Here is a quick and simple spot welder, suitable for light metals used in building a model turbine. From a microwave oven remove power transformer, relay, and door micro switch. Remove secondary winding from transformer. For the secondary winding ,I used 2 strands of 8 gauge wire long enough for 4 turns, and soldered in a 4 gauge terminal to each end. The 8 gauge was laying around my shop, also having thinner insulation is easier to wind on the core than 4 gauge jumper cable...

I had 2 3/8 copper rods 8 inches long in my junk, along with some 1/4 inch copper machine screws.. The machine screws were turned  to a 3/32 point and threaded into one end of the copper rods, and secured with a  brass lock nut..

The relay needed 18 volts to operate, so I put together some batteries, laid the micro switch on the floor, fastened to a scrap of wood, wired the transformer to the relay..and you are in business.

I clamped one copper rod to the work bench, held the other by hand , and tapped the micro-switch with my foot.. With a little experimenting, you can get very good spot welds...If the points are not precisely over each other, you can blow holes in the metal...

The best thing about this welder, I put it together in about half a day,, and it cost me nothing....

This author assumes no liability what so ever.. You build and operate at your own risk!!!!!!

Welder Pictures

Spot Welder

Spot Welder Points

Foot Switch