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Bliorg
Tinkerer
Username: Bliorg
Post Number: 20
Registered: 11-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 28, 2010 - 10:58 am: | 
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Hi, all -
I knew this lens had a loose focus ring when I bought it, but I want to see if I can't rectify the situation. Ring has about 3/8" play either way in it. Is there a simple way to take up the slack? Any ideas?
Thanks,
Scott |
Waynemel
Tinkerer
Username: Waynemel
Post Number: 147
Registered: 08-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 28, 2010 - 07:52 pm: |
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Have you had the lens apart?
I had a similar situation on another lens (not Nikon). When I removed the front ring, there were simply a couple of screws that had worked loose. |
Bliorg
Tinkerer
Username: Bliorg
Post Number: 21
Registered: 11-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 29, 2010 - 07:48 am: |
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Well, I'm into the lens. It's a bit unlike either example on Rick Oleson's page. The front group came out as a whole, but th aperture assembly is in the barrel. Not seeing anything obvious for tightening the focus ring, though... |
Bliorg
Tinkerer
Username: Bliorg
Post Number: 22
Registered: 11-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 29, 2010 - 09:16 am: |
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Used the Spanner to remove the front group. Now, there's a setscrew (on the right) and some little round pivot-like thingy (on the left):
There's also a setscrew in the focus ring itself.
Removing any of these has no effect on further disassembly. I'm at a loss and don't want to make things worse. I have an SOS out to Rick Oleson; in the meantime, anyone have a clue about this?
Scott |
Glenn
Tinkerer
Username: Glenn
Post Number: 841
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 29, 2010 - 10:31 am: |
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If this lens follows the usual method of construction and your definition of slack at each end of rotation of ring means that initial rotation of ring does not move the optical cells, then I do not think you will find an actual screw/fixing to tighten up the ring. Usually the focus ring is screwed onto the barrel using a fine pitch thread of normal 60 deg form, and the actual optical cell that moves is screwed into the focus ring by a square form helical thread of much coarser pitch. In order to get the optical cell to move in and out over the full length of the helical thread, the cell must be prevented from rotating - if it is allowed to rotate the cell will just move a distance equivalent to one rotation of the 60 deg fine thread on the focus ring. Thus the focusing cell is retained by some form of key running in a keyway and this translates the small angular rotation of the focus ring into a large linear movement of the cell. The slack in the lens is due to the key being worn or loose in some way, although in some lenses this slackness can just be attributed to lack of grease.
Now you should note that the above is only a generalisation as my DIY on Nikon optics is limited to the later autofocus types, but in the above type of construction the focus ring always has one or two limit screws to prevent it being turned off the barrel during use. If this/these screws are removed the focus ring will unscrew off the barrel - always mark position of ring and count the turns as you remove the ring - this usually leaves the key for the inner cell exposed.
I cannot tell from the photo what moves when the focus ring is rotated, but those screws parallel with the optical axis must be a good contender for some kind of stop. |
Bliorg
Tinkerer
Username: Bliorg
Post Number: 23
Registered: 11-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 29, 2010 - 11:26 am: |
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Thanks for the discussion, Glenn. Lemme ask you this: Short of filing a new key of some brass, is there any way to fix this? |
Bliorg
Tinkerer
Username: Bliorg
Post Number: 24
Registered: 11-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 01, 2010 - 02:25 pm: |
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Well, I opened the rear today. The key is apparent, and sits in a couple little prongs, at about 5 o'clock:
No slop there at all. I pulled the rear glass, and couldn't find anything to tighten, or remove for that matter. Rotating the loose ring with the back removed didn't show any signs of looseness anywhere.
The lens is a spectacular performer, and I'd like to get this resolved. Can't anyone help me? |
Glenn
Tinkerer
Username: Glenn
Post Number: 843
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 01, 2010 - 06:13 pm: |
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Sorry that I cannot offer any more advice. As already mentioned I have seen lenses that were completely lacking any grease, on the focus threads, behave like this. The only other thing would be for the alloy finger grip ring to be separate from the actual ring that carries the fine threads, and thus held by two or three pointed grub screws that engage in a 'V' groove - if these screws become loose the ring can slip, not always through 360 degs but by a very small amount sometimes. Only trouble is this method is usually used on lenses of cheaper construction, and the focus ring has a rubber grip band to hide the radially placed grub screws. Obviously you have found no grub screws situated in the grip serrations, otherwise you would have mentioned/tried tightening same. |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 19
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 01, 2010 - 11:40 pm: |
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I think your problem is with the helical guide being out of adjustment. You mentioned that it sits at 5 o'clock in the photo, but the part at 5 o'clock is not the helical guide, it is the control tab for the floating rear element. This is one of the first Nikkor lenses to use a floating rear element. If you look at app. 7 o'clock in your photo, you can see the helical guide beneath the diaphragm control arm. If you put the lens at F/16 you should see the guide and it is held in with three screws. The guide is adjustable-it has a cut in the middle so you can reform it. By slightly spreading it apart, you should be able to adjust the slack. Too much spreading will make focus tight so you will have to work back and forth a bit. I would put some light lube on the sides of the guide where it slides against the focus helicoid. |
Glenn
Tinkerer
Username: Glenn
Post Number: 844
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 02, 2010 - 03:43 am: |
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Thanks Bill for coming in and adding professional repair experience - worth it's weight in gold. Something in the distant memory was niggling about the floating rear element on these fine lenses as the 5 o'clock tab/guide did not look quite right for a helical guide to me. |
Bliorg
Tinkerer
Username: Bliorg
Post Number: 25
Registered: 11-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 02, 2010 - 05:24 am: |
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Thanks for the added info, Bill!
Ok, I opened it up again, set the lens at f/16, and removed the three screws and covering plate from the ring:
I'm not seeing a cut to spread here - guessing that I need to disassemble this thing further to access the split ring? |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 20
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 02, 2010 - 09:13 am: |
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Well, it has been many years since I repaired this particular lens, but I believe that there is a slot for adjusting the helical guide under the silver depth of field ring. Also there is probably a small screw to adjust that spreads the helical guide to adjust it as in other Nikkor lenses. Sorry to not have remembered this earlier but my memory is fading in old age! |
Bliorg
Tinkerer
Username: Bliorg
Post Number: 26
Registered: 11-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 02, 2010 - 09:13 am: |
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Oh, for the record, it's easy to mess up the alignment of the helical with that stop removed. DAMHIKT. Luckily, it's correct again. Phew. |
