Regreasing an overly dampened Nikkor 50mm f/1.4 AI-S

My Nikkor 50mm f/1.4 AI-S was a favourite for many years and was one of my first manual focus lenses and the dampened, but not stiff, focus ring was a nice change from my plastic AF-S lenses. The major benifit at the time with the level of dampening was it helped with precise/limited movement for focusing at wide open apertures.



However with regreasing a number of other Nikkors I've started to prefer a softer focus feel - these are my notes for how to regrease/lubricate a Nikkor 50mm f/1.4 AI-S.

Preparation work

• Remove the bayont and lift off the apeture ring
• FOCOS to INFINITY and mark the upper positions of the helicoid keys

Removing the apeture actuation lever

• unseat the spring and move it to the left
  
  
• remove the large slotted screw that is the pivot of the lever
• remove the 2 screws securing the lever guard and then lift the lever away
  
  
  

Mark your positions

• Extend lens to MFD to expose and loosen the set screw at the front of the lens, and unscrew the retaining ring to exposre the focus adjustment screws
• REFOCUS the lens to INFINITY
• Unscrew the focus adjustment screws and carefully lift off the focus ring with the lens at infinity
• Mark infinity positions on the outside of what are the outer and central (its the narrow ring) helicoids - the central helicoid is where the focus ring attaches. Note the height of the apeture post for future validation of helicoids
  
  
  
  
• Remove the helicoid keys ensuring you keep tabs of which is which
• The central helicoid is not seated all the way into the outer so to ensure correct positioning when re-mating the helicoids, we want to know the relative position. With the helicoid marked in relation to infinity, collapse the helicoid by turning it clockwise as view from rear element - on my copy, it rotates 3/4 of a turn. Scribe a mark across the 2 collapsed helicoids to give futher assurance of correct re-mating
  
  
  

Separating the Helicoids

Inner helicoid / main optical block

Slowly turn rear element housing til you expose the front - this is a single optical block housing the apeture mechansim. Once you have enough purchase of the front of optical block, hold the optical block there and continue to slowly unscrewing and gently pulling away whilst holding the chrome grip stationary with a view of the infinity position. Mark the helicoid separation point relative to the infinity position mark of the NARROW (central) helicoid - do NOT make this relative to the infinity position on the rear/outer helicoid (chrome grip) since the inner helicoid mates with the narrow/central helcioid.

Central helicoid / Outer helicoid

Same technique as above, holiding the chrome grip stationary with a view of the infinity position, unscrew to separate the narrow central helicoid and mark the separation point relative to the infinity position

Clean the helicoids

Use ligher fluid and wipe down with IPA. Normally you can scrub the helicoids quite aggressively with a toothbrush with lighter fluid but because the optical block is also the inner helicoid we should be a little more careful. Drop lighter fluid onto the helicoid and use toothbrush or cotton swabs to remove the original grease - repeat until clean and then use IPA for final clean.

Repeat for the other helicoids.

Apply New Grease

I've been using Japan Hobby Tool #10 grease which is much lighter but gives sufficient dampening for this lens. I applied to the outer helicoid and to the inner helicoid - the central helicoid was "clean" to avoid excessive grease and binding.

Re-assembling

Helicoids

Re-mate the helicoids as you would normally, attaching the outer and central first - reseat these so the fully collapse, verifying the mark you made when they are fully collapsed. If good, back off the helicoids (the 3/4 turn as described above) to align both at the infinity marks.

Work the mated helicoids to spread the grease and to check for feel and remove any excess grease.

Be careful of the lose apeture spring whilst re-mating the inner helicoid all the way and align for the helicoid keys before re-attaching the keys - ensure the outer and central helicoids are still aligned. Again work the mated helicoid to spread/check grease and feel.

Apeture Actuation Lever and the rear

Attaching the apeture actuation lever is relatively simple: start by dropping the lever of the apeture post and reattach the guard and finally the slotted pivot screw - do not tighten: reattach the spring to apeture lever and check movement and then tighten the slotted pivot screw.




At this point you may choose to adjust the apeture ident spring - flatten it more to have a less pronounced/looser click on apeture changes or raise by inserting a small driver underneath and lifting to make the clicks more pronounced/solid.

When attaching the apeture ring, stop down/actuate the lever so the chrome blade of the apeture ring will sit correctly against the post by the guard and allow adjustment of the iris.



Finally reattach the bayonet ring.

Final steps: Focus Ring and Calibration

Re-attach the focus ring, paying attention to infinity position - attach focus ring via its screws but keep the screws lose at this point as you MUST calibrate for infinity focus.



With the lens mounted on a tripod'd camera, focus ring at infinity and adjust the focus ring screw (sliding back and forth) until the camera/lens is focused at infinity - carefully secure one screw taking care not to bump the focus ring. I perform the adjust using a JIS driver on one of the focus ring screw heads so when infinity focus is acheived I simply tighten the screw. Reattach the front retaining ring, reseat the set screw and we're done and the lens should be good for another 40 years!