not sure i fancy trying this

http://hackaday.com/2009/06/23/how-to-build-your-own-spot-welder/#mo re-11565

Might be worth picking out a coffin first if you're gonna try that!

Nifty idea, but I choose life over a few hundred quid saving

Basic electrical science and completely safe.

it might be safe but i still wouldn't fancy doing a risk assessment for it

Obviously for a 15 quid more you can make it safe as well.

I have worked in a factory (electrician) who make transformers.
We are talking the 11kV upwards ones for mains supplies.
They used a bigger open version of that welder to spot weld 2" X 3/4" copper bus bars.