Nikkormat lens indexing linkage

[abruzzi]

So I just got a Nikkormat FT2 in excellent condition (no dented prism!) I would like to make it my main 35mm because I really like the feel of the Nikkormat, and the 1.5v compatibility makes it simpler than using one of my FTNs. Unfortunately the camera has a problem with lens indexing.

If you know the old Nikkormats you know that you set the lens at 5.6, make sure the coupling pin is pulled all the way down, mate the camera and lens, then twist the lens to lock it on the mount. Then you twist the aperture to the smallest setting, and when you do that action, the camera should make a nice springy “thwack”. At which point you move the aperture to the largest setting, and the camera indexes the lens max aperture, and it can be read as a dot on a little scale from 1.2 to 2.8 to 5.6.

The problem is I’m not always getting that thwack, and when I don’t, the index dot stays at 1.2. Investigating, I removed the lens mount, and I can kind of see what’s supposed to happen (not completely, but the basics.). There is a metal piece with notches spaced at various points, and a lever with a pawl at the end that is clearly intended to engage in the notches, and a long spring that rotates one of the rings (and instigates the thwack.).

I have been able to tease out the thwack by applying a little outward pressure on the ring with the aperture pin. This makes me think something in there is binding. It did seem the notches and pawl had a little lubricant on them. I was thinking of cleaning them, but didn’t know if I should leave them dry, or lube them, and if I lube them, what is an appropriate lube?

 

[BradS]

I can't answer your question but am interested. It is a common problem, it seems. I have several FTN and a few of them behave exactly as you describe. I suspect that old, dried up lube and accumulated dirt needs to be cleaned out and some new lube needs to go in there.

 

[David Lyga]

I have often removed the screws (carefully, as there are washers underneath) on the Nikkormat logo piece, just above the mount area. This reveals the entire 'thwacking' mechanism. Often, I have had to merely lubricate it with lighter fluid as it is vulnerable to getting dried oil up there. The mechanism is not rocket science and you should be able to see it workings and what is wrong by slowly watching it as you run the lever back and forth. - David Lyga

 

[BradS]

I think that there is more to it than what can be seen directly behind the easily removable, "Nikkormat" nameplate. There are springs and a ratcheting mechanism (and other stuff that complicates the matter) directly under the lens mount. I think that the problem is more likely under there.

 

[abruzzi]

Actually I think that David is right. Last time I had the mount off, I noticed that the lever with the pawl had a piece the extended outside the ring. After I put it back together, with every test lens I have (ƒ1.4, ƒ1.8, ƒ2, ƒ2.5, ƒ2.8, and ƒ3.5), if I turned the aperture lever to the smallest aperture, and the thwack didn't happen, I left the aperture in the small position, took a toothpick, and depressed that external bit of the lever, it made the noise I was expecting, then when I turned the aperture to the largest number then back to small, every time the lens indexed at the right point.

I removed the "Nikomat" cover (this was a model from Japan) and saw there is a mechanism to raise or lower a small flat blade that is in the path of that external bit, and is clearly intended to depress it when you turn to the smallest aperture. I'm not quite sure yet why its not working, but it is something in the plates in there that is not fully depressing that release. I'll need to open one of my working Nikkormats to compare, but I do feel like I'm a little closer.

thanks!

 

[David Lyga]

Yes, under that logo is all concerning the 'thwack' mechanism. I have done this many times and it is not as complicated as it first seems. With that logo off, you can follow the pathway for the complete run. - David Lyga