My 55mm is the scalloped ring Nikkor-S 55mm f/1.2. According to my calipers, the screw is 2.47mm long, from head to tip.
I've read your 55mm repair guide in the past and found it very informative. I haven't opened up the lens entirely, so I'm not sure if it disassembles identically to the version you worked on, but I believe the only difference is external. I'll find out soon though, as I plan to open it up and relubricate it. When changing focus directions the focus ring knocks slightly, and the finder image jumps. I think there is probably some slack in the helicoid that needs to be filled with lubricant. When I get to that point, I'll be sure to follow your guide.