Hot-Wire Foam Cutting Nunchucks





Introduction: Hot-Wire Foam Cutting Nunchucks

If you've ever tried cutting foam with knives, it can be a frustrating ordeal. With a material that absorbs a lot of shock, you can't apply sufficient pressure to cut through it. The solution? BURN through it, with your very own hot-wire foam cutter/ nunchucks!

With all the parts parasitized from old, and unused everyday items, you can build this foam cutting contraption for less than five dollars! We did it for $3.50, INCREDIBLE! So let us begin our amazing journey to the world of ninja foam cutting....

This project uses high current and hot wires, so don't burn/ electrocute yourself. Also, beware of toxic fumes, and work in a well ventilated area.

Step 1: Materials Needed...


1. (1) Old hairdryer
2. (1) AC power adaptor, at least 1 amp
3. (2) Pieces of 1/2" PVC, about 8" long
4. Electrical tape
5. Silver bearing solder


1. Soldering iron
2. Means of cutting PVC pipe
3. Ninja
4. Pliers

Step 2: Take Apart the Hairdryer

Disassemble the hair dyer and take out the heating element. On the heating element, there should be coils of thin wire. This is nichrome wire. When current is passed through it, it heats up because it has very high resistance. This property makes it perfect for cutting foam. However, be aware that if the wire you use has too little resistance, you can destroy your adaptor, which is never fun.

Un-wrap the wire coils from the heating element's frame, and snip off a small piece that will straighten out to about 8". Proceed to straighten out the wire with a pair of pliers.

Step 3: Attach Power Adapter

Strip off about a 1/2" piece of insulation from the ends of each of the two wires on the power adaptor.
Then, take the straightened 8" piece of nichrome wire and solder both leads form the adaptor to opposite ends of the wire. Be aware that nichrome doesn't solder very well, and it may take a few tries. Add a switch if desired.

Step 4: Finishing Construction

Tape the wires from the adapter to the pieces of PVC pipe as to make two handles (use different colors of tape for class). Notice the nunchuck resemblance? This will make it so you don't burn yourself, and can cut the foam with ease.

Step 5: Cut Your Heart to Contentment?

When you are ready, plug in the adapter and observe that the wire heats up very quickly. Now that the wire is hot, you can cut through many things, including most types of foam, cardboard, paper, and your own hand (though not advised). Enjoy cutting foam with ease and precision, AND enjoy laughing at your friends while they struggle with their knives and razor blades.



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    Will this cut through Styrofoam?

    only one amp?

    Very nice! A few, very minor, "safety" suggestions (mostly for other users who might build this).

    • Run the wire up through the PVC, rather than along the sides.
    • You could use pipe caps to close off the ends with the wire threaded through.
    • Finger shields: Little disks at the end of the PVC (think sword hilts) to keep your fingers from slipping onto the hot wire. Something like a cap for a lamp.

    No. It is no more safe inside, this is not a dangerous current. It is safer to have it outside so you can see if it is getting hot enough to melt the PVC, and that it cools at a more rapid rate outside. However, the whole idea of using PVC is pretty terrible. Far better would be to use regular copper pipe, this way it's quite heat resistant and it slightly heatsinks the ends of the nichrome wire which is desirable, preserves solder joints too. However, it should not use solder joints at all actually. The proper method of construction with nichrome wire is a mechanical one where it's crimped, screwed, or riveted onto the holder. Finger shields seem pretty pointless. If your hand slips so easily it is advised to wear thick heat resistant (like leather) work gloves.

    I would probably highly recommend against using any form of conductive pipe at all. The idea of something a bit nicer than pvc is probably a bit un-needed at 12vdc. I mean I guess if you maybe coated the pipe so it would no longer be conductive that it might work but just be careful.

    During my quick review I would highly suggest against the copper pipe rout if your using 1 amp dc adaptors or more you only need about .85 amps or so to stop your heart under certain conditions.

    This is incorrect. Far far less than 0.85 amps can be deadly BUT it is not current that kills (per se), it is voltage. Even a few dozen mA is deadly but won't flow without the voltage to push it. You are plenty safe holding some copper pipes, BUT you don't necessarily need to hold onto the bare copper, might as well wrap some tape around them or wearing gloves is even better so your hands have the most reasonable protection possible. The far more reasonable risk to be concerned about is accidentally burning yourself when nichrome wire hot enough to melt foam comes in contact with a material like PVC that melts, and/or gets brittle after exposure to this much heat. At least if it melts you have a more gradual warning but if it gets brittle then the next time tension is placed on it, it could snap apart and the heated wire flies towards whichever arm is holding the end that didn't break. There are several ways the nichrome wire could be well enough insulated, and/or a holder resistant to heat like metal pipe could be used, OR you could do both, use a heat resistant pipe AND both thermal and electrical insulation from that pipe. We need to keep something else in mind though, others have compared licking a battery but not what is happening when you have a nichrome element between two copper pipes. In such a situation the nichrome wire is a load, it is substantially reducing the voltage below 12V. You could probably jump in a pool and be dripping wet, lick one pole while putting the other under your armpit, and never feel a thing with the nichrome wire pulling the voltage down to almost nothing, it would probably read under 3V.

    Then how do you explain 100KV stun guns? Or electric fences? Amperage is the "push" in the equation, not voltage.

    Basic science. Voltage is a difference in potential, that potential is what determines how much current will flow until you reach the limit of the power source. A stun gun is an example of what I wrote, kilovolts of electricity just to make a few milliamps of current flow. Amperage is not the push, it would be like you pushing a brick across the floor and YOU are the determing factor of how far the brick is pushed up to the maximum force you can exert on it. Current is then akin to the weight of the brick, the quantity being moved. Therefore, we don't have to be concerned about the current. If you touch two electrodes with 2 volts and 20 million amps from a power source it will not hurt you. If you touch two electrodes with 2000 voltags and 200 milliamps, you better hope you let go while your body uncontrollably shakes.

    If you are still around and wouldn't mind, may I pose a question about a commonly seen scenario involving cardioversion or defibrillation using electric current?