Øivind, I can see a lathe and a milling machine and a whole lot of related tooling & jigs coming into your life sometime in the not distant future....

 

BTW, Good luck with this project,

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 so this project might take some time and patience and the need to borrow or acquire something more powerful than my old Dremel with its ailing batteries, or perhaps use the abrasion tool in a drill press for more control.

Thanks for confirming, Erik, looks like I was on the right track after inspecting the details of the Ring. I already have a 62mm filter stacking cap that can be used with a filter ring as part of that makeshift classical screw-in Nikon cap.

And after more considerations regarding #2-3, it looks like the Dremel approach will be to remove material from inside at the non-female-threaded portion of the Ring, and the male thread of the Ring (closest to the mount) will go away by itself, so hopefully no need to make a vertical cut from the outside to remove those threads, which could be difficult to do cleanly.  It will be quite a bit material to remove so this project might take some time and patience and the need to borrow or acquire something more powerful than my old Dremel with its ailing batteries, or perhaps use the abrasion tool in a drill press for more control.
 

Eternity and beyond.

When fermented honey drink is meant here there is what we call mede!

Nile Rodgers with Spoorpark Live Tilburg (NL)
Z9 AFS 300/2.8VR