How to Use a Battery to a Make Simple Hotwire Foam Cutter

Updated July 20, 2017

Foam has been used as a craft material almost as long as it has been around. But foam presents some unique challenges. Cutting, tearing or breaking foam can leave rough edges, make a complete mess and result in nothing but frustration. Therefore, a tool is needed to cut foam accurately, neatly and without frustration. Enter the battery-powered hotwire foam cutter. Making your own hotwire foam cutter eliminates the need for spending money on a pricey prefab one and is a craft all on its own.

Break a paint stirrer in half and drill a hole in each end of both halves. Drill a quarter-inch hole about one-third of the way from the back end of your other two paint stirrers.

Lay one of your half pieces flat and lay both of your full paint stirrers across it perpendicular so that the holes match up. It should form an H. Lay the other half stirrer directly over the other half, sandwiching the full paint stirrers between them. This will be your handle

Bolt your handle pieces together through the holes you drilled using quarter-nch bolts and nuts. Make sure to put a washer between the bolt head and the wood as well as between the nut and the wood. Tighten both nuts hand tight.

Wind 16-gauge wire around one of the longer ends of the full paint stirrers. Pull it tight, and wrap it around the other end. Cut off any excess using wire cutters. Push the opposite ends of the paint stirrers together so that they pull the wire completely tight and tighten the nuts with a combination wrench and a screwdriver. This will keep your wire tight.

Cut a piece of speaker wire about 4 inches long, and separate the two halves. Strip the ends of one piece. Wire two 9-volt batteries together using the piece of wire. Attach the positive terminal of one battery to the negative terminal of the other battery. Insulate the connections with electrical tape, but don't cover the other battery terminals.

Cut a 6-foot piece of speaker wire. Separate the two halves about six inches from the end on one end. Separate the two halves about 12 inches on the other end. Strip all the wire ends.

Tape one of the longer ends of speaker wire along the length of one of your full paint stirrers with the stripped end up by the 16-gauge wire with electrical tape. Leave about an inch or so free at the end. Wrap the stripped wire around the 16-gauge wire. Make sure that the insulation and tape on your speaker wire do not touch the 16-gauge wire. Repeat on the other side using the other long end.

Wrap the short end of your speaker wire to the unused positive battery terminal on your 9-volt batteries. Insulate it with electrical tape. Wrap the other short end around the end of your alligator clip, and insulate it with electrical tape.

Connect the alligator clip to the unused negative battery terminal to use the battery-powered hot knife.


If you need more heat, you can add another 9-volt batteries in series.


Your foam cutter uses heat to cut. Be careful not to burn yourself when using it, and monitor children with it.

Things You'll Need

  • Three paint stirrers
  • Drill
  • ¼-inch drill bit
  • 2 bolts and nuts (¼-inch)
  • 4 washers (¼-inch)
  • Screwdriver
  • ¼ combination wrench
  • 16-gauge wire
  • Speaker wire
  • Wire cutters and strippers
  • 2 batteries (9 volt)
  • Electrical tape
  • Alligator clip
  • Combination wrench
  • Slotted screwdriver
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About the Author

Eric Brown has been writing for over 5 years. He has written for such sites as,,, and many others. Owner of EB Arts Creative Industries, Eric works full time from home. He has been with Demand Studios awhile now and writes primarily on computer related topics for