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Industar-50 - how to access the diaphragm for cleaning and repair
Posted By: BigMackCam, 02-27-2018, 11:03 AM

After a request from one of our members, I'm posting this brief "how to" on accessing the diaphragm mechanism of the Industar-50 lens. It's not intended as a complete servicing tutorial, but should serve as a useful starting point for those who need to service or clean the diaphragm.

First, we need to separate the optical and focusing blocks. On the rear of the lens, there's a retaining ring with two holes.



One or both of these holes should have a flat-headed set screw in it (sometimes, they're missing due to previous service attempts). Remove them as necessary, then use a pointed-end lens wrench to unscrew the ring. The optical and focusing blocks can now be separated.





The optical block has two main parts - the tube containing the optical elements and diaphragm, and a front section which includes the diaphragm control ring. The front section is threaded onto the optical tube and held in place by a set screw (this set screw is also one of two that keeps the diaphragm blade "carousel" in place).



Note the size of the gap between the two tube sections for reference during reassembly. Then, remove the set screw. The front and optical tubes can now be separated by unscrewing them.

Now, remove the front optical groups from the optical tube (unscrew the outer ring, and the groups can be removed in one block).





The diaphragm "carousel" is now visible. The red arrow above points to the carousel, which is holding the blades in place. Before it can be removed, another set screw must also be removed.



And now, the diaphragm "carousel" and aperture blades can be removed for cleaning and servicing...

Apologies for the brevity of this short article - it was created in haste specifically to help another member, but I felt it may be useful to others here

Please feel free to PM me if you have any queries!

Last edited by BigMackCam; 02-27-2018 at 11:10 AM.
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02-27-2018, 11:49 AM - 1 Like   #2
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Not anything that I would ever try to do but still interesting and hopefully helpful to the member who requested this. Nice work Mike!

Simple in a way (to this point at least,) but too many fiddly bits for me to lose. Did you then CLA this lens and these images are part of the process?
02-27-2018, 11:56 AM   #3
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QuoteOriginally posted by SSGGeezer Quote
Not anything that I would ever try to do but still interesting and hopefully helpful to the member who requested this. Nice work Mike!
Thanks It's much easier than you think, believe me

QuoteOriginally posted by SSGGeezer Quote
Simple in a way (to this point at least,) but too many fiddly bits for me to lose. Did you then CLA this lens and these images are part of the process?
The Industar-50 and 50-2 are probably the easiest lenses to start working with... there's very little to go wrong. Most other prime lenses are just slightly (or considerably!!) more complicated versions of the same thing... a focusing block and optical block with diaphragm, in two parts that can be separated (usually ). So, once you're confident working on one of these, most other lenses are just an adaptation of the same steps, more or less.

I haven't CLA'd this one yet... it's on my bench, ready to be worked on (I'll probably do it tomorrow). I've done other Industar-50s very recently, though. I find them strangely relaxing now, as I can service them without really thinking
02-27-2018, 12:11 PM   #4
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I suppose I could find a moldy old thrift store manual and try it, with the expectation that it would never function again if I tried. I just have too many hobbies I like to mess around with and can't spare the time to start a new one!

02-27-2018, 04:17 PM - 1 Like   #5
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Thanks for posting! The Industar-50 is such a fun little lens, assembled with the finest Russian sledgehammers!
02-27-2018, 07:51 PM   #6
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QuoteOriginally posted by THoog Quote
Thanks for posting! The Industar-50 is such a fun little lens, assembled with the finest Russian sledgehammers!
Nah, they save those for the camera bodies. They use regular hammers on the lenses .

More on topic, my copy has two silver washers that were between the helical and the lens assembly, do you think those are original, or perhaps a simple modification to allow for infinity focus with M42 adapter on an M39 lens?

From the structure of the lens, I wasn't able to get, how does the aperture ring turn?
02-28-2018, 12:59 AM   #7
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my copy has two silver washers that were between the helical and the lens assembly, do you think those are original, or perhaps a simple modification to allow for infinity focus with M42 adapter on an M39 lens?
It's original. If you check the third photo above, the two spacer washers you describe are seen in place on the optical block, left hand side of the image. In the fourth photo, they've been removed.

Removing one or both of those washers - or adding more - would change the registration distance accordingly.

QuoteOriginally posted by timw4mail Quote
From the structure of the lens, I wasn't able to get, how does the aperture ring turn?
The front section with the aperture ring is threaded onto the optical tube. The two set screws that hold the diaphragm carousel in place run back and forth in a couple of thin cut-outs in the optical tube, and the limits of those cut-outs limits the rotation of the carousel between f/3.5 and f/16. With the front section threaded onto the optical tube and the set screw in place, the aperture ring can be moved back and forth whilst holding the rear of the optical tube, and this will open and close the diaphragm. As such, it's the threads between both sections that need to be cleaned and very lightly lubricated to ensure a decent action for the diaphragm (of course, the blades and carousel need to be clean too, but not lubricated). Some people choose not to lubricate the threads, which results in a very light - but not particularly pleasant - action.

Does that make sense? If not, I can take a couple of extra photos later today...
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