Introduction: How to Make the Metal Melter
In this project you'll learn step by step how to modify a microwave oven transformer into a high-current device that can pump out 800 amps of electrical current.
If you liked the Metal Melter you saw in a previous project, here's how you can make your own!
Step 1: Find an Old Microwave
Start by finding an old microwave for free. The bigger, the better.
You can find them in various places, like on free classified adds, or in your neighbors garbage can, like where I found this one.
Step 2: Harvest the Transformer
The transformer is the piece that you'll need, and it looks like this.
CAUTION: Make sure you're familiar with the dangers of opening a microwave, because there are components inside that may still carry a charge and could hurt, or even kill you. Even if the microwave isn't plugged in.
The transformer core is only held together by 2 very thin welds, as seen on the side of this one.
A hacksaw, or angle grinder can be used to cut the weld, then a hammer and chisel used to break it open, giving you access to the primary and secondary coils.
Be very careful taking the primary coil out because you'll need it again. Make sure not to bend, break or scratch it in any way.
NOTE: The secondary coil is harder to get out, and may be damaged by the time you do, but that's ok because we don't need it for this project. However, if you can salvage it intact, it may be a source of thin gauge enameled copper wire for future projects.
Step 3: Re-wind the Coils
Ok, your transformer core should now be bare. These are the "E" and "I" sections of the core, and have been scraped with a chisel to remove glue and paper stuck to the insides.
The next step is to carefully replace the primary coil, an ensure it's snug at the bottom of the core. Then add a 5' length of 2 AWG insulated copper cable. This thicker cable will extend the amount of time a massive electrical current can flow before the cable overheats.
The secondary cable is only wrapped 1-3/4 times around the center.
Step 4: Glue It Back Together
If you don't have a way to weld the base back on, you can use some 2-part epoxy-glue and apply to all the surfaces that will be in contact.
Then clamp it together to let the glue set. I used my bench vise as a clamp and it worked perfectly!
When the glue is dry, your Metal Melter should look similar to this. None of the wires are actually touching each other, but what it can do is very impressive.
Step 5: Melt Some Metal
The output voltage on this is just barely over 2 volts. But the Amps are closer to 800!!
That's enough current to melt iron nails and steel bolts on contact!
Step 6: Spot Welder
I found a practical use for The Metal Melter, in making a Spot Welder like this one. The electrical current can be concentrated to a single point, to fuse thin sheets of metal together. This is known as a "spot weld".
You can see how I made this in a different project.
Step 7: Now You Know!
Know you know how to make The Metal Melter!
If you liked this project, perhaps you'll like some of my others. Check them out at www.thekingofrandom.com

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158 Comments
5 years ago
For all the crazy people who have little or no electrical knowledge. This works off your MAINS SUPPLY NOT SOME SPECIAL POWER SUPPLY , mains supplies differ for different countries, here in the UK it's 240 volts, in the US I think it's 120 volts. You will get different results depending where you are. For the lady who is allowing her kid to mess with this, you need locking up, you adults with no idea will probably kill yourselves, but then that's just survival of the most inteligent.
Question 5 years ago on Step 5
Can you please tell me what power supply i would i use on this unit? i am in australia and run 240V 50hz. i have a few other power supplies 12v 120v 22v 32v. so please tell me which would be the best one and how it conects to the coil? Thanks Dave Ware
Question 5 years ago on Step 6
You go from step 4 to step 5, and poof, you have hot ends... you don't mention a thing on power imput type or voltage, actually nothing on this... though it appears some are figuring out ways...would one more step explanation hurt?
6 years ago
I made one and it hums quite a bit and it throws loud sparks instead of turning red hot and melting. Did i do sonething wrong?
6 years ago
Never mind I got it figured out now ;)
6 years ago
I made this project and am trying to use it to heat up a heating element but when I clamp my electrodes to my element the electrodes get hot but my element does not. But when I barely touch the electrodes to the element, then it gets hot. What am I doing wrong
7 years ago
My 600 volt cord says it has max 30amp take 30 amps isn't this going to be an 800 amp project so it's not big enough can you please help I'm standing right here trying to finish and I have different 600 volt wires to work with don't know which one to put on so I can finish this. Please help
7 years ago on Introduction
7 years ago
Can if the 2 AWG wire at the top?...
8 years ago on Introduction
does it have to be a microwave transformer?
8 years ago on Introduction
Question: Why wouldn't you use a cable with a higher ampacity?
2 AWG is only capable of handling 130amps max (http://www.armstrongssupply.com/wire_chart.htm). Yet even just using 2/0 AWG bumps your ampacity up to 195amps. Would a cable with a higher ampacity heat up slower during use than one with a lower rating? I'm just trying to learn as much as I can before making one of these. I'm also trying to make it usable for longer periods and possibly larger items, or sections of larger items. I'm a hobbyist blacksmith and this would be awesome to use if it could be modified somehow for forging.
8 years ago on Step 5
wait i thought that amps or current were what killed and not the volts because from what I've heard even 2 amps is enough to kill a person..... or was the information wrong? And it doesnt need to be plugged in or anything?
Reply 8 years ago on Introduction
5mA is enough to kill depending on personal resistance and how it goes through your body, this is a high risk project b advised
10 years ago on Step 5
how up the voltage to 12V?
Reply 10 years ago on Step 5
More turns of wire on the secondary coil. Probably about 11-12 turns would do it, but you'll have less amperage as a result.
Reply 8 years ago on Step 5
can u cut the plug for the microwave and attach a nail and use that instead?
8 years ago on Step 5
My son made this and it makes a loud humming noise that is scary! Is it supposed to do that?
8 years ago on Introduction
hey! i just took the primary coil out of my transformer and scratched it a bit ( it was glued in pretty strong) and some of the paper wraping ripped a bit. i was wondering if i just needed to get another transformer or if it would work just the same?
9 years ago on Introduction
I just finished mine!!!!! Moving on to the spot welder!!
9 years ago on Introduction
Oh your Majesty, King of the Random, i have a question: i need a 6V DC transformer that puts out at least 1360mA. I didn't feel like looking all over for it, so i looked around what I had, and found a 300mA 6V DC transformer. Is there any way to modify it and make it put out 1.36A or more ?