Experience of Disassembling the 28-85mm F3.5 - 4.5 Nikon Zoom Lens

Note: There appears to be two versions of this lens. The tear-down of the other version of this lens can be found here (https://richardhaw.com/2020/02/02/repair-zoom-nikkor-28-85-f-3-5-4-5-ai-s/). I couldn't find a tear-down guide to this lens, hence I am writing it here.

Disclaimer: I am no expert in taking apart lenses, and this is my first time doing so. I hope that the experiences written here can provide a better idea before you decide to tear down your own lenses to fix them. I have never disassembled a lens before, so I didn't exactly have the right tools, or best practices. Do let me know if I made any mistakes, I am still learning. Do not attempt this if you have no prior experience and are not alright with the possibility of damaging the lens permanently

Try to read through the entirety or view most of the images before proceeding.

Background: The Nikon 28-85mm f3.5-4.5 lens was built in the 1990s, but you can still find them affordably 2nd hand. I got mine at a local event for free as it had lots of fungus around the inside of the lens. However, I thought that perhaps I could do a tear down of the lens and clean it on the inside.

• If you can, try to see if disassembling where the dirt is. If you are unable to tell, try to start with the front elements as those are easier to clean and disassemble

I hope this experience can serve as something to read before disassembling the lens, and I hope to collate some of the mistakes that I made.

Recently, while writing this review, I discovered a comprehensive guide to tear-down which you should take a look. If you'd like more general repair advice, read this blog instead as I am no professional at this. https://richardhaw.com/lens-camera-repair-fundame...

Tools
These are the tools I used

• Screwdriver (Small and Medium sized)

  • In hindsight, I should have magnetised the ends of the screwdrivers, which would have helped greatly in preventing the screws from flying everywhere

  • High quality ones will reduce markings on the screw-heads

  • If the size of the screwdriver doesn't fit well, don't force! I learnt this the hard way by stripping some screws. Try to find the right screwdriver or taking it out will be more difficult

• Lens sucker or suction cup
• Lens spanner tool (I did not have this, which I probably should)
• Lens cleaning cloth (the type that can be easily used to clean lenses)
• Rubbing Alcohol (Medical type) or lens cleaning solution
• Bright Torch or Smartphone Torchlight to see inside the lens

Miscellaneous

• Other camera or phone camera to take pictures when disassembling
  • This can help significantly when redoing the steps
• Rubber Glove (Optional)
  • For twisting or having more friction when needed
• Lubricants for the lenses
  • I did not really have these around, but are important for proper lens repair
• Marker
  • To mark positions when disassembling the helicoids of the lenses

  A focus helicoid or helicoid is a tube whose length can be adjusted to vary the distance between the lens and the camera’s sensor to achieve correct focus

For the front lens element - make sure you have a lens sucker and and a lens spanner. I didn't have a lens spanner, and used two Flathead screwdrivers. This is not recommended as I almost damaged the lens while doing so, so try to get these tools if possible.

Start by using the lens spanner and spinning the front lens element in a anti-clockwise direction. (For other lenses, it may be clockwise. I'm not too sure, but do some research for your manufacturer's lens online.)

This should undo the front black ring. Afterwards, use a lens sucker or some suction cup to take out the front lens element.

Gravity may help (I didn't have a suction cup, so this was my only choice) but is a dangerous way of doing so, so make sure you have a soft cushion placed below to prevent any parts from getting damaged.

Repeat this for the other lenses, and make sure to clean each lens thoroughly.

After removing as many lenses as I could, I reached a point whereby I could still see more lenses at the back which had races of fungi, which meant that I had to disassemble the lens from the back.

If you do not see any more dirt in the lenses, you can stop here!

Start by removing the screws marked with the red arrows. This will allow you to remove the black collar - shown below. Strictly speaking, this collar seems to be more of a cosmetic - while it prevents dust from getting into the lens, it is not necessary to allow it to attach to the camera body.

Now, gently pry away the black collar. You will observe that the metal contacts are still attached.

