Thanks Richard, for a fascinating look inside an amazing lens design. My copy has slight wobble from [I think] loose helicoid key(s); maybe I'll see if I can tighten the keys.
One problem I always have: The slot-type grub screws. None of my existing screwdriver tips fit them exactly, and if the tip doesn't exactly fit, the screw will likely be destroyed.
Is there a specific set of slot-type screwdrivers that will fit these old Nikon grub screws without the screwdriver tips having to be re-shaped by filing?