How to disassemble a Mir 1 lens???

Hello all,

I have a M39 Mir 1 lens (alu) and I would like to change the grease as focussing is hard and uneven.

I tried to access the helicoid by removing the focussing ring but it didn't help me much; I still figure out what to remove next...

Like many other lens, is the first step to remove the optical group from behind to access the helicoid?

Thanks a lot.

Nicolas
If you were a "Mir" you would not be an "Gelios"----- But it is easy to open a Mir.
In the mounting side around the rear element which has a small assimetrical sunshade, there is an external nut holding all optical system.
With a spanner wrench careful remove it. The optical block will be free from focusing thread system. Do not loose the spacing washers!
Use WD 40 or similar or even lighter fluid. Relub with common machine oil everything will be OK.
Good luck!
LP

Hello Lius,

I tried to remove the rear nut but it is so tight I nearly twisted my spanner! I disassembled once again the focussing ring, put the lens to minimal distance and removed all the grease I could. From the back, I poured 2-3 drops of alcohol where should be the helicoid and the miracle happened!. I can now focus with one finger and resistance is now even.

I would have prefer to remove the old grease but it works fine without further disassembly. I might try later with a beefy spanner...

When you come to a tight spanner ring you may have to put a small drop of acetone near the threaded part then try. Be careful not to get any on the rear element. I use G300 silicone spareingly on the threads. Don

ZORKIE'S Survive

Gelios
As Digillete said acetone is good but some solvent is also useful.
Alcool in helicoids are a no good choice once may it corrode aluminium. Try to use some oil drops to prevent such corrosion.
Regards
LP