Q re: Nikon lens disassembly

This question has to do with disassembling a Nikon 50mm f/2 lens, sn
311xxxx (late-series non-AI). The problem is a fungus infestation (not
too bad) on the inside surfaces of the glass elements; the lens
otherwise is in perfect cosmetic and mechanical condition. If fixed,
this will be a good lens; if not fixed, it's a throwaway. I figure I
have nothing to lose by trying drastic measures.
I was able to remove the front and rear lens cells from the barrel.
The difficulty is in opening these cells to get at the fungus.
The retaining rings are sealed with a lacquer-like sealant. No
reasonable amount of force with a spanner wrench will move them. (I
determined that it was lacquer because a small amount left on the
surface of a retaining ring dissolved easily in lacquer thinner.)
Neither heat (carefully applied to the outside of the rings with a
soldering iron) nor penetrating oil made any difference.
I'm proposing to leave the lens cells immersed in lacquer thinner for
a few days to try to remove this sealant. My worry is that this might
un-cement any compound lens elements.
Has anyone here disassembled one of these lenses, and can offer any
suggestions?

Alexander Arnakis

Re: Nikon lens disassembly

Hopefully, cemented element groups don't need to be separated, even to
clean fungus out of the lens. To all intents and purposes, these
cemented elements are a unit. The one exception is where separation
has already started (visible as concentric bubble-like lines when
looking through the lens). If such a lens is to be saved, the elements
must be completely separated (using heat in an oven), all traces of
the cement removed, and then the elements must be re-aligned and
re-cemented. (Edmund Scientific sells special lens cement for this
purpose.) This is where a collimator would be needed. Personally, I
think lens element separation is worse than fungus in resulting in a
death sentence for that lens. Time to toss the lens.
Now, adhesives (like lacquer sealant) to attach the glass elements
within the mounting rings are another matter. Those should be
dissolvable without causing more damage.


Alexander Arnakis

Re: Nikon lens disassembly

I would not consider a lens with 6 or 7 elements "simple". But, you use a
collimator to determine that you have carefully maintained the
order/orientation of the elements and have properly tightened the rings
down.
You could, of course, just try taking some pictures with it after you have
gotten it back together.
One thing extra: what do people use to cement the elements back together?
Jim


Jim

Re: Nikon lens disassembly

On Mon, 29 May 2006 12:11:42 -0400, "george" <nowhere@newsonly.com>
wrote:
Thanks. I've heard that the Tomasy books aren't very specific, not
really like repair manuals. The consensus seems to be that they're a
waste of money, if you want to get into the nitty-gritty of trying to
repair an actual camera. I've got all the available reprint materials
from National Camera, and those aren't very helpful either.
It seems that the only way to really learn to repair the old
cameras/lenses is by experience, and trial and error. That's why I
asked, to possibly profit from someone else's mistakes, before I make
my own.
Why would a collimator be necessary for something as simple as a 50mm
prime lens? The lens elements are all fixed within rings, and there
are no adjustments possible. When reassembling, all you need to do is
be careful to maintain the order/orientation of the glass elements,
and tighten the rings down.


Alexander Arnakis

Re: Nikon lens disassembly

...
There is a book on Nikon repair (available at places like Amazon --
actually, there are three of them by the same author, so make sure you get
the right one) that does deal with some lens repairs AND tells you how to
cheaply make your own collimator (sp?) which is a must once you start taking
out lens elements.
Good luck.


George

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