Picture of Making an ARC Welder - Part 1 of 2
How to convert scavenged microwave parts into a useful arc welding machine.  This is part 1 of 2, and focuses on the modification of the transformers.

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Step 1: Watch the Video!

WARNING: Stick welding, and/or the modification of a Microwave Oven Transformer (M.O.T), can be very dangerous and presents risks of UV radiation, shock hazards, burns, fires, fumes and a multitude of other risks.  This project should not be attempted without a thorough understanding of electricity, adult supervision and adequate training.  Misuse, or careless use, of tools or projects may result in serious injury and/or death.  Use of this content is at your own risk.

Step 2: MOT (Microwave Oven Transformer)

Picture of MOT (Microwave Oven Transformer)
In a previous project, I melted the lead wires on my first metal melter.  But the transformer core was still in great condition, so I re-used it to make an AC stick welder!  

The arc welder made sparks fly, but in the end, it wasn't enough power to make the metal stick, and the pieces of work would break apart with very little effort.

If I tried pumping more power into the welder, the wires would overheat and melt. 

So to address this challenge, we'll be using 2 MOTs (Microwave Oven Transformers), because more transformers means more power!

Step 3: Transformers Transform

Picture of Transformers Transform
Preparing the MOTs for a new secondary is exactly the same as the first few steps we took in the Metal Melter project.  As it's a little redundant, I won't spend much time on the step-by-step instructions for that, but if you haven't seen it yet, you can check out the Video, or reference the Instructable.  

gennagonna1 year ago

I have been saving bottle caps

Great Videos ! I'm going to build my own. One last thing : With two MOTs, how to calculate the width, the lenght and the turns to obtain a 30V and 0 120 Amps welder? you say 8 gauge with 18 turns, but if i have a different first coil, would it be the same? Best regards from France
sibi.20092 years ago
Sir how much is the output current from this transformer ?
Grant have you posted part 2 ?
walkerbk2 years ago
Have you posted part two? and this runs on 240 volts??? nice build
iungerich12 years ago
hay grant already made your spot welder and i love it!
when part 2 comes out i will make this but i am getting all of the stuff now
i have 2 wire choices picked out witch one (if any) do your think will be best?



thanks hope you can answer my question
MrPyr0fiRe2 years ago
I am from Germany and I will build this ARC WELDER too.
is this the right cabel

are you going to make a video of the dual MOT stack i saw in your video?
Thanks for asking. I wasn't planning on it. It was just unballasted on 240 volts and I'm guessing it was pulling around 20-30 amps, but not enough to pop the breaker .. even after running for 10+ seconds at a time.
You should make a video. I made I dual stack with a half-resonant circuit (2 microwave capacitors in series) and it gave me arcs about a foot long!!!
wolfgang642 years ago
Grant, great work! I have built your spot welder and have been very impressed.
I have two questions with this one. 1 how small can you take this and can you use this on other metals? You are an impressive tinkerer.
I_StarkGuy2 years ago
You are so awesome!!! And your videos are clear and professional. I will follow you to see your recent videos. I'm planning of repeating some of your projects myself.
The King of Random (author)  I_StarkGuy2 years ago
Thank you very much!
M.C. Langer2 years ago
Amazing Grant! I am eager for the second part!!!! :-)
The King of Random (author)  M.C. Langer2 years ago
Great! I'll have it up in about 2 weeks :D