I drew this earlier on Solidworks, it basically shows a threaded shafter with a bolt that would go through the top of the head and into the shaft, a lip at the base of the bolt would prevent it pulling through the head, but the plastic would eventually give so it would probably take a brass ring inside the hole in the plastic to stop it losing shape. I am planning to have a go at this next week sometime hopefully.
](http://imageshack.us/photo/my-images/580/75056362.jpg/) Uploaded with ImageShack.us[/IMG]
I drew this earlier on Solidworks, it basically shows a threaded shafter with a bolt that would go through the top of the head and into the shaft, a lip at the base of the bolt would prevent it pulling through the head, but the plastic would eventually give so it would probably take a brass ring inside the hole in the plastic to stop it losing shape. I am planning to have a go at this next week sometime hopefully.