cleaning Jupiter-8 50mm

I have a Jupiter-8 50mm lens in Leica Screw Mount which
has oil on the f-stop blades. I've managed to unscrew
the rear lens cell assembly which allows cleaning of the
back of the blades, but I am at a loss at how to get to
the front.
I can't see any notches or other ways of removing the front
cells.
Any advice appreciated. Thanks...

--
Robert D Feinman
Landscapes, Cityscapes and Panoramic Photographs
http://robertdfeinman.com
mail:

Robert Feinman wrote in
:

I have a Jupiter-8 50mm lens in Leica Screw Mount which
has oil on the f-stop blades. I've managed to unscrew
the rear lens cell assembly which allows cleaning of the
back of the blades, but I am at a loss at how to get to
the front.
I can't see any notches or other ways of removing the front
cells.
Any advice appreciated. Thanks...

Here's what I did (note complete lack of correct technical terms)
Remove the setscrews in the ring with the f numbers inscribed on it and
screw the ring inwards, revealing the setscrews retaining the outer ring
that filters go on. Undo those and remove both rings. If I remember right
it was no problem to get the optics out, but the funnel shaped assembly
containing the aperture mechanism would not budge. From looking at the
backside of the lens assembly it was clear that the aperture assembly was
threaded in, so I cut two slots on the front edge of the projecting
aperture assembly to fit a thin ruler, which I then used to unscrew the
assembly.
BJ

In article , Robert Feinman wrote:
I have a Jupiter-8 50mm lens in Leica Screw Mount which
has oil on the f-stop blades. I've managed to unscrew
the rear lens cell assembly which allows cleaning of the
back of the blades, but I am at a loss at how to get to
the front.

Why? The lens does not have to stop down quickly, it's on a rangefinder
camera. The oil won't hurt anything and it will keep the blades from
sticking or rusting.

Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
IL Voice: 972-544-608-069 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838
I may be an old fart, but I'm a high-tech, up to date old fart. :-)

In article ,
says...
In article , Robert Feinman wrote:
I have a Jupiter-8 50mm lens in Leica Screw Mount which
has oil on the f-stop blades. I've managed to unscrew
the rear lens cell assembly which allows cleaning of the
back of the blades, but I am at a loss at how to get to
the front.

Why? The lens does not have to stop down quickly, it's on a rangefinder
camera. The oil won't hurt anything and it will keep the blades from
sticking or rusting.

Geoff.

Because turning the f-stop ring moves the focus position at the same
time. So I either have to keep turning until I reach the focus limits
or I have to hold the focus ring with another finger while adjusting
the f-stop. It also makes trimming the exposure a pain after the focus
has been set.
All of which makes quick shooting of people on the street slower than
it should be.

--
Robert D Feinman
Landscapes, Cityscapes and Panoramic Photographs
http://robertdfeinman.com
mail:

Robert Feinman wrote:

Because turning the f-stop ring moves the focus position at the same
time. So I either have to keep turning until I reach the focus limits
or I have to hold the focus ring with another finger while adjusting
the f-stop. It also makes trimming the exposure a pain after the focus
has been set.

Sound like the ring is gummed up, not the blades. I had the opposite
problem, in that it moved too easily and I was able to fix it by removing
the three set screws and then screwing it in to expose the thread. Whereas
I added grease to slow it down, you can probably solve your problem by just
wiping the threads with a cloth dabbed in WD-40 or paint-thinner.

--
Dominic Richens |
"If you're not *outraged*, you're not paying attention!"

I found on mine that the main contributor to drag on the aperture setting
was the grease between the stationary and moving conical parts of the the
aperture mechanism. Finding an appropriate grease and applying it in the
correct amount took a couple of iterations.
BJ