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Industar 50-2 sticky focus
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PostPosted: Thu Nov 13, 2008 4:50 pm    Post subject: Industar 50-2 sticky focus Reply with quote

So my Industar 50-2 showed up the other day, and it's in nice shape, but it feels like the helicoid is dry. (and what you can see of it at infinity focus is certainly dry) It's not stuck, it just sort of binds and frees as you turn it.

What is the collective wisdom on a) getting it apart to lube the helicoid, and b) what lubricant to use?

Thanks-Zandr


PostPosted: Thu Nov 13, 2008 5:00 pm    Post subject: Reply with quote

Use heat resist material to avoid getting oil on blades at summer time.


PostPosted: Thu Nov 13, 2008 6:52 pm    Post subject: Reply with quote

It's very easy to clean the helicoid. It can make a difference and I think that it is worth doing.


PostPosted: Thu Nov 13, 2008 7:49 pm    Post subject: Reply with quote

sichko wrote:
It's very easy to clean the helicoid. It can make a difference and I think that it is worth doing.


Can you point me at a how-to? Or tell me how to get the lens apart? I'm new to working on optics, so cleaning the helicoid on an Industar seems like a good place to start. Wink

-Zandr


PostPosted: Thu Nov 13, 2008 8:01 pm    Post subject: Reply with quote

Give me an hour or so - I may have some pictures.


PostPosted: Thu Nov 13, 2008 9:25 pm    Post subject: Reply with quote

The lens



The focussing ring is held on by three grub screws. These can be loosened or removed to release the ring.



near focus position



infinity focus position



its obvious what to do next



but I chose to remove the bottom ring first



another view



now we've done it



the optical assembly is now turned as if we were focussing beyond infinity. And this is a far as it goes - not very far - a very small part of a turn. This is the position we need as a a reference point when we come to reassemble the lens.



Removal of the optical assembly is easy - you can take reference points on the two parts and, unscrewing very slowly, note where they come apart and after how many turns and/or parts of turns. This is the re-entry point for reassembly. But if you get it wrong you can use trial and error until you get to the position shown above. After removal - three rings and a screw for cleaning. Be careful not to lose the grub screws if they are still present in the rings.



The optical assembly



PostPosted: Thu Nov 13, 2008 10:01 pm    Post subject: Reply with quote

Great tutorial, Sicko! Thank you! I just bought a Industar-50-2 and this infos might come handy some day Smile


PostPosted: Thu Nov 13, 2008 10:08 pm    Post subject: Reply with quote

You can buy special grease for lens helicoils from Micro Tools, but it's very expensive. I tried several different greases and ended up using white lithium grease - it's the best viscosity for smooth turning, which it maintains through a wide temperature range.


PostPosted: Thu Nov 13, 2008 11:06 pm    Post subject: Reply with quote

John,
Thank you for the excellent photos. I'll pick up some white lithium this weekend and have at it. Smile

-Zandr


PostPosted: Sun Jul 29, 2012 2:58 am    Post subject: Reply with quote

Many thanks indeed! Smile


PostPosted: Sun Jul 29, 2012 12:19 pm    Post subject: Reply with quote

Make sure you keep the optics covered when lubing to save a lot of time cleaning afterwards (and possibly removing the coating).