This video will show you how to make a DIY bicycle headset cup remover tool.
To do this at home, you will need a hacksaw, something to secure the tube such as a seat clamp or vise, a file, and pliers.
Start with an old or crappy seat post, however any tube of metal should work provided the diameter is not too big to fit into the bicycle. Thick walled aluminum works great because it is a relatively soft metal and has a low risk of damaging anything. Try to avoid using steel. One size tool will work for both 1” and 1 1/8” steering tubes.
The first this to do is remove the clamp end of the post. A hacksaw will do the trick and it will be easiest if the seat post is secured. Try to make the top as flat and straight as possible.
There is a slight angle at the end of the other seat post end. This will also need to be removed so the remover tool can properly grab onto the headset cups. You can file it down with a file. Now, this end will need to be divided into thirds. Mark where you will do this with a magic marker. It doesn’t need to be exact. Then divide it into sixths. Extend each magic marker line down the side about 2-3 inches. Once you have your guidelines drawn, go ahead and cut around them with the hacksaw. The cuts should be more or less equally spaced.
When you are finished making the cuts, get a set of pliers and pull each prong up. You can bend and re-bend until they are more or less sticking all out at the same angle.
To use the tool insert it skinny end first with the prongs at the bottom. Pull it all the way through until you hear it pop. Once it pops, push it back down so it rests on the headset cup. Then tap the skinny end with a mallet until the headset cup falls out, then turn over and repeat with the other side.