Here he has used a broom handle available from most hardware stores. He has sliced 2 pieces 6mm thick.
After drilling a hole in each he has drilled a hole in either end of these fishing weights. These aren't lead. They make environmentally friendly fishing weights that are quite easy to drill through. They come in different weights so you can make your bobbins to suit your projects.
A screw holds all the bits together.
The last step: Alan discovered that the fishing weight left black marks on his hands in the hot weather. To stop this rubbing off on the threads he wrapped each bobbin with a paper sleeve. These work a treat.
See Kumihimo Braids here.