So I built an AC Welder from Microwave Oven Transformers.

When I tell people that I built my own welder, I usually get mixed responses. Some people say “Wow, COOL!” and others look at me and probably wonder where the bodies are hidden.

Truthfully, my quest to build my own welder started when I didn’t have the money to buy one and desired to learn to weld so that I can build my own bicycles from plans and from scratch.

The purpose of this is to document my build, not to show you how to build one. the best instructions were at a website that is now offline. I’ve mirrored them here, and they are originally by Randy Gross.

His instructions are top notch. I recommend reading through them so that you’ll know what the heck I’m talking about next:

The first thing I did was get the materials needed. I bought 50 feet of 10 gauge stranded wire and collected 3 microwave ovens. You only need two of them. I disassembled the microwaves and pulled out the transformers as Randy’s instructions say. The next step is to knock the secondary windings out of the transformer.

I tried a number of ways to get them out. I’ll spare you the agony of reading about all the ways that failed. The quickest way was to take an angle grinder with a cut off disk and carefully cut the secondary’s off right at the part where they go into the transformer. Then use a hammer and some kind of blunt punch to knock the rest of the windings out. That was very fast and very effective.

My other suggestion is that instead of winding as many turns as you can get of 10 gauge wire, do 20 turns of 14 gauge wire and then 20 more turns of a second set of wire and then put them in parallel. You’ll end up with 4 leads coming out, with both of them together putting out a higher voltage. Its easier to wind, too!

I followed Randy’s directions and ended up with a nicely working welder that puts out 60 amps. I didn’t get as many winds on my transformers as he did. That is OK though, as the welder works great as it is. I used a pair of old jumper cables as welding cables and one of the ends as a grounding clamp. It really does work well with 1/16″ 6013 rod and does even better with 7014 rod, which is counter-intuitive, but it works great!