This lens is mechanically very different from its successor, the f/3.5 AI-S but this is a positive given the AI-S version's more complicated setup - the f/3.5 AI follows a common pattern wtih other AI lenses, such as the Nikkor 50mm f/2 AI, and is reasonable simple to service. The tricky problem with the f/3.5 AI is that appears one of rear mount screws is always glued which can lead to stripped screws.
Helicoids
The focus grip is rubber but since your lens could be from 1977 the rubber may appear very hard. Remove the rubber using a toothpick going around the edges. Once the rubber focus grip is removed, you can spin off a focus ring collar which gives access to the set screw on the lens objective retaining collar.
Once the collars are gone, we can pull the single peice objective from barrel body.
On the rear, we can remove the mount and the aperture ring comes on easy. The aperture fork floats freely once the rear mount is lifted and you can pick it out - it has a removal long screw (like the 50mm f/2 AI) but its not necessary to remove that screw - just pick it out.
From the front of the lens unscrew the 3x screws holding the focus ring and remove.
At this point make a 2x reference marks against infinity: one of the rear section (the rear helicoid) below the chrome grip and one on the thin ring (the central helicoid).
When done with your infinity reference marks, remove chrome grip - the grip slides off towards the front. We are now able to access the helicoid key.
infinity marked on the barrel - the mark on central helicoid is obscured
To access the 2x screws to unseat the helicoid key, you must rotate the central helicoid - notice the helicoid key has a "lip" that points to the rear of the lens. Take note of how this looks and relative positions of the central helicoid so can have an easy reference when reassembling.
To get the helicoid key out the way, rotate the front aluminum peice whilst ensuring the central helicoid doesn't move too much to avoid unexpected separation. At this point you could also fully collapse the central helicoid to mark it against the rear block to give you move reference points upon remating.
Seperate Helicoids
Hold the rear helicoid stationary with the infinity mark visible and slow turn the central helicoid whilst applying gentle tugging pressure. As soon as you feel the central helicoid starting to pull away/jitter its almost about to separate. When the central helicoid separtes, mark the position on the central helicoid relative to the infinity mark on the rear helicoid.
separation mark under the lip of the central helicoid
The inner helicoid is seperated through the central helicoid as if it were being removed through the front of the lens. Same procedure as above - hold the central helicoid stationary with the infinity reference mark visible and slowly turning the inner helicoid whilst gently pulling away. Mark the seperation point on the inner helicoid in relation to the infinity reference mark on the central helicoid.
inner/central helicoid separation position
Now seperated, go and clean with the usual tissues, ligher fluid, dish soap, kitchen grease remover (Cilit Bang kitchen grease remove works well once you've done with lighter fluid!) and final clean with more lighter fluid and IPA. When ready use a VERY thin layer of soft grease, like NPC BC-13A on the chrome helicoid surfaces only - for the matting black surfaces I just use the dry brush/whatever is left after applying to the chrome part and wipe over the black helicoid parts.
Remate and you're good.
Optics
The 11 / 8 optics are relatively easy to get to although they are sealed with lacquer and need acentone / IPA to disolve the seals to open up.
group 1 - elements 1-3
The rear element housing is sealed with lacquer from underneath.
rear element 11 on the right
The second group requires a curved lens spanner to unseat - this houses the bulk of the lens elements.
group 2
element 4
element 4 - can be removed from its housing from the rear
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