Next, remove the screws holding the metal contacts in place. No worries, it will not fall away as it is supported to a cable. My guess is that this cable is used to send data about the aperture and motor control to the DSLR

Now, we can remove the larger screws holding down. Make sure to separate the screws into different piles. I found it helpful to keep the screws in a linear fashion so I can remember the order which the screws are taken out.

Upon removal of the screws, the metal collar cannot be immediately taken out. This is because it is connected to the bottom in a manner that allows it to control the aperture blades. Thus you may need to zoom in or out of the lens before slowly prying it out.

Once it is removed, you can also remove the bronze coils.

Next, try removing the first lens element with your hands or rubber glove (if you have one) in an anti-clockwise fashion. You can start cleaning the lens element while you are at it. If this is the only lens element which is dirty, congratulations, you need not tear-down further!

Observe how there are 3 screws holding down the rear lens element. We can remove this screws and slowly pry the lens out. This rear element contains both a lens and the mechanism for controlling the aperture.
Just for fun, I adjusted (hopefully carefully!) the control which adjust the aperture blades. Under the light, you can see the whitish mold stuck in the lens. At this point, it would be wise to take out your homemade cleaning solution and give it a nice scrub - careful not to scratch the lens.

I continued looking through the lens, and you can still see there are some blobs of fungus - we need to disassemble more.

Time to remove another metal ring. Careful, place it in the right order!

I couldn't really find any entry points after some time, so I guessed that the screws must be hiding behind the grip of the lens. At this point, I used a screwdriver to pry the grip open. Owing to the age of the lens, the rubber broke almost immediately. **Caution: If you would still like the rubber grip back, make sure to be extra careful at this step as you will likely destroy the rubber!**

Sure enough, there are some screws underneath.

You will see 2 main types of screws - the Flathead type are used for attach the entire front element of the lens in place, while the Phillips head ones are used to control the extent of focus for ring (it provides a stopper to control the lens.

Now: In hindsight, Make sure to do markings - label the parts which extend from the screws as you see in the picture. This is because the next step will remove the lens, and thereafter any adjustments will be tedious and time consuming. I didn't realise this and ended up with a lens that couldn't focus at infinity.

Refer to this page for more info: https://richardhaw.com/2016/01/03/best-practices-...

Go ahead and remove the Flathead screws followed by the Phillips head screws. For me, I couldn't remove one of the Phillips head screws as it was stuck but you should be able to. I still managed to pry the enclosure out though.

However, I tried not to remove any other screws unless they impede the removing of the lens case. If it does not protrude out, it probably dosen't need to be removed. I removed some accidentally and that may have led to me facing focus calibration issues later.

Make sure to make markings before the start and end of the twisting process! This will make it easier to position the lens to screw it in later

Now, this is probably the most difficult and annoying part. Try to remove by twisting the lens and undo the entire zoom lens. This requires a bit of twisting and turning, so be patient. By pure luck, I managed to unscrew the lens out in a anti-clockwise manner, which left me slightly confused. I tightened it back and redid the process, just to observe how I managed to do the previous step.

Once you finally remove the lens element, you can give it a good clean. Congratulations! you have reached the "front element".

Repeat the step of placing the front lens element back in, ensure that it aligns with your marking as earlier. Place back the screws in order too.

Just a note of caution: When you place back the elements, beware of the lens contacts and metal cable. I broke mine accidentally (in the photo) - and this will almost certainly turn your lens into a manual lens aka damage any lens readings (I don't think there's anyway to fix other than finding a replacement cable). The metal contacts and cables are incredibly delicate. Still, I could use it in the camera's manual mode, just without the ability to control the aperture of the lens digitally or read light meter readings.

Also, when placing back, take note to ensure that the metal piece holds the aperture ring correctly. If not, you will lose the ability to adjust the aperture of the lens. I've included a badly drawn image to explain, as I couldn't find a better positioned photo.

Test out the focus and see if you are able to focus to infinity. Also, do ensure that features such as the macro mode of the lens can be activated.