Hi all,
From: AS <alizookoman@xxxxxxxxx>
>I want to take apart a 50mm lens which has stuck blades. Before jumping
into this I wanted to find out if lighter fluid is
>the catch all solution to fixing stuck blades.
It's a common solution, but I've used Methanol for the "several" blades I
cleaned in the past.
>I'll be working with a Canon FD 50 lens.
Is this the later bayonet version or a breechlock mount one? They're
somewhat weird. I have a Canon service video for it (the later one), let me
know if you need additional instructions.
From: "mes9120" <mes9120@xxxxxxx>
>None of the oil will evaporate with the solvent.
Yes, I don't think spraying the blades would be enough. The usual procedure
means taking apart the lens _and_ the diaphragm mechanism, and soaking the
individual blades in solvent. _Sometimes_ soaking the whole diaprhagm
mechanism will work, and you may save some time re-mounting the blades!
>Test any solvent you choose for residue, and do not
>get natural oil from your fingers (sebum) in the solvent.
Absolutely.
>A cotton swab (Q-tip) is handy
>for absorbing the washings but lens tissue is less likely to leave fibers
behind.
It may help, yes.
>Sometimes there is no oil evident on a sluggish diaphragm because
lubrication
>of the pivots has become gummy either by degradation of the lube or
collection
>of dirt in the lube.
Or the linkage may cause problems even with clean blades and pivots.
Particularly, FD lenses have a complex linkage. I presume you already know
their irises are inoperative when unmounted on a camera: bayonet parts
should be moved to the "mounted" position, and then the iris will operate in
a similar way to the OM lenses -- keeps wide-open unless the lever is moved.
>I do not oil the pivots of diaphragms I have cleaned.
Neither did I.
>Do not apply solvents such as MEK, Acetone, or Alcohol to diaphragm blades.
This is interesting, since I always used Methanol. Or is this warning for
Ehtyl Alcohol only? Sorry, I'm very bad at Chemistry.
>Some blades are made of plastic and polar solvents may warp the blades.
>Plastic blades were used on some Agfa/Ansco 120 folders and probably
others.
Then it doesn't seem to be an issue with (classic) SLR blades...
Cheers and good luck,
--
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
--
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