Nikkor AiS 2.8/55mm Micro Repair

stevemark · Joined: 29 Apr 2011 Posts: 3924 Location: Switzerland

The Micro Nikkor AiS 28/55mm certainly is one of the most iconic macro lenses. Introduced in 1979, it was sold until 2020 - for more than fourty years! The Micro Nikkor 2.8/55mm has - unlike its equally legendary precedessor, the Micro Nikkor 3.5/55mm - a floating focusing mechanism. In addition to the double helix required for close focusing, this additional floating focusing mechanism plus the two mechanisms required for transmission of the aperture setting and the aperture activation result in a rather complicated mechanical construction of the lens barrel.

Early AiS 2.8/55mm lenses usually suffer from a sticky aperture, since the three helices were calling for a grease with low viscsity (which tends to spread into the aperture mechanism, blocking it). In addition it may cause fungus growth. When this problem became obvious, Nikon changed the grease, but the new grease was creating another problem since its higher viscosity would lead to stiff focusing after a few years (or even to a completely blocked focusing ring). In other words: Most of the AiS 2.8/55mm Micro Nikkors these days suffer from either a sticky aperture or a blocked focusing ring. Cleaning and re-lubing those lenses isn't as easy as with ordinary primes, but it's doable if you know how to do it.

Some years ago I got three AiS 2.8/55mm Nikkors either cheap or for free from my local photo store - one with its aperture stuck wide open, the two others with some very stiff or completely blocked focusing mechanisms. Some days ago I decided to re-store them.

stevemark · Joined: 29 Apr 2011 Posts: 3924 Location: Switzerland

PART I - SEPARATING LENS BODY & CRC MECHANISM FROM THE FOCUSING MECHANISM

OK - let's start.

First we remove the bayonet. Be sure to loosen the screws by
1) soaking them with a few drops of acetone for a few minutes and
2) using the correct screwdriver (very important - see here: https://richardhaw.com/2015/12/29/best-practices-part-1/#more-421)

Be sure the lens is set to infinity!!

Now soak these screws with acetone and remove them:

Then carefully extract the lens (including the CRC mechanism, shown on the right) from the main focusing mechanism (shown on the left):

stevemark · Joined: 29 Apr 2011 Posts: 3924 Location: Switzerland

PART II - DISMANTLING THE CRC FOCUSING MECHANISM

Be sure not to mess with the relative position of the two parts of the main lens (they should still be in the infinity position!) and mark the correct position of the two parts of the lens:

Remove the rear part of the lens (including the aperture mechanism) by removing the three corresponding screws (one may be hidden partially/temporally by the aperture mechanism):

Remove these two screws and extract the corresponding guide mechanism (brass!) for the CRC helicoid

Now we can dismantle the CRC helicoid:

stevemark · Joined: 29 Apr 2011 Posts: 3924 Location: Switzerland

PART III - CLEANING THE REAR LENSES

Take the rear part of the lens and use a lens spanner wrench to remove the responding retainer:

After its removal the rear lens as well as the rear inner doublet and a spacer are accessible. Be sure to carefully extract them.

Mark the lens elements as well as the spacer so that you will able to re-mount them correctly (e. g. use a marker). After extracting the lenses you may clean them if necessary (e. g. fungus or haze):

stevemark · Joined: 29 Apr 2011 Posts: 3924 Location: Switzerland

PART III - CLEANING THE APERTURE MECHANISM

Open the aperture mechanism (look at how dirty the blades are ...):

Further dismantle the aperture mechanism. To remove the oil, the aperture blades as well as the other parts of the mechanism now can be soaked in acetone.

If the transmission mechanism is oily (it usually is!) it should be cleaned as well. Dismantle it by removing the tiny collar (us a flat screwdriver which is about 1-2mm wide):

After cleaning everything thoroughly, we now can re-assemble the aperture mechanism:

stevemark · Joined: 29 Apr 2011 Posts: 3924 Location: Switzerland

PART IV - CLEANING AND RE-LUBING THE MAIN FOCUSING DOUBLE HELICOID

Now let's go on cleaning and re-lubing the main helicoid (left part on the image below):

First we have to remove these two screws. ATTENTION - THEY EASILY CAN BE DESTROYED IF YOU DON'T FOLLOW THE PROCEDURE GIVEN BELOW!! Be aware that removing them is the most tricky part of the entire repair ...!

0) These screws are NOT glued with epoxy, even though Richard Haw claims otherwise. It's NOT necessary to heat them up (and potentiually damage the entire mechanism)
1) Pour some acetone in a beaker (about 1 cm is enough), and put the focusing mechanism/aperture ring into the beaker so that the screws are covered with acetone
2) Let it soak for 15-30 min
3) Use the correct (!!) screwdriver
4) Apply a lot of pressure while extracting the screws
5) Do not just turn the screwdrive in one direction, but initially loosen the screws by carefully turning first in one direction, then in the other direction, back and forth (ten or twenty times if necessary)
6) As soon as you notice the screws are loosening, extract them as usual

Once you've removed them, the most difficult/dangerous part is over!

Remove the aperture fork which couples the aperture ring with the iris mechanism:

Remove the aperture ring:

Remove the three screws holding the helicoid key. ATTENTION - THOSE SCREWS ARE DIFFICULT TO REMOVE AS WELL; USE THE SAME PROCEDURES AS ABOVE. They are NOT glued in with epoxy, and heating is unnecessary!! 15-30min soaking in acetone is sufficient:

Now you can separate the two parts of the first helicoid - be sure to mark the point where they separate. It's about at this position (at the 0.7 .. 0.8 m mark):

Now the front ring may be removed:

Separating the two parts of the outer helicoid - DON'T FORGET TO MARK THE POSITION WHERE THEY SEPARATE:

Removing the two screws of the key for the inner helicoid:

Separate the two parts of the inner helicoid AND CAREFULLY MARK THE POSITION WHERE THEY SEPARATE:

The three parts of the main double helicoid (remember there's another [third] helicoid for the CRC mechanism):

Clean the helicoids first with plenty of a good liquid detergent (tooth brush works well), and do the same using aceton. Once the threads are clean, re-lube them with a grease of low viscosity. Do NOT apply much grease; a tiny amount is sufficient - otherwise the focusing will be stiiff in spite of all your work ...

Now re-assemble and enjoy Wink

S

kiddo · Joined: 29 Jun 2018 Posts: 1218

thank you Steve, i´ve had this lens cla´d by shop and they´ve used some grease that makes no fun using the lens , as i´d expect smoothness as yashica/vivitar 55mm at least, before attempting to do it myself, i´d need to buy the proper grease for this nikon threads, so which one would you recommend ?

stevemark · Joined: 29 Apr 2011 Posts: 3924 Location: Switzerland

Doc Sharptail · Joined: 23 Nov 2020 Posts: 1154 Location: Winnipeg Canada

This is quite interesting.
I have a much older variant with the same aperture fork mechanism that I did not dis-assemble- it appears to rotate on some pretty tiny bearings, so I left it alone. Same tensioning spring, though.

Just one un-related question:

Have the coatings changed from the deep green to the pale purple/pink color on these A/i-s variants? Kind of curious as one of your photo's shows some of that green on one of the rear elements.

-D.S.

stevemark · Joined: 29 Apr 2011 Posts: 3924 Location: Switzerland

Doc Sharptail · Joined: 23 Nov 2020 Posts: 1154 Location: Winnipeg Canada