A hot knife is a tool with a heated blade this is used for cutting though otherwise hard-to-cut materials such as plastic, acrylic and styrofoam. Hot knives can be expensive to purchase, however, and not worth the investment if you only need to use one every so often. You can make a homemade hot knife easily from a soldering iron tip. This method of making a hot knife is cheap and easy and only requires the purchase of a spare soldering iron tip.
Grasp the soldering iron tip by the screw-in side using pliers. By using pliers to hold the soldering iron tip you keep your fingers at a safe distance when hammering the soldering iron tip into a blade.
Put on your protective eye wear to keep your eyes safe from any flying debris.
Hammer the soldering iron tip into a flat blade with a large hammer or mallet. Perform this flattening on a hard work surface that won't be damaged from the blows, such as a stone surface or a spare piece of wood.
Screw the flattened soldering iron tip into the soldering iron and use it as a hot knife to cut through any materials that a store-purchased hot knife could cut through.
Soldering iron tips get very hot when plugged in, and it's very important to remember not to touch the tip or anything the tip has just come into contact with. If you do burn your finger, immediately run it under cold water.