Regreasing dry Micro Nikkor 55m f/3.5 AI Helicoids

The Micro Nikkor 55mm f/3.5 AI is an ~40 year old lens and my copy has various "dry or uneven" areas over its focus range after a few years of sitting idle. Lets see what it takes to fix that.


The problem described is related to the grease on the focusing helicoids - whether the grease has dried up, migrated or just contaminated with dirt over the last decades and the solution is to disassemble the lens and clean and relube/regrease the helicoids. Its not a task for noivices. As expected, Kenneth Olsen has a nice walk through of the steps required to regrease this len's helicoids.



Below are my own notes of the helicoid cleaning and regreasing process

• Locate the grub screw on the collar and release the retaining ring with a rubber cone and then finally the outter collar
  
• remove the bayonet mount and be careful of the long aperture fork - take note of the apeture detent spring orientation, although its not necessary to remove this
  
• pick the optical block out of the barrel, remove and store safely
  
• inside the barrel we have a single long helicoid key that is secured by 3x screws hidden under the distance scale
  

Danger: seperating the helicoids

• remove the rubber focusing ring to gain access to screws securing the distance scale - set the focus at MFD. remove the chrome grab ring to access the helicoid screws
  
  
  
  Mark a reference on all 3x items relative to the focus line to know MFD and potential points of seperation.
  
• remove the helicoid screws and the helicoid key, manually collapse everyything using the central (focusing) helicoid
  
• manually expand the helicoids to the MFD as per reference marks from above - slowly and carefully seperate the helicoids one by one and marking seperation points as reference to the MFD reference marks; start from the chrome/out most/inner helicoid
  
  
  • outer hilicoid: just over 1/2 turn counter clockwise, so the notch will be oppsoite the MFD mark
  • central helicoid: just over 1/4 turn clockwise
  
  Once all seperated, clean the helicoids using lighter fluid and IPA applied by a tooth brush and wiped clean - q-tips with IPA are ran along the threads to remove any small spots. Once cleaned, I will remate the helicoids and dry turn them to verify if there are no gritty bits lefft. Seperate once more to prepare for regreasing
  ^{L-R: helicoids - outer, inner and central}
  

Regreasing with Japan Hobby Tool #10

Whilst this is a relatively short lens, I found that even with the lighter JHT #10 grease, only a VERY VERY thin layer brushed and spread evenly on the helicoids is sufficient to give a good resistance/dampening to the lens. I'd take barely a touch of the grease with brush before applying back and forth over the helicoid.

Having regreased a couple of longer lenses, like a 105mm and a 135mm, I found very quickly that more than a VERY thin layer of grease would result in significantly more torque to focus the lens than was comfortable.

With the grease applied, I would remate the helicoids and turn them individually to determine the resistance. If too much, seperate and use a dry brush to brush over the helicoids, removing excess and then try again.

When the grease is all applied, secure the helicoid key to get a feel of the resistance of focusing again by grabbing the central helicoid - of course this won't be absolute as we are currently not moving the lens objective and its glass elements but this is less of an issue for the small optical footprint of this lens.

Reassembly

Reverse steps from above but leaving OFF the bayonet mount til last. Set the iris wide on the lens objective via the tab, carefully insert the lens objective into the barrel ensuring that the aperture fork engages the tab.

Finally reattach the mount and enjoy.