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Re: [OM] Helicoid grease (was:50/2 macro vs. 90/2 macro)

Subject: Re: [OM] Helicoid grease (was:50/2 macro vs. 90/2 macro)
From: "Lex Jenkins" <lexjenkins@xxxxxxxxxxx>
Date: Sun, 07 Jan 2001 23:21:05
Cc: olympus@xxxxxxxxxxxxxxx
Hiya,

I suspect a helicoid tensioner is a jig to restore mechanical fit in a worn helicoid. I don't see anything in the focusing mechanism itself that can either be replaced or adjusted.

My guess is the helicoid tensioner either: peens or otherwise modifies the threads very slightly to restore close tolerances; stretches the outer diameter of the male-threaded section; or, reduces the outer diamter of the female-threaded section. Probably the first. Probably not something the average tinkerer could duplicate.

Also, regarding complete disassembly of the lens, it appears to me that keyed wrenches are necessary to remove lockrings retaining optical elements just beneath the filter ring and just above the diaphragm. These lockrings either fit snugly or are secured with threadlocker compound. Can't get 'em loose with just a screwdriver.

I've fabricated keyed wrenches using leftover brass door keys and brass stock from the hardware store. A major hassle but sometimes the only way to do a job right.

I can see some definite complications in the Zuikos that I haven't run across in other lenses:

1. The checkered rubber ring that must be removed to access the screws retaining the focus shroud. In most lenses the checkered focus ring is part of the shroud, eliminating one disassembly/reassembly step;

2. Some optical elements are not permanently mounted in metal or plastic collars, making careful handling far more important - not only to avoid fingerprints that might mar the coating, but I suspect that fungus, mold or mildew can be transferred to the elements through touch. It's probably a good idea to wear latex or thin vinyl gloves while handling the optical elements.

OTOH, Zuikos eliminate a couple of disassembly complications present in Canon FD lenses:

1. It isn't necessary to disassemble practically the entire damn mount when going through the rear;

2. The filter ring shroud (the doodad with the lens info printed on it) can easily be removed using a screwdriver. Some other lenses don't have keyed slots, making it necessary to use grippy rubber tipped tools to loosen those rings.

Regarding fungus, mold and mildew removal, I'm experimenting with a couple of household cleaners like Oxy-Clean, an oxidizing cleanser that doesn't contain common bleach (sodium hypochlorite). I'll report back whether it helps, harms or does nothing.

I'm copying this reply to the OM list for future reference.
===========
Lex Jenkins
===========

From: Dogbreath <hopi@xxxxxxxxxx>
To: lexjenkins@xxxxxxxxxxx
Subject: Re: [OM] Helicoid grease (was:50/2 macro vs. 90/2 macro)
Date: Sun, 7 Jan 2001 09:31:33 -0500

Lex,

Thanks for sharing what you're learning about focus damping.

I'm gonna dig into a dead Zuiko lens to learn about this myself...

John Hermanson refered to something called a helicoid tensioner. That, I
presume, is as important as the grease for the adjustment.


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