Manual Nikkor lenses (AI/AIS) become "loose" in the focus ring - why?

[Per Inge Oestmoen]

Hello!

I have quite a few manual Nikkor lenses and they are generally of very high quality, performing admirably well even on modern DSLRs like my D750 which I purchased precisely because I wanted to try and use my old Nikkor lenses on a digital body too. I do not regret my purchase.

However, I may have a problem. I do not know the magnitude of the problem, though. So I consult you for help.

- On several of my Nikkor AI and AiS lenses I have noticed that the tight and smooth feeling is not there. Instead there is a little play in the focusing ring during focusing. It is the "loose focusing ring syndrome" which I have heard about and which absolutely is real.

- What is the cause of this unwanted looseness? Is it caused by wear in the helicoid and focusing mechanism? Or is it the result of something, perhaps some adjustment screws, becoming loose?

- Can/will it progress and worsen over time?

- Can it be remedied, and if so, how? Can I do it myself, or do I have to bring the affected lenses to a repair shop?

Thank you.

[Akira]

Hi, Per, welcome to NG!

The problem is most likely caused by the lost of grease over time.  If you continue to rotate the focus ring whose helical threads has no grease, the helical threads will be worn out.  You need to re-grease them.  Whether you can do it yourself depends on your skill.  Some folks here can do the job admirably.  They should chime in shortly.   

[Bjørn Rørslett]

An alternative and plausible cause is the screws holding the focusing guides in position have started to work loose.

Do get them to a qualified repair shop. If you are located in Oslo, FotoCare is the obvious choice.

[pluton]

Evaporation/sublimation/decomposition of the grease in the helical threads(helicoid) of the focusing mechansm is the #1 cause of the loose or light focus feeling.  Akira is correct in stating that continued heavy use of the dry helicoid may cause damage to the mating threads, which once damaged may or may not be cured by a re-greasing. It is therefore best to regrease at the earliest possible time.  I think that, at this point in time, many of old Nikkor lenses from the 1960's to the 1980's that have the original factory grease in the helicoid mechanism probably need to be regreased.
If you are observing a small area of slack/deadspot/free play in the rotation of the focus ring, there can be other causes, such as a worn or loose helicoid key(guide).  Helicoid keys can sometimes be adjusted to eliminate free play.  A good lens service operator should be able do it.  Be sure to mention it when requesting the service.

[Per Inge Oestmoen]

If you are observing a small area of slack/deadspot/free play in the rotation of the focus ring, there can be other causes, such as a worn or loose helicoid key(guide).  Helicoid keys can sometimes be adjusted to eliminate free play.  A good lens service operator should be able do it.  Be sure to mention it when requesting the service.

This is precisely what I am experiencing. There is noticeable slack and free play, and it is unlikely that the "ailment" is caused by a lack of grease.

[Per Inge Oestmoen]

An alternative and plausible cause is the screws holding the focusing guides in position have started to work loose.

Do get them to a qualified repair shop. If you are located in Oslo, FotoCare is the obvious choice.

The symptoms are in my opinion indicative of something that is loose, more than likely the aforementioned screws. Is it realistically possible for me to perform the necessary tightening of the screws with proper tools (JIS drivers) and a little care, and if so how is it done? If a complete optical disassembly and subsequent collimation of the optical elements is not required, it may be possible to tighten these screws.

[Per Inge Oestmoen]

Hi, Per, welcome to NG!

The problem is most likely caused by the lost of grease over time.  If you continue to rotate the focus ring whose helical threads has no grease, the helical threads will be worn out.  You need to re-grease them.  Whether you can do it yourself depends on your skill.  Some folks here can do the job admirably.  They should chime in shortly.   

Hello Akira!

Thank you.

No offense, but the symptoms seem more consistent with some components in the focusing mechanism starting to get loose. There is a slack and noticeable play in the focusing ring, which can be felt in all directions. Several of my lenses are thus afflicted.

