At 4:21 AM +0000 1/11/04, olympus-digest wrote:
>Date: Sat, 10 Jan 2004 14:35:38 -0800
>From: Moose <olymoose@xxxxxxxxxxxxx>
>Subject: Re: [OM] Help - stuck filter
>
>The small versions of friction band wrenches can also be a help.
>
>One thing to be aware of is that the 'stuck' is often a matter of
>galling between aluminum threads. This is not a matter of tightness per
>se, but of a metal specific reaction (chemical? mechanical? both?)
>between surfaces in contact.
Basically the metal is welding at the points of contact and then the little
welds tear out, then weld, then tear out, ... Aluminium is particularly prone
to galling. Brass is almost immune, even if dry. The aluminium is generally
hard anodized to prevent galling "in normal use", and this mostly works. If it
didn't work, it would not be possible to use aluminium threads, I think.
>Things to try are varying the angle and
>amount of twisting pressure, applying varying amounts and frequency of
>pressure at right angles to the threads to work things loose and even
>letting it rest between trys. I've had the same problem, worked at it
>for some time, put it down in disgust, then later had it unscrew with
>very light pressure. I think more pressure can actually make it worse.
Yes. The key is to find a way to apply enough torque without causing the ring
to distort, because the distortion causes more galling, etc. Camera gadget
catalogs like Porters Camera have little plastic ring wrench sets that work
very well. They look like scaled down bottle openers, being an almost full
ring with two little handles. The rings are made in a series of sizes to fit
the usual filters, and when used the two little handles are pinched together
causing the ring to tighten upon the hapless filter. The wrench in fact forces
the filter to become round even if it had been distorted, thus increasing the
liklihood of success.
I suppose one could make such a wrench from a sheet of 3mm plastic (or even
metal), but the store-bought sets are so cheap and effective that it doesn't
seem worth the effort.
At 4:21 AM +0000 1/11/04, olympus-digest wrote:
>Date: Sat, 10 Jan 2004 17:53:03 -0800
>From: "Nick Taylor" <ntaylor@xxxxxxx>
>Subject: Re: [OM] Help - stuck filter
>
>Thanks to all that offered advice on unsticking my filters. Having been male
>and filled with testosterone the brute force solution seemed best, so I
>found some rubber bands and a pair of rubber gloves. After twenty minutes
>all that I had done was to work up a sweat and teach my dog some new four
>letter words. Then I reread Moose's post - - tried lighter rotational
>pressure and varied between pushing the filters together and pulling them
>apart while twisting. After less than 15 seconds there was an audible click
>and the were free!
The audible click was the little weld breaking.
A semi-related war story: In the 1970s, some of my friends were motorcycle
bums (or at least looked it; it was good for attracting girls). One of them
had a Kawasaki, and the cover protecting the alternator was held by three or
four aluminium #2 phillips machine screws directly into the aluminium housing,
so it was aluminium on aluminium, under high pressure. The theory was that if
the screws were steel, electrogalvanic corrosion would destroy the screws.
Those aluminium screws *always* froze, and aluminium screws are not strong
enough to just force them to turn; the head would instead twist off. My
solution was to use a hammer-driven impact wrench with a brand new (and thus
sharp) screwdriver bit, driven by a two-pound drilling hammer. It always
worked. The shock of the hammer blow broke the weld exactly at the moment the
impact wrench forcibly turned the screwdriver bit, and the screw came free with
a resounding "crack!", not just a polite little click. The rapid mot!
ion after the break prevented re-welding, and the screw was undamaged. The
aluminium screws were then replaced with well-lubricated stainless steel. In
some cases, one had to install helicoils in the housing to repair threads
damaged in prior, unsuccesful attempts. The hardest thing was to get people to
leave those aluminium screws alone until the right equipment was at hand, and
they would mangle the screwheads with their attempts to remove the screws with
an ordinary screwdriver.
I suppose the photographic equivalent would be to use one of those plastic
wrenches on the filter and put the filter under unscrewing force while smacking
with a wooden mallet a piece of wood pressed against the face of the filter
ring. But I've never had to do anything that draconian. It doesn't seem like
a good idea; cameras are not built like mototcycles.
Joe Gwinn
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