DIY Hot Wire Foam Cutter (No Soldering)

You know the expression "like a hot knife through butter"?

Well, it should be changed to "like a hot wire through foam".

You need to try it out to know what I mean.

In this project, I show you how to turn a few household items into an extremely precise foam cutter using very common items and no soldering.

Apart from being incredibly satisfying to use and make, it has many uses such as making ultra-lightweight planes or cleanly cutting the exact shape of foam you need for whatever project you need it for.

• Paper clip
• Battery case (any type can be used, including Christmas lights battery case)
• Heat-shrink tubes or electrical tape
• Push-button switch or any switch
• Toothpicks
• Nichrome wire (I tried with 20 gauge and 30 gauge and they both work)
• 2 AA batteries.

Use pliers or a wire stripper to remove the plastic surrounding the paper clip (if present), then straighten it out and cut it in half.

With the pliers, bend the tip of one half of the paper clip to form a small loop (see image). This will hold the nichrome wire.

Repeat with the other half so you have two of these.

Strip the tip of either one of the battery case wires. Then twist it around one of the half paper clips made in Step 1.

Make sure there is good contact.

Hot glue a toothpick onto one side of the battery case and align the wire with it so that the loop of the paper clip protrudes from the end (see image).

I used a heat shrink tube to encase the wire and the toothpick, but you can also use electrical tape.

For the other wire, cut it about a third of the way from the case. Strip the tip of the wire coming from the case, as well as both sides of the cut-off piece.

For the switch, I used a push-button switch because it's safer. A regular switch can be used and is easier to connect, but there's the risk of forgetting to turn it off.

Connect the tip of the one-third-length wire to one of the 4 legs of the switch by twisting the stripped tip around it and then bending the leg down to tighten it.

There is a line going across the underside of the pushbutton switch. Connect the two-thirds-length wire to the leg across this line from the leg you just bent. If the connections aren't across this line the circuit will always be closed and the switch won't have any effect.

Bend all of the legs and hot glue the switch to the side of the battery case.

Connect the second half-paper clip the same way as in Step 2.

Cut another toothpick so that when it's attached it will be the same height as the first one.

Hot glue it to the side and encase the wire and toothpick the same way as in Step 2.

Cut a length of nichrome wire (for anyone who hasn't heard of it, nichrome wire is a special wire that has resistance and heats up when current flows through it. It's the wire that is used in toasters, hair dryers, some heaters).

Loop one end of the nichrome wire a few times around one of the paper clip's loop.

Now bend the toothpicks slightly toward each other and, while holding them like this, loop the other end of the nichrome wire a few times around the other paper clip's loop, making sure the wire is tight.

The reason you need to bend the toothpicks slightly is that when nichrome wire heats up, it expands and lengthens. So bending the toothpicks like this will force them to naturally straighten the nichrome wire as soon as it heats up.

Now all that's left to do is insert the batteries and have fun!

Tip: This device can easily be modified to whatever size you want. You can add a piece of wood (like a jenga block) to the top of the case and attach something like pencils to the sides of that. Then just run the wires up in the same way and you'll have a much wider and longer foam cutter.