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How to Turn a Microwave Oven Transformer into a High Amperage Metal Melter!

Dec 13, 2012 04:32 PM
Dec 13, 2012 06:30 PM
Glass blowing process with a heated glass rod.

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, which is enough amperage to melt metal.

Heating a metal nut in a workshop.

If you liked the Metal Melter you saw in my previous project, here's how you can make your own!

Start by finding an old microwave for free. The bigger, the better.

Old kitchen appliances being discarded in a trash bin.
Microwave oven on a countertop.
Old kitchen appliances being discarded in a trash bin.
Microwave oven on a countertop.

You can find them in various places, like on free classified ads, or in your neighbors garbage can, like where I found this one. The transformer (MOT) is the piece that you'll need, and it looks like this.

Electrical transformer with copper coils.

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 two very thin welds, as seen on the side of this one.

Close-up of a mechanical component showing a finger pointing at a weld seam.

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.

Electrical component with copper windings wrapped around a metallic core.

NOTE: The secondary coil is harder to get out, and may be damaged by the time you do, but that's okay, 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.

Metalworking tools in use, focusing on wire being shaped in a vice.

Okay, 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.

Industrial metal components on a workbench.

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.

How to Turn a Microwave Oven Transformer into a High Amperage Metal Melter!
Close-up of a hand holding a black industrial hose connected to a metal fitting.
Electrical transformer with metal housing and insulated cables.
How to Turn a Microwave Oven Transformer into a High Amperage Metal Melter!
Close-up of a hand holding a black industrial hose connected to a metal fitting.
Electrical transformer with metal housing and insulated cables.

The secondary cable is only wrapped 1-3/4 times around the center.

Applying glue to a wooden surface with a stick.
Person performing a woodworking task with a tool and a wooden piece.
Applying glue to a wooden surface with a stick.
Person performing a woodworking task with a tool and a wooden piece.

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.

Close-up of a hand adjusting electrical wiring on a metal component.

Then clamp it together to let the glue set. I used my bench vise as a clamp and it worked perfectly!

Electrical transformer with cables connected.

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.

Digital multimeter displaying a measurement of 2.106 while testing electrical components.

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!

Metalworking tools with a glowing metal piece being shaped.
Wires sparking near a bolt during an electrical connection.
Electrical wires sparking with bright flames.
Metalworking tools with a glowing metal piece being shaped.
Wires sparking near a bolt during an electrical connection.
Electrical wires sparking with bright flames.

I found a practical use for The Metal Melter, in making a Spot Welder like this one.

Heat sealing machine for packaging.

The electrical current can be concentrated to a single point, to fuse thin sheets of metal together. This is known as a "spot weld".

Flame igniting from a precision tool on metal washers.

You can see how I made this in a different project.

Electrical transformer with connected wires and terminals.

Now 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 thekingofrandom.com.

The next big software update for iPhone is coming sometime in April and will include a Food section in Apple News+, an easy-to-miss new Ambient Music app, Priority Notifications thanks to Apple Intelligence, and updates to apps like Mail, Photos, Podcasts, and Safari. See what else is coming to your iPhone with the iOS 18.4 update.

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