Strange problem with Nikon F Photomic

Yesterday I experienced a strange problem with my Nikon F Photomic.

The camera had been sitting in my designated camera drawer and had not been in use for a week or two. My Nikkor-o 35mm F2 was mounted on the body and I was attempting to swap it out in the usual way. The lens release button was depressed but the lens mount felt stiffer than usual. I let go of the release button and twisted it back CCW to the lock position and to my HORROR it went past the locking position. The camera was put down as I quietly freaked a bit. Thinking of how to fix it without damaging my beloved kit, I delicately removed the photomic head and tried again. The lens mount was rotated CW and came loose. I inspected all mating surfaces and everything seemed normal. The photomic head was reinstalled and the Nikkor-o was carefully remounted to the body. It now seems just fine and in working condition.

What just happened and should I be concerned about any unseen damage to the lens or body?

There should be a screw on the bayonet, slightly past 6 o'clock when looking at the rear of the lens with the aperture index at 12 o'clock, it's to prevent the lens rotating past the locked position and is radial to the lens' axis. I bet yours fell out. Look for an empty screw hole.

E. von Hoegh said:

There should be a screw on the bayonet, slightly past 6 o'clock when looking at the rear of the lens with the aperture index at 12 o'clock, it's to prevent the lens rotating past the locked position and is radial to the lens' axis. I bet yours fell out. Look for an empty screw hole.

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Ahh, so it's probably the lens. Will the overrotation of the lens damage it?

WILL WORK FOR FILM said:

Ahh, so it's probably the lens. Will the overrotation of the lens damage it?

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Yes, either lens, body, or viewfinder; the aperture coupling will likely suffer.

Ok. so if it is the missing screw and I get a new one back into it, how will I know if there is damage? And will I be in danger of damaging anything else by mounting any of my other lenses?

WILL WORK FOR FILM said:

Ok. so if it is the missing screw and I get a new one back into it, how will I know if there is damage? And will I be in danger of damaging anything else by mounting any of my other lenses?

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I don't know what the problem is, you have not confirmed the presence or absence of the screw. Is the screw floating around inside the camera? Is the aperture stopdown coupling damaged? Is the meter coupling damaged? I can't see the camera and lens, right?

So true!
I'm just worried that I have serious damage. Will have to assess the situation when I get back to home base.

Well I inspected the camera and lens when I got home yesterday and E. von Hoegh called it. DISASTER!!
That tiny little screw was in fact missing from my Nikkor-0 35mm F2. Other than that, the lens "seems" to be ok. Then I focused on the camera. From what I have read recently, it is the aperature coupling lever that could be damaged in the event the lens is over rotated. It "looked" ok compared to my other camera.

This is the part where I made a stupid mistake.

I then decided to experiment a bit. Not wanting to sacrifice my beloved Nikkor-o, I mounted a much less loved series E 100mm F2.5 that I got off the bay for almost nothing to test the waters. The lens mounted in what seemed to be a normal way but when I tested the aperature ring it was obvious that the aperature blades were jammed wide open. The lens was then removed and inspected. After removal the aperature blades were still jammed wide open and a slight nudge to the lever set them loose. Now the aperature blades on the Series E are speckled with oil as seen from the rear of the lens.

My poor old Nikon F is clearly damaged. And I am now left wondering if the Nikkor-O has been damaged as well. As for the series E, I am not sure what to think of the oily aperature blades.

I am now left with some questions.

1) Can the Nikon F be repaired and would the cost be higher than the value of the camera?

2) Should I get the Nikkor-o 35mm F2 inspected before mounting it on another camera? Obviously it need to have a new screw installed as well.

3) Is the Series E 100mm F2.8 inoperative as a result of the oily blades?

1) Don't know what is wrong with it. Anything can be repaired if you're willing to throw enough money at it, also any camera 40+ years old will need servicing if it is to work as it should, so if yours had a recent service having the camera repaired would protect that investment. Another camera will be an unknown quantity.

2) Yes. The aperture coupling to the metered finder should be checked as well.

3) If the aperture is sticky for whatever reason, it may not close fast enough to reach the aperture you have selected especially if it's a small aperture.
If you could post pictures, we would have a better idea. Pretty hard to diagnose without pictures.
At the very least have a good technician look it and the lenses over, only an inspection of the camera will tell and you'll have to do that anyway.

E. von Hoegh said:

1) Don't know what is wrong with it. Anything can be repaired if you're willing to throw enough money at it, also any camera 40+ years old will need servicing if it is to work as it should, so if yours had a recent service having the camera repaired would protect that investment. Another camera will be an unknown quantity.

2) Yes. The aperture coupling to the metered finder should be checked as well.

3) If the aperture is sticky for whatever reason, it may not close fast enough to reach the aperture you have selected especially if it's a small aperture.
If you could post pictures, we would have a better idea. Pretty hard to diagnose without pictures.
At the very least have a good technician look it and the lenses over, only an inspection of the camera will tell and you'll have to do that anyway.

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Ok. Thank you for you input.

I have newer Nikon lens that have a slot in the rear mount ring that the index pin on the body snaps into to lock it in position.
What I would do if I had a lens like yours is to get a digital caliper ($20 or less on Amazon or Ebay, available in hardware or auto parts stores) or a metric ruler with millimeter markings and measure the diameter of the screw hole for the stop screw. Next I would use a small drill bit (#60 to #80) or similar and measure the depth of the hole. The thickness of the mount plate will be close to the length needed.
Search the net for that screw size. Probably a M1.6 x 2 or a M2 x 2. http://www.metricscrews.us/index.php?main_page=index&cPath=98&zenid=7hh8a6ojqtr9onrr05b4ft0u31 has by the piece ordering and screws as small as M.06.
If the factory original has no head and only a slot then a longer screw can have its head cut off. The original may have been a threaded post.

The locking pin in the body should keep the lens from rotating too far even if the little stop screw is missing.
For less than the cost of a caliper you can get a BR-2 lens reversing ring from KEH which should have the screw, and it's likely the same size, or an extension tube should yield the same screw.
As for the body, the over-rotation likely damaged the stop-down lever. Overall F's are pretty robust, it could be repairable but probably not for less than the cost of another functioning F. But if you get a general CLA + the repair, you will presumably have a better camera than some random one that you buy to replace it.

It would be nice to have a good picture of the stop down lever in the body. As far as the lens, it's certainly not the first time oil has kept blades from stopping down.

bdial said:

The locking pin in the body should keep the lens from rotating too far even if the little stop screw is missing.
For less than the cost of a caliper you can get a BR-2 lens reversing ring from KEH which should have the screw, and it's likely the same size, or an extension tube should yield the same screw.
As for the body, the over-rotation likely damaged the stop-down lever. Overall F's are pretty robust, it could be repairable but probably not for less than the cost of another functioning F. But if you get a general CLA + the repair, you will presumably have a better camera than some random one that you buy to replace it.

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Just one of the reasons the OP needs to have a technician look at it, he could have had the released depressed when mounting the lens and in abscence of the screw the lens rotated too far. I usually hold the release down until the lens is almost to the locked position, just to save the tiny bit of wear.
I have in front of me a 35/2 Nikkor O ca. 1970. The stop screw is one of three spaced 120o which retain the rear (black painted) shield, all three presumably go through the mounting flange and thread into the shield. The stop screw is a cheeseheaded type maybe 1.4 +-mm the other two are flush countersunk screws.