How to disassembly old brass Tessar 400mm f4.5

[blanc-negre]

I have old brass Zeiss Tessar 400 f4.5 lens, there is some fungus inside the lens, and I would like to clean glass, polish barrel and finish with lackeur.
The thing is that I dont know how to disassembly it, what should be unscerw as first?
Could someone help with advise ?





BR
Tom

[Steven Tribe]

This looks pretty early as it has a mm F scale showing iris diameter.
The front lens cell (two lenses) unscrews under the text.
The rear lens is the same anticlockwise screwing - this has two lenses cemented together (I hope!).
What you call fungus could be glue separation in the rear cell and just dirt between the two front lenses.
Re-finishing the brass can be done - the worst problem is pitting in the brass where the zink has been leached out.

[wallrat]

I would use a strap wrench to prevent damage to the barrel. It appears from the photo that the barrel unscrews at the top. If not, it may be that you need to remove the retainer ring.

HTH,
Bill

[Michael E]

Tough to tell you exactly without the lens in hand... You can definately remove the front and rear groups by unscrewing the outer ends of the barrel. If you are lucky, you get all the gunk out without further disassembly. So far, you don't have to worry about the correct assembly afterwards.

To remove the front elements completely, sometimes there is a threaded insert from the inside of the removed front group. Simply unscrew it. Otherwise, you have to remove the retainer ring from the outside (filter thread). This will get get messy, as the thread and the ring seem damaged. Plus, you have to be careful to replace the element and the ring correctly. Otherwise, the optical system might be misaligned. Accidentally reversing an element is very common, too...

Good luck!

Michael

[blanc-negre]

Thanks All for your help,
I will try with strap wrench, to unscrew barrel at the top, hopefully no need to unscrew retaining ring which is damaged

It is early Tessar lens from 1907,
looks similar like this from catalog:



cement between the lens looks ok, but there is small dot of fungus, and some haze.
I hope I can handle with this work.

Many thanks Guys

[Steven Tribe]

I have yet to see fungus on uncoated lenses which doesn't just wipe off!
2 people doing the unscrewing exert more than twice the torque of a single person.

[Hermes07]

Not saying it can't be done, but I have tried to unscrew the front group of a big tessar in the same design of barrel before using a pipe clamp and a steel threaded rod. the steel rod bent, the front group didn't budge. Either there's a small retaining screw somewhere I can't see or I'll need to hire a circular saw.

[blanc-negre]

I have made two "strap wrenches" from old transmission belt and some wood pieces. It works, front group unscrewed !

[E. von Hoegh]

Not saying it can't be done, but I have tried to unscrew the front group of a big tessar in the same design of barrel before using a pipe clamp and a steel threaded rod. the steel rod bent, the front group didn't budge. Either there's a small retaining screw somewhere I can't see or I'll need to hire a circular saw.

Penetrating oil, "Kroil" is the best, "PB Blaster" is great though.

[Hermes07]

Need to get another bottle of Kroil. Ran out a while back and no-one sells it over here anymore.