I’ll describe my weekend story - maybe it will be useful to someone in the future.
Recently, I bought a Nikkor AF 35mm f/2D lens in very good condition, except for an oily and sticky aperture blades. Since cleaning it isn’t a big problem, I decided to do it myself. I have some experience repairing photographic equipment as well as the necessary tools. However, this lens turned out to be quite a challenge. The front name ring was screwed in crooked and jammed. It might have been a factory defect, because once I finally managed to unscrew it, the inside of the lens appeared untouched.
None of the standard tools for unscrewing rings were able to loosen this ring. At first, I 3D-printed a simple ring with a diameter small enough to fit inside the lens. I warmed the part of the front barrel a bit with a hair dryer, then pressed quite hard the lens onto the ring so that the thread would fall back into its proper position.
Now the ring was straight but I still wasn’t able to unscrew it. I really didn’t want to damage the ring or lens, so I came up with an idea for another tool. This time it consisted of two parts: one that I glued to the ring using hot glue, and another that served as an adapter for a cordless drill.
And that did the trick! I think this method can be used to unscrew even very stubborn rings.
I’m attaching photos that more or less show what it looks like.