Ive been looking at these on eBay and wondered if anyone has got or used one?
The idea seems sound and I can pick up a cheap arc welder to power it, the idea of a one sided spot welder for under £100 seems too good to be true tho
The carbon rod ones? Pretty rubbish.
Traditional spot welders apply point pressure as well as fusion whereas the single sided ones just provide heat. You can clamp the two edges together but when you apply the heat from the carbon arc the nearest edge expands and forces itself away from the edge at the back.
Too good to be true is the best way to put it.
They aren't very good and I certainly wouldn't spend money on the gadget and a welder. If you need one I'd spend a little more on a S/H MIG and gas and use that with a hole drilled through one sheet, then filled with weld.
Somewhere there is a thread with some pictures on showing someone having a go with one then breaking them apart to see how they actually worked out. I wouldn't bother.