I got an old weller soldering gun ( iron ) from the dump, but the tip was shot. Easy to buy a new tip, but I thought the replacement tip was too expensive for a gun that cost nothing. But without a tip what use was the gun? So how to make a replacement? A free replacement. Here is how I did it.
Step 2: Procedure
It looks pretty much like the tip is made of copper wire, and I had some wire that was similar to the tip. This wire came from the salvage of romex house wiring, you can do this by clamping one end of the wire in a vise and use a box cutter or knife to slit the outer insulation. Individual strands can be stripped in a similar way. Bend the wire to shape as show in the photo. Slip the old nuts from the old tip over the wires and bend L's into the end. Screw back into the gun and you are done. I made sure the part of the tip that would be used for soldering was well tinned with solder, this helps to protect it from corrosion.
Step 3: Improvements
These gun irons are basically step down transformers they take the wall voltage of 100 or more volts and step it down to the range of a volt. This output now at low voltage, but high current flows through the tip and make it hot.
Old tips fail for a couple of reasons:
Corrosion forms where the nuts connect the tip to the iron this increases the electrical resistance and the tip fails to heat. You can fix this by removing the tip and cleaning both it and the gun where they contact each other, the more bright metal shows the better.
Corrosion on the tip where you solder increases the thermal resistance of the tip and stops your work from getting hot. Clean it off, but you may remove so much material that the tip is shot, then replace the tip.
To stop the corrosion at the soldering point it should always be coated with a layer of solder. Do this as you build the tip and forever after. Some tips are electroplated with a material to resist corrosion. When you wear this plating off the tip deteriorates much faster. I have not figured out a way to protect the tip this way, perhaps a winding of thin iron ( or other wire? )
Step 4: Testing
The iron heats up fast and hot now. Not sure how long the tip will last, but easy to make more. I was worried that this tip might greatly change the characteristics of the iron so I tested with a KillaWatt meter. The power consumption was within a few watts of the label on the gun. This is good.
Step 5: Other Ideas
Others have done this with other kinds of wire, but I think copper is the right stuff.
Here are some links related to this repair.