Soldering irons are used to melt solder and create bonds between surfaces, mainly on electrical circuit boards. They consist of a handle with a removable heating element. Within the handle are wires that connect to the resistive tip. When turned on, the resistance of the heating element creates heat in the same way as an electric stove. Over time, the heating element can wear out or become covered with cinders, leaving it unable to melt solder. If your element is worn out, you need to replace it. Replacing the heating element is simple and takes only a minute or two.
Unplug your soldering iron and allow it to cool, otherwise you could get burnt changing the tip.
Unscrew the screw or locking nut that holds the tip in place. Cheaper soldering irons may only have a single screw holding the tip in place, but nicer models will have a retaining sleeve that must also be removed with the tip.
Slide the tip and sleeve out of the soldering iron.
Attach the new tip using the disassembly steps in reverse order. Insert the tip back into the sleeve, if you have one, and slide it into the handle. Screw the locking nut or screw back in to complete tip installation.