Introduction: METAL MELTER!

Here's a microwave oven transformer that's been modified into a dangerous little device. Now it can pump out 800 amps of electrical current, so let's use it to melt some metal!


Wildfire-Phoenix (author)2013-09-12

Hello Wildfire Phoenix here. This looks really cool and is something that I will do with microwave transformers (definitely an array of them).

I was wondering could someone, swap the plug for a light switch attached to a powerful car battery for this amazing metal melter?

rbodell (author)Wildfire-Phoenix2015-11-03

No transformers do not work on DC current.

You can however use car batteries and weld with them. I won't explain the process because you can blow up the battery and get blinded by the acid.

I built an arc welder from 6 microwave oven transformers.

Bowtie41 (author)2015-01-19

Would more turns on the secondary give more current?What about more turns in the primary?Can the core be solid steel instead of laminated?Lotsa questions,but I'm looking for more amps,and since I have a mill,thinking of scaling up the MOT to 2x size with a custom core if possible or feasible.

PlasmaGuy101 (author)Bowtie412015-06-30

keep the primary the same, if you want a higher current ( at lower voltage ) output then reduce the secondary winds. NOOOOO! if you use a solid steel core than you'd be wasting half the energy by inducing eddy current which generate heat in the core.

The way I understand transformers, it's all about the ratio of the windings (primary to secondary). So if you maintain the amount of windings on the primary and increase the windings on the secondary, then yes, the current increases. In terms of the core, solid steel becomes permanently magnetized if exposed to a powerful enough magnetic field.

avocadostains (author)2015-06-23

When I made this it was really loud and got really hot quickly. I cut the transformer apart with a grinder. Maybe that was a mistake, is the reason for all those thin ply of insulated metal to reduce eddie current induced excess heating of the transformer? I barely know what Im saying there but Im thinking thats correct because it got real hot real quick.

PlasmaGuy101 (author)2015-06-16

this thing is awesome! i used 14 awg 3 conductor copper wire, and paralleled all 3 conductors. the max short circuit current is 460 amps at 3.69 volts. it easily melts nails.

drkseeker070199 (author)2015-05-22

love your youtube channel, I thought that metal foundry would be great for prototyping parts for projects, good job Grant :3

ehasler (author)2014-11-04

It is a good demonstration piece for showing low voltage with high current

Mich63 (author)2014-05-08

Would this work as a smelter for iron? I have a bunch of rebar lying around, and I'm thinking of trying to melt it down into blocks, then forge them into swords.

dillonxti (author)2014-02-28

have any experience with flybacks

herpingdo (author)2013-09-13

@Wildfire: If you mean using a car battery as a power source, then I would say no. The voltage you would be getting out of the secondary would be way too low to penetrate anything.

mattbeowulf (author)2013-07-28

Well done, sir -- you've earned another fan! The true gem for me though, at the end of the video: high temp solder! *smacks forehead* Thank you for solving the mystery of those PCBs in my parts bin, that my soldering iron won't touch! lol! Do you suppose that components de-soldered with your MMMOT are still any good?

shadow13155 (author)2013-06-24

Could this be adapted to make a metal melting furnace?
A high speed furnace would be so awesome! And handy!

herpingdo (author)2013-05-05

It works quite well, and I've not managed to break it yet, and I am only using 4ish gauge wire.

herpingdo (author)2013-05-04

I browse Instructables quite a bit, but I've never bothered to make an account. I made one though, just to comment here.

I saw this project, and remembered I had a MOT somewhere. I found it the other day, and I decided to modify it. The only tools I had to work with were a 10 year old hacksaw with a dulled blade, and a hammer. 6 hours of intermittent hacksawing and bashing later, and the weld was finally broken! I tapped the primary out with ease, but the secondary was a different story. I sawed and bashed and did everything I could with my tools to it. No luck whatsoever with getting that out. All I managed to do was wedge it in a bit better. I decided to make a trip to the hardware store, and pick up some cable and some tools. I got a chisel, a new blade, and a rubber mallet. That still wasn't enough to bash out the secondary though. I even tried drilling it out a bit, but that was useless. So I decided to bake it at 250 for about an hour, When it came out, I slowly chiseled and hammered and pried away at the secondary, until finally it was all gone. I now wish I had taken a picture of the huge pile of copper strands all over my workbench. From there, it was an extremely easy build. I cable-tied the transformer back together once I was done, and I was ready. At that point it was about midnight, so I figured I would have to wait until the morning. Morning's soon, so I'll let you know if it works or not once I test it! Wow, I've just written a bit of a novel here.

tl;dr: It is extremely difficult to build one of these without the proper tools. Buy the right tools, and bake the MOT in an oven for a bit if the secondary is stuck.

