Home Brew Spot Werlder

Anybody here ever built your own spot welder? I've got some major re-assembly work coming up on my jeep tub & I've been thinking it might be easier/faster to do real spot welds instead of the "drill hole/mig weld plug/grind down" route. I've found a few references on google to plans for units using re-wound microwave oven transformers, intended for use on small projects such as model gas turbines, but there isn't enough detail to convince me they'd work on heavier sheet metal.

So, if you have any experience with something like this or know of any on-line resources that google (Gasp!) doesn't know about I'd appreaciate hearing from you.



Reply to
Howard Eisenhauer
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A long time ago, I built a spot weldor using some 1 kw variac cores and a single turn made of aluminum that pretty much filled the hole in the center of the variac cores. It was plenty powerful enough. I crossed two 3/8 th bolts and applied pressure and current. It welded them into a cross with the bolts almost in the same plane. About four microwave oven transformer cores ought to be roughly equivalent. You will have to wire the primaries in series/parallel and use 240 volts to avoid popping a 120 volt breaker.


Reply to
Dan Caster

Reply to
SimonShabtai Evan

Could you also send me a copy of the schematic. I built a timer several years ago, and would like to see what your approach was.

Reply to
Ken Moffett

I'm sure a lot of people would want to see it - can you post it to the drop-box at

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Reply to

We had one of these at work when I was a kid, it worked great on body panels:

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Since you already have a welder; something like this would probably be quicker, cheaper, easier than building something from scratch. The Eastwood Co sells them brand new for $60:
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Reply to
David Courtney

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