This is a collet/expanding arbor made out of PEEK (A high temperature plastic that is very chemical resistant)
The part started as a longer bar of PEEK. The relief holes in the slots where drilled before turning the outside/inside contour.
Turning the outside contour – PEEK turns very nice but due to its brittle nature care has to be taken not to chip corners or edges.
Tool life is good, drilling can produce a lot of friction and heat. Cooling and slow surface speed help.
The internal taper was turned with a form tool:
Cutting the slots on the first side using a circular saw blade on the milling machine:
Then the part was cut off with some additional stock.
Machining the second side was a bit of a problem, due to the slots it was way to flexible to be held in a chuck with soft jaws. The radial pressure would have collapsed the part.
I decided to turn a „clamping pot“ out of PVC that the part fits in very snug and is secured with a pressure pad and the tailstock.
This allowed to finish the second side of the part on the lathe:
The same clamping pot was used on the milling machine. Not beeing able to use a tailstock for slitting the second side of the part, I added a number of M3 screws that clamp the part in axial direction.