Turning custom screws in small quantities is a significant part of my CNC turning business.
Here is a pair of typical screws I’ve cut.

The screw is turned from 303 stainless steel and is 0.500″ long.
These screws are a bit challenging to turn because they’re so long compared to their small diameter.
Normally they’d be made on a Swiss machine, but the quantities were far too small to justify setting up a Swiss lathe.

These screws are used to mold a thread in a plastic part.
They are experimental; designed to prove out the molding process, so they’re made of free-machining brass.
A total of only 16 of these were made.