Sounds like that machine is not up to the job. I have a Lenco spot welder 220 volts, multiple settings. It can do 1/8” easy. Mine has the timer trigger and became one of the best tools I have, got it at a yard sale for $50, first thought it was a big battery charger. Sell what you have and step up to the big boy toy to get the job done right.
Does it look like one in pic?
I have that welder also, $50 at a swap meet, if you grind the tips to size it makes perfect full penetration welds, needs 60 amps 240. They sell a spot welding clamping setup for it, as well as a pin welder for dent pullers.