Norway1973 (author)2013-04-26

Could you add a clamp on one cord like the one welding machines and some sort of tip on the other cord so this could work like a plasma cutter? :-)

crazy-blender (author)2013-04-08

Can you wire it in parallel or series of a MOT with its original secondary to get 800 amps@ 2000 volts?

RocketPenguin (author)2013-04-03

Is it just mine, or does you transformer also make a vibrating humming noise? I used two gauge wire as you did, and mine makes a loud humming/vibrating noise. Is that suppose to happen?

Yes. That's the hum of 60Hz AC

Ok. Thanks, just wanted to make sure. Mine doesnt seem to work as fast as yours. The voltage rating is 1.5 volt output, and i dont want to screw up a volt meter measuring amps...

JeanTheDuke (author)2013-03-31


jrstudioboss (author)2013-03-01

Could your transformer, connected to coils, heat high enough for an aluminum melting furnace?

Are you talking about an induction furnace? I think that requires a very high frequency, so this set-up wouldn't work for that.

glennmartinez (author)2012-12-23

I am not easy to impress.....but you have. great videos.....I am going to work at improving my own to measure up.

As an electrician, 30 plus years, I would be interested what the modifications are to the microwave to have the 3 volt out put and high amperage.

Care to share?

Aquaponic Glenn at

I'm not sure if I ever saw your comment before, or answered you? I put up a new video awhile ago on how to make the metal melter. Let me know if you need a link? Basically just replace the secondary with 1-2 turns of 2 AWG copper cable. All the best!

mr fat (author)2013-01-08

This and your spot welder got me in and your You Tube work has made me a huge fun and subscriber! But with your slime and home made solid fuel rockets my five year old daughter is keeping me busy! Keep up the awesome work! Thank you from Alden and my daughter Reghan

Hey Alden! Thanks for your comment and the feedback. It's nice to hear, and tell Reghan I'm glad to have her as a fan :)

SkeptiCol (author)2013-01-04

Must.... make......NOW!

Haha .. yes, do it!

karl_rotsen (author)2012-12-09

hi can you use that thing to make an induction heater/smelter?

Probably? I'm not sure yet, but it's on my list, and when I learn how, I'll make a new video on it. Thanks for asking!

meritsetgo (author)2012-12-09

you just saved me hours of backbreaking work trying to cut rivets from angled iron by sawing them thru with my sawzall, instead, i just melted them!!!

Seriously!? That's creative! Thanks for letting me know :D

poofrabbit (author)2012-11-27

Hey congratulations on being a finalist in the hack it contest! Good luck to you!

Thank you! I didn't know that I was!!

samaddon (author)2012-11-24

Hey, grant are you unknown of the competitions on instructable all you need to enter and i have the confidence that you will be i am waiting to vote for you!

Thanks my friend :)

samaddon (author)2012-11-24

Hi! there,
that's hot but may i know what's the guage and turns of the primary coils of the transformer and what's the approximate cost of that???? cause i need to build it!
Samad Haque.

Thanks Samad.

I'm currently working on a video on how to build this. It cost me about $4 for the wire and lugs because I got some scraps from my brother. The MOT was free out of a microwave.

The video should be done in a couple of weeks. I used 2 AWG insulated stranded copper wire.


st00pit (author)2012-11-14

Awesome video, nice to see one that shows how easy it is to experiment with a MoT.... very dangerous though of course! made myself a 4MoT arc welder and a single that runs a Jacobs ladder in my "laboratory" haha (the garage!)...

Very nice!

I made a 1 MOT stick welder, but you can imagine it was barely enough power to burn a 1/16th rod.

Why did you use 4 MOT's? I've heard 2 is common .. but 4? :) Please tell!!

Thanks for your compliments!

ringai (author)2012-10-24

Have you considered making a small induction furnace to melt metal in a crucible?

I have considered it! I haven't much knowledge yet on how to do it. Have you?

I've been searching for someone who's done it on a DIY scale. I've seen some semi-pro furnaces for precious metals, but they're way outside my budget. If I find anything, I'll share it.

Thanks for the follow up. I appreciate it!

mennis22 (author)2012-11-02

you alway have sweet videos! i know i ave a MOT transformer in my i need to convince my mom of this.

Thank you, and good luck :)

buenhombre26 (author)2012-10-30

Can you give a step by step on how to modify the transformer?

About This Instructable




Bio: Random Weekend Projects
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