Disassembing Steinheil 135/3.5 Auto-D-Tele-Quinar -diaphragm

[peoplemerge]

I'm new to lens repair in general but this has become a delightful hobby! The helicoid needed a vigorous clean and relube, and I thought the aperture needed adjustment to open fully wide.




Reading http://forum.mflenses.com/steinheil-quinar-135mm-version-f2-8-vs-f3-5-t68891.html, is this in fact a feature* of the lens design which is not repairable? (*as an engineer, part of my mandatory training by the marketing department is to call this type of thing a "feature" than a "flaw" )

Or it a weak spot of the design that affects a high proportion of these lenses?

If there is no definitive answer on the subject, I'd like to proceed with the repair, but I'm having trouble getting to the diaphragm.

Without applying excessive force, I can't get it apart, even with a spanner wrench. I see these set screws:




I don't see how removing them will unscrew that barrel and I'm worried it could cause the diaphragm to unravel. Accessing the assembly from the front seems much harder, and will probably require an investment in rubber lens moulds. The interior glass is totally pristine, so this is really a last resort.

Edit: I also noticed http://forum.mflenses.com/steinheil-bv-tele-quinar-200mm-f-4-5-preset-m42-t64522.html describing a different focal length lens, and the photos referred aren't up any more. Just so you know I did my homework

[peoplemerge]

bump... Feedback on whether the aperture shape looks the way it did from factory?

[calvin83]

[peoplemerge]

calvin83: thx!