| Darin McQuoid | Blog | Reviews | Tutorials | River Directory |
Nikkor
105mm f/2.5 AI-S disassembly
On the right, the Nikkor 105mm f/2.5 AI-S Xenotar version, today's project for re-lubrication.
On the right, the Nikkor 105mm f/2.5 AI-S Xenotar version, today's project for re-lubrication.
Unlike the sonnar version of the Nikkor 105mm f/2.5 which came in no less than 13 different cosmetic versions over 12 years, the AI-S model came in one version for 24 years.
It's important to have the right tools as cross type screws on lenses are Japanese Industrial Standard (JIS) not Phillips. A Phillips screwdriver will strip the heads. I suggest working on an old towel as screws bounce off hard surfaces if dropped, and are too easily lost.
First pull the lens hood
forward and
focus to to the minimum focus distance. This reveals three small
slotted screws. Remove and set aside.
Note the size of these compared to lens mount screws, don't drop one.
Note the size of these compared to lens mount screws, don't drop one.
The built in lens hood
unscrews from
the optical block counter-clockwise (when viewing from the front). Then
the whole optical block simply lifts out as one
unit, very slick. Set aside somewhere safe as the elements are exposed.
If you need access to the center element it's done by unscrewing the
block in the middle, counter-clockwise.
Flip the outer casing
over and remove
three JIS lens mount screws & set lens mount aside.
Inside are two metal keys
for the
helicoid. Remove the small JIS screws
for each key and set aside, paying attention to which key came from
which guide. Over years of use they work better where they are worn in
and can affect focusing if switched when installed.
Now we're to the point of
no return. Slowly
unscrew the inner focusing helicoid. Go slow while pulling
the inner helicoid away from the outer body with constant
pressure. It's very
important
to know where the focusing helicoid separates, because it needs to be
threated back on in the same exact spot or focusing will be off when
reassembled.
There are no scribe marks on
this copy,
but I found the helicoid separates where the notch (blue pointer) lines
up M in Made in Japan. Set aside inner helicoid. See the old gummy
lubricant?
Take off the rubber focusing ring. It's important to make a scribe mark for infinity focus.
From left to right, the focusing ring / outer helicoid, distance scale ring and chrome index ring / aperture ring.
Install the inner helicoid. Once the threads start stop, flip the lens over and watch through the rear, lining up the key mount locations with matching slots. Install keys and rear lens mount. Set the optical block back in. If you're having trouble lining things up, just set the aperture to f/22 and adjust the aperture tab on the lens block to fully closed.
All back together except the focusing grip and lens hood.
Install the lens hood, and if you want hard stop infinity focus dead on leave installing the rubber focusing grip for last, as it will take a few trys adjusting and reapplying the scotch tape to get it perfect.
Now celebrate with a beverage of choice! It's much easier than the older Nikkor-P 105mm f/2.5 but easier to mess up the infinity focus and get the helicoids threaded wrong, so pay attention.
Take off the rubber focusing ring. It's important to make a scribe mark for infinity focus.
As a random aside, in the
world of
Nikkor lenses there are many comments about the glory days of AI-S
manual focus lenses and their quality construction, and bemoaning of
that fact that some lenses like the new 18-55mm zooms have parts held
together by scotch tape. Here on the 105mm f/2.5 AI-S the focusing ring
and distance scale are held together by scotch tape, showing a decline
from the original 105mm f/2.5. On the other hand the older lens had one
plastic key for the helicoid while this one has two metal keys.
Now remove scotch tape and
unthread the
outer helicoid. Go slow
while pulling
the outer helicoid away from the outer body with constant
pressure. It's very
important
to know where the focusing helicoid separates, because it needs to be
threated back on in the same exact spot or focusing will be off when
reassembled. Note where it separates from the chrome index ring.
From left to right, the focusing ring / outer helicoid, distance scale ring and chrome index ring / aperture ring.
Clean all helicoid threads and
apply
grease of choice. I
use denatured alcohol, a toothbrush and paper towels to clean the
threads. Thread outer helicoid and
distance
scale back on. Where you line up the scribe mark & distance
scale
dictates infinity focus. I adjusted the infinity focus to allow the
lens to focus past infinity, as I prefer this to a hard stop when using
the Sony A7.
Adjusted slightly from
previous picture,
note how scribe mark is dead on infinity not slightly past it. Tape
with infinity set to desired point and focus to minimum focus distance.
Install the inner helicoid. Once the threads start stop, flip the lens over and watch through the rear, lining up the key mount locations with matching slots. Install keys and rear lens mount. Set the optical block back in. If you're having trouble lining things up, just set the aperture to f/22 and adjust the aperture tab on the lens block to fully closed.
All back together except the focusing grip and lens hood.
Install the lens hood, and if you want hard stop infinity focus dead on leave installing the rubber focusing grip for last, as it will take a few trys adjusting and reapplying the scotch tape to get it perfect.
Now celebrate with a beverage of choice! It's much easier than the older Nikkor-P 105mm f/2.5 but easier to mess up the infinity focus and get the helicoids threaded wrong, so pay attention.
I started with Tomas's
tutorial and explored from there for splitting the helicoid.
For lubrication I've been using CRC White Lithium Grease in a spray can. I spray it in a jar and let the carrying agents evaporate overnight. It seems to be the right viscosity lubricant for AI and earlier lenses, but too thick for AI-S.
For lubrication I've been using CRC White Lithium Grease in a spray can. I spray it in a jar and let the carrying agents evaporate overnight. It seems to be the right viscosity lubricant for AI and earlier lenses, but too thick for AI-S.
HTML
Comment Box is loading
comments...