Repair: Nikkor 105mm f/2.5K

Hello, everybody! I’m busy these days due to some pressure at work. Since I don’t have a lot of time these days, I am going write something short this week. I haven’t written any lens repair articles for some time now so I think that this will be a good warm-up for me. I am going to introduce to you today a lens that has very good value because it’s not very collectible as far as Nikkors go and they are quite boring in terms of style. Just think of it as an “awkward stage” for one of Nikon’s longest-living lens line. Read on.


The Nikkor 105mm f/2.5K is merely a cosmetic upgrade with a new barrel and look to the older Auto-Nikkor-P.C 105mm f/2.5. The optical design is the same but Nikon is known to do small updates to the optical design in production without announcing anything. This is also the case for this lens. I have confirmed with an official source that the lens went a little bit of tweaking during production to fit engineering requirements like fitting a lens element to a reengineered housing. While the elements themselves don’t get tweaked in terms of curvature or spacing as a regular practice, there are times when that happens but the general formula is not changed. It has a new cosmetic design to give the popular 105/2.5 lens line a look that is in-line with the New-Nikkor (K) theme in the ’70s. The all-metal scalloped focusing ring was redesigned to have a rubber grip. The lens barrel is also now mostly black since the shiny silver scheme has been out of style after the ’60s. These are inexpensive even with the factory-made Ai-ring. You can find these for under $100.00 and they offer very good value for the price they’re sold.

IMG_6347.JPGThe Nikkor 105mm f/2.5K still feels substantial despite losing the all-metal construction of the previous version. The rubber grip makes the focusing ring easier to grip and because rubber doesn’t conduct heat as good as metal, it feels better to hold in the winter.

FullSizeRender 13Here are the major cosmetic variations of the 105/2.5 lens family for the Nikon F-mount. I didn’t include my 9-bladed “tickmark” lens in this picture because it’s just a variation of the Auto-Nikkor-P 10.5cm f/2.5 lens that came after it. As you can see, the long-lived lens family underwent a couple of changes throughout it’s production run to reflect the times. Notice that the later Gauss-type lenses are taller than the Sonnar-type lens on the left.

IMG_2324.JPGHere it is together with the Auto-Nikkor-P 10.5cm f/2.5 lens. I converted the aperture ring to be Ai-compliant so I can use it with my newer Nikon cameras. Read my guide on how to convert your aperture ring. Some of these come with factory-Ai rings.

Since this is essentially the same as the slightly-older Auto-Nikkor-P.C 105mm f/2.5, what’s written about the Auto-Nikkor-P.C 105mm f/2.5 is also true for this lens so I am not going to repeat what I wrote about the Auto-Nikkor-P.C 105mm f/2.5 here.

That’s it for the short introduction. We shall now proceed to the disassembly portion!

Before We Begin:

If this is the first attempt at opening a lens then I suggest that you read my previous posts regarding screws & driversgrease and other things. Also read regarding the tools that you will need in order to fix your Nikkors.

I highly suggest that you read these primers before you begin (for beginners):

Reading these primers should lessen the chance of ruining your lens if you are a beginner. Also before opening up any lens, always look for other people who have done so in Youtube and the internet. Information is scarce, vague and scattered (that is why I started this) but you can still find some information if you search carefully.

I highly recommend that you also read my working with helicoids post because this is very important and getting it wrong can ruin your day. If I can force you to read this, I would. It is that important!

For more advanced topics, you can read my fungus removal post as a start. This post has a lot of useful information here and there and it will be beneficial for you to read this.


If you have worked on the Auto-Nikkor-P.C 105mm f/2.5 then working with this lens will be very familiar to you. Just like every lens we are working on, we would like to remove the objective while we work on this lens to keep it safe from accidents.

Fortunately for me (unfortunately for you), the glass looks clean on this lens so I do not need to open up the objective to clean anything. If you need to, then don’t worry because it’s not too different from the average Nikkor lenses of the same era. If you need to clean the iris mechanism then watch the video from Kenneth that I have linked below.

IMG_2301Carefully remove the rubber grip by running a toothpick underneath the circumference of the rubber grip to loosen the glue then lift it up slowly so you can carefully pull it off from the focusing ring. Take care or you will tear the rubber grip. It can be brittle due to its age and there are not replacement parts for this. You can remove the rubber grip later but I opted to do this first for no reason at all. To be honest, you don’t even need to get rid of this in order to dismantle the lens. I just wanted to clean this thoroughly that’s why.

IMG_2302The front barrel can be removed by focusing the lens all the way out until you see the set screw securing the front barrel. Remove that set screw and you can safely unscrew this from the rest of the lens. It can be tight so put a drop of acetone on the screw hole and let that sit for a while to let it work on the glue before you attempt to remove it again.

