Nikon 105mm f2.5 L39 disassembly

[Daimon]

Hi,

Looking for some instructions about L39 (LTM - leica thread mount) disassembly instructions for Nikon 105mm f2.5.

I found Repair: Nikkor-P•C 10.5cm f/2.5 which in theory should cover L39 version (AFAIK only focusing unit is different).

Can anyone verify that disassembly is the same? I tried to gently unscrew objective but it doesn't move a bit - I don't want to break anything.

My eventual aim is cleaning and regreasing of the helicoids.

 

[Sonnar Brian]

I can verify that the Optics module of the 10.5cm S-Mount, LTM mount, and Contax mount is the same. I have all three. I've cleaned one of them, and replaced a rear element. I've never had to disassemble and relube the focus mount on any of them.

Daimon has posted fully illustrated how-to instructions in this thread, see page 2!

 

[Phil_F_NM]

The L39 and Nikon RF mount focusing units are completely different between the versions. Mostly due to the nature of focusing cam followers. They turn different directions, talk to the camera differently, and of course mount differently. One thing they do have in common are some of the smallest grub screws you’ll find.
Good luck!
Phil Forrest

 

[Daimon]

Thx! As I understand in LTM version objective also just unscrews itself from focusing unit? Or is there some additional screws to loosen first?

 

[Sonnar Brian]

The Optical block simply unscrews from all three focus mounts. This part is interchangeable between the three. The focus mounts themselves are different.

There are no hidden set screws holding the retaining rings in place, the retaining rings unscrew with a spanner.

The F-Mount Sonnar formula 105/2.5 uses a different fixture for the lens groups. I bought a Nikkor 10.5cm F2.5 without a rear element, learned that I could use the retaining ring from a Jupiter-3 to hold the rear element in place on the Rangefinder version.

 

[lukx]

I have 10.5cm LTM Nikkor just like yours. With mine i couldn’t unscrew the optical block from the mount. Seems like the threads are seized. The front element came off before the lens block, after that there is nothing to hold on to really. If that should happen to you, resist the temptation to grab the aperture ring. You will likely damage it when you apply too much torque.

You can still service the helicoid and clean the glass, but shimming the lens and some other things would not be possible.

Hope your lens does not have this issue!

 

[Daimon]

Unfortunately looks same problem for me. Managed to unscrew but not entire optical block but front part of it

Aperture ring does not go off this direction so cannot really grab anything to unscrew rest of optical block 🙁

Any other hints? How others did unscrew entire optical unit? Did anyone try grabbing aperture ring? Or others were more lucky and entire optical unit just unscrews when grabbing by front silver ring?

 

[lukx]

Unfortunately looks same problem for me. Managed to unscrew but not entire optical block but front part of it

Aperture ring does not go off this direction so cannot really grab anything to unscrew rest of optical block 🙁

Any other hints? How others did unscrew entire optical unit? Did anyone try grabbing aperture ring? Or others were more lucky and entire optical unit just unscrews when grabbing by front silver ring?

View attachment 4823074

Sorry to see that, same exact issue that I had. I went in from the back of the lens, separated the helicoid and stripped it down as much as I could, but I did not manage to separate the lens block fully. I tried to press a rubber wrench to the flat surface at the front, but it was too slippery still to apply the necessary force. But you can in fact service the helicoid. Once the helicoid is separated, you can also reach the back element and unscrew it. That allows you to flood clean the aperture if required.

Don't break the screw heads, use good screwdrivers. Best of luck!

 

[Sonnar Brian]

Screw the section that came out back into the barrel. Turn the F-Stop to F32, as far as it goes. Use a rubber pad (I use a mouse pad) to grip the Aperture ring and the front of the lens as a single point and try turning. If that does not work- sounds like the barrel is cross-threaded, or grease acting like glue.

 

[lukx]

Screw the section that came out back into the barrel. Turn the F-Stop to F32, as far as it goes. Use a rubber pad (I use a mouse pad) to grip the Aperture ring and the front of the lens as a single point and try turning. If that does not work- sounds like the barrel is cross-threaded, or grease acting like glue.

@Sonnar Brian is the aperture mechanism robust enough to endure such a procedure? I was afraid to break off a guiding screw or ruin the grub screws holding the aperture ring in place...

 

[Daimon]

I had to grip front element using rubber and that also required significant effort before it let go. There was no grease, nor apparent glue on threads so maybe it was just 70 years since someone used those threads last time.

By looking at amount of effort required for that I'm also afraid of ruining the aperture unit

 

[Daimon]

Ok thx for the tip. Operation was successful - aperture ring survived. Used silikon pad to grab both silver element and aperture ring as instructed 🙂

 

[Duofold RF]

Could not remember when did I download these images, they are in my file. This one is Nikki’s 85mmf2 ltm, can be used as reference, it is similar to 105mm f2.5. I sued this as reference to CLA my two 105

 

[Sonnar Brian]

@Sonnar Brian is the aperture mechanism robust enough to endure such a procedure? I was afraid to break off a guiding screw or ruin the grub screws holding the aperture ring in place...

I have done this- but you need to really judge the force needed. What you are doing is preventing the front section from coming out by itself. Most of the area being gripped is in front of the aperture ring.

 

[lukx]

I have done this- but you need to really judge the force needed. What you are doing is preventing the front section from coming out by itself. Most of the area being gripped is in front of the aperture ring.

What can I say, I tried it out of curiosity and it did indeed work. It helps to know that the lens will survive. Thanks for another great tip, Brian.

 

[Daimon]

Aperture aperture ring cleaned and regreased 🙂

To separate helicoids I actually need to remove part used for rangefinder coupling? Using those 2 screws on outside of the barrel? Looked inside the focusing unit from the other side and couldn't see any stop screws from the inside

 

[Sonnar Brian]

This is a guess- and is based on working on the Komura lenses and some others.

Try removing the focus ring first- on other lenses I've worked on, that reveals the helical. ALSO- I learned with the Komura lenses to expose the threads, but do not separate them. Too hard to get back together. IF you can find the correct starting position again, sometimes the metal has malformed and will not start. LOTS of filing on a Komura in just the right places to get back together.

 

[Duofold RF]

My memory maybe not correct, here is all I remembered.
You do not need to remove the RF coupler, remove the tripod mount, move the focus to the nearest distance, there should be few screw hold the the black part that hold by your thum, move up to exposure a screw that prevent the focus helical move any further in the closest distance, remove the screw should be able to move the focus helical out, be careful, mark the place where two parts separated, so when you put back it should be in infinite position.

 

[Duofold RF]

I removed the tripod mount, patched the hold to save weight

 

[Duofold RF]

See attached