Fixing a Nikkor 105mm f/2.5

[Thomas G]

Some time ago I was able to acquire a 105mm 1:2.5 for a bargain.
The optics were fine, mechanically it wasn't so much and obviously it had been fuzzed around with non appropriate tools.
I started working on the lens some time in fall 2015.
There were a few obstacles to work through, abused screws, sticky dirt, and some super sticky glue in unusual places,
obviously work arounds of some kind.

Considering Roland's serials listing the lens belongs to the following group:

Type	Lens	Country	Scr	Notes	Start No	Confirmed	End No	Qty	Date
Ai	105/2.5	MIJ	5+			764011-897333		157333	(1977)-Sep 1981

That was before I joined NikonGear and there are no documentation photos of the dismanteling process.

[Thomas G]

Post documentation.
All parts came apart with some effort.

The first show stopper was the front ring, which was stuck with the tube mount ring.
I was able to drill out the screw which usually keeps the main thread in position.
Unfortunately it did not improve the situation at the time:

[Thomas G]

I figured that applying force may damage things and nibbled the 3 front screws out.
(I hope that they are not part of any adjustments system as I was not able to mark anything in the small space available)

One of the 3 holes shown:

[Thomas G]

The whole disassembled lens cacrefully stored away:

[Thomas G]

Front ring and tube mount ring were smoothere in 'the juice' for like 3 month.
A few days or weeks usually would do it but I had no time working on it anyway.
The juice is a proven combination of weapon oil, some synthetic engine oil and a solvent.
I finds its way into mechanically stuck threads, into tight fittings and such.
I deals with dirt and acids as well. Crawls under no so well sticking glue, even under well sticking but not well used glue.
Can be support with warming up the parts.
The issue was: I did not now is the threads were glued together.
Even worse: if the possible glue was of the epoxy type light heat will only make it stronger (up to about 180°...).
So I let it sit in the juice for a long time.
Juice shown in it's top coverable tin. The jelly is a result of some reaction, cool temperature and the dissolved solvent.

[Thomas G]

A few days ago the ring assembly was taken from the juice and swiped clean on the outside.
Still stuck. The usual rubber tools did not do it.

Instead of heat the decision was to use cold.
The idea was to quickly deep cool the inner ring while keeping the outer ring warm.
A basic device was build to prevent the vapor cooling spray to boil away on the outer ring and concetrate the thermal effect on the inner ring.

Device and deep freeze spray:
(related: http://nikongear.net/revival/index.php/topic,2411.msg43070.html#msg43070

[Thomas G]

The procecure was as follows:
- use high friction protection gloves of the sticky type to prevent skin irritation or damage as caused by cold
- spray one full turn of the freezing solvend on to the inner ring
- immediatly try to twist of the rings from each other (with some force, if need be)

It worked on the first attempt:

[Thomas G]

Now it's time for re-lubing (again, too sticky) and re-assembly

[richardHaw]

Hello is this the same version as this lens?
I just overhauled one a month ago. Gonna write a teardown one of these days in richardhaw.com where i publish my teardowns.
There is a teardown on the net made by somebody else.

[richardHaw]

Wong photo sorry 

[Thomas G]

Neither one. Quite similar to the second but only F/22.

[Erik Lund]

Thanks for the freezing tip! Recently Bjørn and I used heat to free a stuck glass element from a lens housing.

[richardHaw]

Neither one. Quite similar to the second but only F/22.

oh, that's basically the same lens mechanically with very little differences (and optically) there wasn't a lot changed from K to Ai. Servicing this lens was a joy for me.

[richardHaw]

Thanks for the freezing tip! Recently Bjørn and I used heat to free a stuck glass element from a lens housing.

it might be pitch.  heat is very good for that. i learned to heat pitch from my mechanic before when he was fixing my car's undercarriage. i was told that older japanese cars use them for waterproofing

[richardHaw]

i need to get that freezing spray