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Now it's time to lube the rigid I-50......
Old 09-03-2005   #1
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Nickfed is offline
Join Date: Aug 2005
Location: Dee Why NSW
Posts: 367
Now it's time to lube the rigid I-50......

I throw this into the great information mine, for the benefit of newbies to the FSU maintenance game..........

The focussing of the rigid Industar 50 is no more sophisticated than the Elmar family, it's just that Krasnogorsk took a little bit of trouble to conceal that fact.

The focussing ring, the one at the front with the distance and aperture scales on it, is retained on the lens barrel by three small grub screws. If these are loosened, the ring can be removed forwards. There is no need to remove the screws completely and, being steel into aluminium, they are not likely to be very tight.

Once the ring is off, all is revealed. The lens barrel has a perimeter flange with two pins in it which limit the rotation by coming up to another pin in the main body. There is a relief in this flange to enable you to get a screwdriver into the stationary pin. Note that when the lens is in the infinity position it is almost but not quite screwed home in the main body. While the focussing thread is multi-start, I don't think it's necessary to mark anything. It's obvious when you have the right one and there is about a one-in-four chance you will get it first time.

Once the single pin is removed, the lens barrel screws right out. The threads can now be cleaned with methylated spirits and a toothbrush. The clean threads can now be lubricated. I used Sil-Glyde (American Grease Stick Co, Muskegon MI).

On assembly, test that the lens almost screws home at infinity. You do not need to put the pin in to see this. When satisfied, replace the pin and screw the lens to the infinity position. Then replace the focussing ring and align the infinity mark with the red arrow. Do not overtighten the little grub screws.

That's all there is to it. Dead easy......In summary, the only parts that need be removed are the focussing ring and the single pin in the outer barrel. I made the mistake of starting at the back and working forwards - all un-necessary.

I did not attempt anything on the aperture ring. It was only the slightest bit stiff and I would rather it that way than loose, particularly as I use a clamp-on Leitz lens hood on it.

FWIW, the female focussing thread screws into the main body i.e. the back section that screws into the camera, and is locked by a single grub screw. The ring with the depth of field scale is fixed to the main body by three grub screws and is little more than a dress ring, separate only for ease of manufacture. I don't believe it is necessary to undo these, ever.

Note also that on my lens, the flange with the two pins in it that form the focus stops has another thread in it. I don't know why it is there. Nothing goes in it.

Last edited by Nickfed : 09-04-2005 at 05:26.
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