Because I like to do things the hard way, I made a chuck from scratch instead of buying one from Amazon. This chuck
looks like a really nice one, but I couldn't justify the $170 dollars when I thought I could do it for under $2.
The basic idea of the chuck is to hold the work. I chose to make a 4 jaw chuck because I can hold square things as well as round things. I started by cutting a 5" circle out of some thick MDF to the best of my ability with a jigsaw and then drilled a hole in the middle. I fitted the hole in the middle with a tee nut. Using the same method as the pulley, I threaded this piece onto the shaft and secured it with a nut. Using a very steady file and a moderate speed, I smoothed out the edge of the disc to make it uniform. By holding a pencil up to the disc, you can draw circles on the disc, so I made one near the outside edge.
Next I drilled and tapped carefully lined up holes in aluminum angle. I secured the four pieces of angle evenly spaced around the circle I drew. Through the other hole in each piece of angle, I put a screw. Look at the first photo to see the completed chuck. Basically a piece of wood can be secured in the center of the four jaws by uniformly tightening the four screw, kind of like a Christmas tree stand.
The first picture shows the finished chuck. The second picture shows a side view to show how the shaft needs to end inside the chuck. The third view shows the mounted chuck from an angle.