This is a tool that I've been missing for far too long. With all the styrofoam I have been hoarding for years it was time to make a hot knife, so I could start carving up patterns, prototypes and molds for lost foam casting. As it turned out I had everything I needed on hand.
- Some random brackets, nuts & bolts
- An old electric heater
- An old 12V 850mA transformer
 The NiCad wire from the heater element makes a perfect hot knife and the ceramic insulators are ideal for insulating from both the heat and the electrical current. The wire can also be shaped and reshaped many times without breaking. |  |
I started with a 12Vdc 850mA transformer wired to each terminal, but burnt up three before I found a 9Vdc 750 mA transformer that worked more consistently. Even with the 9 volt power adapter the transformer gets too hot to hold after about 45 seconds of use. I decided to use my adjustable power supply, which proved to be the superior choice for extended use of the hot knife.
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