I just adjusted vertical alignment on a Leica M3 rangefinder

I didn't find a post here about adjusting vertical alignment on a Leica M3. Here's a Reddit post I made in the new r/LeicaCameras subreddit yesterday:

Certain Exposures:

I made this post a couple of days ago. I decided to give it a try at home.

For context, the last time I adjusted the focus on a camera, the process took me several days of frustration. I was traumatized. However, that was a stereoscopic camera, and the project was an eventual success.

Anyway, a few observations:

1. First, I confirmed the issue was the body because of comments in this thread. I checked the body against a few loaner lenses. The finder showed the same flaw at the same distance with each lens attached.
2. None of the small US flathead screwdrivers in my generic tool kits fit. I had to use a JIS 2.5mm screwdriver (the green one) to remove the first screw that acts as a "cap" for the second adjustment screw. It can work, BUT, my God, be careful. You need to center the screwdriver and turn it like it's your toddler's wrist to avoid notching the sides of the first screw's groove.
3. The JIS 2.5mm screwdriver (the green one) fits the second screw as well. The second screw is in a body cavity, so you need a screwdriver with a little length.
   1. I did not use any fluids to loosen the second screw. Instead, I gently twisted it about 20 times. I can't emphasize enough how gently I twisted. The screw still looks just like I found it. Unfortunately, I did not discover it in the best condition. I suspect someone else had been there, and they were less patient.
   2. A gentle clockwise turn lowered the ghost image. A gentle anti-clockwise turn raised it. The difference in the screw's position is almost imperceptible.
4. I was unable to turn the second screw comfortably while looking through the viewfinder. Instead, I had to make a microscopic adjustment from the front of the camera and then go back to look. I left the lens on the body.
5. The view is now sharp at infinity. Fortunately, the horizontal alignment did not change. I will test the camera with film again and go through the complete focus range. I already exposed "before" shots to compare to.
6. I would not do this again without screwdrivers that fit the exact measurements. Also, maybe there's some method that professionals use to get the second screw to stick to the new setting? I can imagine it will drift.

Any comments, criticism, or recommendations are welcome.

Thanks, u/coldkennels, u/qqphot, u/petar_d , u/Fit_Celebration_8513.

Click to expand...

There is a four year old Photrio post with a question about adjusting vertical alignment on a Leica M2. I replied to it.

I will share at least one test frame at some point to confirm if things went well.

Some questions for repair folks that lurk here:

1. What brand/model/size screwdriver do you recommend for this?
2. How can we better ensure that the alignment does not drift? Do you "seal" the screw somehow during service?
3. Was there anything harebrained in my write-up?
4. What have you seen go wrong with similar adjustments besides mangling either screw?

Update: you may need to adjust horizontal alignment after. Make sure you check both.

Related thread here.