[richardHaw]

your lens needs an overhaul! 

check out richardhaw.com so you will have an idea of how the overhauls are done, this will give you an idea of what is causing it and what and how the repair guy should do to fix it.

do not attempt to do this  yourself unless you have the proper skills or tools or you want to get into this thing seriously as it requires investments in time and money

[longzoom]

In some NIkkors it is possible to restore helicoid. For exs., some of 50/1.4 lenses have inner part of helicoid, which is tight to its place by 3-4 micro screws. The opposite side of such helicoid, which never worked,  has the same 3-4 openings and ready to be switched. Very rarely, but outer part of such helicoid could be turned in opposite direction, too, to be fully restored.  The same to the very small quantity of the old 28, 85, 105/1.8 and 2.5 lenses. If any old lens needs to be re-greased, you will need to open it. So look at it inside - if possible, do it, if not, just re-grease it.  LZ

[Erik Lund]

The guide keys needs to be adjusted, most designs show wear over time.
Clean and lube will make it smoorth again.

In some NIkkors it is possible to restore helicoid. For exs., some of 50/1.4 lenses have inner part of helicoid, which is tight to its place by 3-4 micro screws. The opposite side of such helicoid, which never worked,  has the same 3-4 openings and ready to be switched. Very rarely, but outer part of such helicoid could be turned in opposite direction, too, to be fully restored. ,,,,,

? I have never ever heard of this before; Micro screws - ready to be switched,,, ?

[Akira]

No offense, but the symptoms seem more consistent with some components in the focusing mechanism starting to get loose. There is a slack and noticeable play in the focusing ring, which can be felt in all directions. Several of my lenses are thus afflicted.

Per, no offence taken at all.  Frank and open discussion is one of the beauty of this forum, I believe.

The absence of grease can easily cause the symptom you describe.  As Erik (he is nicknamed "Lens Doctor" here by the way) mentioned, the helicoid guide key can be worn along with the helicoid thread, if you continue to use the lens without the grease.

Richard repairs a lot of MF Nikkors.

[longzoom]

The guide keys needs to be adjusted, most designs show wear over time.
Clean and lube will make it smoorth again.
 ? I have never ever heard of this before; Micro screws - ready to be switched,,, ?

  If helicoid is already wear, clean and lube will work for 2-3 weeks, at most. In some, rare cases, helicoid could be turn in opposite direction, outer part of it could be turned and re-installed inside, and tightened again with already existed micro screws. It is visible, and possible, if non-working part, at the other end of the helicoid, has symmetrical openings, so, skilled person is able to perform such the operation, even if he/she has never heard about. And, please, in your comments, never connect beginning of one's post to the very end, looks confusing, really.  LZ

[Per Inge Oestmoen]

Per, no offence taken at all.  Frank and open discussion is one of the beauty of this forum, I believe.

The absence of grease can easily cause the symptom you describe.  As Erik (he is nicknamed "Lens Doctor" here by the way) mentioned, the helicoid guide key can be worn along with the helicoid thread, if you continue to use the lens without the grease.

Richard repairs a lot of MF Nikkors.

It is clear that the whole tubus is somewhat loose, it is not only the helicoid. When I press the front of the lens where the filter threads are, there is a little play and looseness in the tubus.

Grease is of course necessary in order to avoid excessive wear on the helicoid. Then it has to be an advanced formula that does not dissolve or oxidize over time. There are vast differences in quality and properties of different types of grease and the repair shop knows what do use.

[Per Inge Oestmoen]

your lens needs an overhaul! 

check out richardhaw.com so you will have an idea of how the overhauls are done, this will give you an idea of what is causing it and what and how the repair guy should do to fix it.

do not attempt to do this  yourself unless you have the proper skills or tools or you want to get into this thing seriously as it requires investments in time and money

Yes, several of my lenses obviously need service. I see that unqualified attempts at repair could make matters far worse. For one, I have no chance at all to apply the right grease.

[longzoom]

To the OP - If you are not accepting my advice - nothing wrong with that, really - elementary rules of communication require you to say very simple "thank you", coze I spent time try to help you. LZ