I got that lens cheap on eBay, and it had a rather sticky diaphragm, so since I also got a much nicer Pancolar 50mm f1.8 with a similar problem I decided to train my hand at the Tessar first.
I tried to make a complete nomenclatura of the various bits and pieces encountered, and where they are in each of the pictures.
I used a Sigma 28-135 Macro for the first few pics, then gave up on it and used the Zeiss Flektogon 35mm f2.4 renowed short focus distance to do all the better ones.
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To take appart the lens I started at the bottom, I originaly tought the blades were easily accessible from there.I was wrong, but removing the bottom was a necessary step anyway.
You can see the first layer of the inside.
This is the inside barrel 6. Here we can have a good view of the apperture mechanism from 2 windows : one of them is for the automatic apperture control, the second is for the manual control.
One thing to note is that the screws 13 help to position 14 properly, there is some tolerance here and you'll have to remount these in a position where 16 doesn't get stuck or jumps out of it's groove later on.
This is from the other side, you can see 10 that is screwed on 18 and is the automatic apperture calibration. You can remove it later, but be sure not to remove the small screws on it, you'd have to redo the infinity calibration etc!
Now from the rear you can see and touch the iris blades. But thats all, thats all you can do from the bottom.
Now we need to attack from the top !
You might have to use quite some torque to get that done, I used two towels to get a bit more grip.
You can also at this point:
Now we can see whats in the front.
Once again 24 was very very tightly screwed, I hade to use a pincer and quite some force to get it to unscrew.
Without the middle element, at last you get access to the iris apparatus.
Next is a big view of all the bits and pieces at this stage, before we attack the iris proper.
Now its time to remove the iris.
An interesting point here is that the screw holes for 28 are not in an equilateral triangle, which means you can't go wrong when putting 29 back, Clever!
And there we are, the whole of the lens has been taken appart. Now you dan do the cleaning of each piece.
Once it's clean, I practiced on the table how the heck was I suposed to put back the whole thing together. So here is the iris back in shape, on paper.
Puting it back inside is a bit harder, but you can use tweezers and the side windows in the chamber to position back the blades they should.
The rest of the reinstallation of the front part is very straightforward.
Here is the lens almost completely mounted. Rescrewing the mobile element in the focusing thread can be a bit dodgy. be SURE that you can still focus to both ends after you reinstall the guide. If it doesn't, remove the focusing barell, turn it 1/3 and screw it again using the next thread position.
And here is the result, a nice, clean, snappy iris on a nice, clean "as new" old tessar!