IMG_2323The name ring can be removed by using a rubber cup. This part is usually glued and it is not necessary for you to remove this but I wanted to clean this lens thoroughly so it had to go. Dirt usually accumulate under this thing so I am not taking any chances.

IMG_2303The front barrel secures the objective so be careful not to drop it! The objective is heavy, I estimate it to be around 100g or so, it can drop straight to the floor if you aren’t careful! It can be easily pulled from the rest of the lens just like this. While pulling it out, make sure that the exposed rear element won’t get scratched by anything inside the lens barrel.

Now that the objective is out of the way and hopefully stored in a safe and clean place. It is now safe to work on the rest of the lens without the danger of damaging the glass.

IMG_2305Remove all of the screws on the bayonet mount to remove it. Be careful not to ruin any of the screws by stripping the heads. Read my guide on how to remove these screws before you attempt to remove them if you are new to this. One important thing that you want to be careful with is the spring for the stop-down lever as you can see from the picture.

IMG_2307The aperture ring comes off just like this. Notice that the spring is now gone. I detached it from the stop-down lever before I remove the bayonet mount to prevent it from damage.

IMG_2308To remove the chrome grip and the decorative sleeve with the scale, remove the 3 screws that secure the chrome grip (green). The tall-headed screw (yellow) is in the way, remove it and store it in a safe place. It is delicate so be careful when removing this. This serves as a pin to couple the aperture ring to the iris mechanism.

IMG_2310The chrome grip and the sleeve can now be safely removed. This part is often glued, old and hardened grease can also cake the inner surface of the sleeve and make it difficult to remove this. If this happened, saturate it with some alcohol or naphtha to soften it up.

IMG_2304This front part of the focusing ring can be removed by unscrewing it. It may be glued so place some acetone on the seam just like what you did on the front barrel. Do not brute-force it, the threads are easily damaged by cross-threading.

IMG_2312The front part of the focusing ring covers the screws that secure the focusing ring to the central helicoid. These screws also serve are your adjustment point when you need to do some adjustments on your lens’s infinity focus. If your lens isn’t focusing properly in the sense that it can’t reach infinity or passes way beyond it then this is where you should be looking at. There will be times when this part gets loose and all you need to do is tighten the screws up and adjust your lens’s infinity focus while you’re at it.

IMG_2313The focusing ring can now be safely removed. These things are glued in-place but it’s not difficult to pull it off since the focusing ring has more surface area for you to grab onto.

IMG_2314It’s now time to separate the helicoids! I prefer to separate my helicoids in this state, you can clearly see everything. Some people like separating the helicoids while the focusing ring is still attached, I don’t like this because the focusing ring covers so many things that can help me put the lens back together again later. As you can see, somebody has worked on this lens before because there is a line at the centerline of the helicoids when the lens is focused all the way to infinity. This will help e later determine if I got the helicoids and the other parts back properly. To separate the helicoids, remove the 2 screws that secure the helicoid key. They can be accessed using the 2 port holes on the main barrel.

IMG_2315Now that the helicoid key is out of the way, you can now separate the outer helicoid from the central helicoid. The helicoid key constrains the helicoids’ movement so that moving the central helicoid via the focusing ring will make it extend or collapse and this is how a lens is focused. I also mark where the helicoids separate by making a small mark. This is very important because this is also the same place where your helicoids should mate. I’m stressing this because many people forget to do this simple step and they end up naming their lens Humpty-Dumpty. Check out my post on how to work with helicoids to help you learn more about working with them. This is essential reading for beginners.

IMG_2316The inner and central helicoids cannot be separated because this part is in the way. This is a stop and it prevents your helicoids from rotating more that its designed range. It can be removed by getting rid of the 2 screws that secure it.

IMG_2317Now that the stop is gone, you can now remove the inner helicoid. Again, don’t forget to mark where the helicoids separate. I always remind everybody to do this and I hope that my reminders don’t fall on deaf ears. I’m getting tired of doing this but I have no choice.

IMG_2318The central helicoid comes in 2 pieces. The helicoid itself and the front part which has a tall extension. This comes in contact with the stop that we removed a few steps before so your helicoids won’t extend until it all comes loose. This can be removed by loosening 3 set screws and unscrewing the ring until it comes off. This part is always glued from the factory and you will have to saturate it with plenty of MEK or alcohol just to soften it up until it’s possible for you to turn it loose. This ring is very vulnerable to cross-threading so be very careful when removing or reinstalling this thing.

