know how to use it... It is a tool allowing to assemble metal sheets by welding on very located area. I tested 1.2mm stainless steel welding for now.

How ? I finally picked a huge cable in my garage and i winded it in place of the secondary winding, it started sparkling... I found out a minimum pressure is required to make a good weld, otherwise it doesn't stick. It is still under construction