IMG_2322Here it is. See how fine those threads are? Again, don’t force it. If it doesn’t move, soak it in alcohol and leave it for a day before you attempt to remove this thing again. There is no real benefit in separating these unless you want to clean the caked grease underneath it. This part tends to accumulate gunk so I always remove it if possible.

If you need to clean your iris mechanism then watch the video above by Kenneth. Please subscribe to his excellent channel. He has plenty of amazing repair videos.

That’s it for the disassembly. There’s nothing unusual with this lens when it comes to the construction. If there’s anything noteworthy then I would have mentioned it in the post. I spent around 3 hours overhauling this thing which is average for this kind of lens. I used plenty of solvents to remove any hardened glue on this lens because this was made in an era when Nikon loved to use glue on almost anything. Sure, it made the lens tough but it’s such a pain for anybody who has to open up the lens for servicing!


This was a boring lens to work with as far as I am concerned because there was nothing out of the ordinary. This lens isn’t suitable for a beginner to work on because of the glue or rather the amount of glue used on this lens. A inexperienced repairman might make the mistake of not using the correct solvent to soften up any glue used on the parts and use brute force to attempt to open something. If you just follow what I said here and use the right tools and solvent then this will probably be OK and there will be less chances for a beginner to ruin this lens. I know that I keep repeating about the glue but that’s the truth when working with New-Nikkors. The screws on the bayonet can also be a pain.

Calibrating the lens for infinity focus is a must with this lens. You can adjust the focusing ring’s range with that big ring on the helicoid shown at the latter steps of the disassembly section. The focusing ring can be adjusted with the 3 screws that secure the focusing ring to the central helicoid. Read my guide on how to adjust a lens’ infinity focusing to make it easier for you by leaving out most of the guesswork.

IMG_6346Here it is with my Nikon F4. It balances really well with the Nikon F4 because the camera is a heavy professional tool. Using this lens on a pro body will mitigate the weight of this lens or at least how it feels to the hand. It’s a very lovely lens to use on the Nikon F4.

IMG_2179Here it is now with it’s siblings. They are one big family! Personally, I like the earliest one the most because I like how Sonnar-type lenses render things. To be honest, you will have to be a maniac to tell which one was taken with what lens just by looking at 2 images but it’s sometimes possible to tell just by observing a photo’s character. I’m not going to claim that I have such skill but I am just telling you that the optical design of a lens influences a lens’ rendering so much that it can leave an impression on you once you saw it at work.

That’s all for today. I hope you enjoyed this short article on one of the best value when it comes to lens purchases these days. If you see one for sale that costs less than $50 or so and if the lens is in great shape, buy it! If you want to push your luck even more, a lens with a factory Ai ring will be a jackpot for that price. You will love this lens a lot and you will find yourself using this a lot for just about any type of photography! Thank you guys for the continuing support! I asked last post if you guys can give me 20,000 hits a month by Christmas as a gift to me and looking at the stats I think I am going to hit 23,000 views this month! This is certainly a very early Christmas gift to me from my readers! Thanks again and see you guys again on the next post. I promise that it will be a long one, Ric.

Help Support this Blog:

Maintaining this blog requires money to operate. If you think that this site has helped you or you want to show your support by helping with the upkeep of this site, you can simple make a small donation to my account ( Money is not my prime motivation for this blog and I believe that I have enough to run this but you can help me make this site (and the companion facebook page) grow.

Helping support this site will ensure that this will be kept going as long as I have the time and energy for this. I would appreciate it if you just leave out your name or details like your country and other information so that the donations will totally be anonymous it is at all possible. This is a labor of love and I intend to keep it that way for as long as I can. Ric.

11 Comments (+add yours?)

  1. John
    Oct 26, 2017 @ 15:59:52

    Great articles -thanks! Have you thought about doing YouTube videos? I’m sure these would be popular. Cheers.


    • richardhaw
      Oct 28, 2017 @ 04:42:55

      Hello, John!
      Sorry for the late reply I was busy. I make videos sometimes but I prefer writing. Check Mikeno62’s channel. He has an awesome video channel!


  2. Kenneth
    Oct 29, 2017 @ 19:08:31

    Thank you Richard, this was a great article, I have the same lens so maybe I should make a film about it, because my lens need some new grease, and I would like to try the Helimax-XP grease just to see how good or bad it will work, compare to the Tri-Flow I normally use in Nikkor lenses.

    Best regards

    (mikeno62 on YouTube)


  3. Bernard
    Nov 02, 2017 @ 02:11:48

    Hi Richard. as always, your articles are very informative. Would the 105 F2.5 Ai have the same disassembly procedure? Thanks!


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