Help for dismantling Leitz objective

[Leitzcycler]

I bought for-parts-objective and would like to clean it. It has some salt precipitate-looking dirt behind the front lens (between two outer lenses). So I have to dismantle the front lenses hopefully not touching the inner lenses in the system. I managed to turn the outer sleeve off. However, the inner sleeve (A in the figure) seems to be either very tight or cannot be released.

1. Is it possible to take the front lens off by removing the sleeve A? If not, do I have to unscrew the lock ring in the upper side of the objective (RMS thread side) and dismantle the whole lens system to release the front lens? How can this be done safely so that I get the right orientation of the lenses when packing after cleaning?
2. For what purpose are the holes marked B? I can see nothing like a notch for a screwdriver inside.
3. What is the best way to clean the inner lenses and what kind of solvent I can try? Is there some solvent that must not be used to prevent the lamination from dissolving? The inner lens surfaces must not be wiped with material of any kind, right?

[abednego1995]

That objective has a safety spring nose, so it's essentially a lens holder inside a outer tube pressed against a forward flange with a spring.
You have to access the inner lens assembly from the rear (mount side) loosening the ring screws.

Though you'll eventually get inside to the elements you suspect to be defective, this being a Fluotar you'll probably never get it assembled to original state.
You'd need a collimator to align each cell retaining the lens elements (by rotation, since each lens has already be trued against the cell itself, but not other cells.)

If it isn't horrible already, I'd leave it as is and get another good copy.

Cheers,
John

[Leitzcycler]

Thanks! This is practically useless now and there is nothing to lose. I bought this partly for fun and experience (of course hoping to get it cleaned again). I try to dismantle and mark the lens orientation and see what happens.

Tips for cleaning the lenses are still welcome.

[apochronaut]

I would agree with John, regarding this one. It will be a difficult objective to reassemble to a condition that would pass an o.e.m. quality control inspection.

However, if it is no good otherwise, give it a try. With respect to the collimation between cells. A trick is to disassemble the objective with great care, taking the time to scibe the cell/shim stack as it comes out, as well as making a registration mark on the barrel. That way, it can be reassembled in the same rotational registration as it was originally set to at the factory. Objectives, used to have this done at the factory, so reassembling to the original registration wasn't that difficult. Newer objectives, often do not have any registration marks, so it doesn't hurt to make some. I am not sure about this one, having never had one like it apart but I have had a Leitz 170mm tube 100X 1.32 planapo apart and the design looks very similar. For sure, more modern manufacturing techniques have increased the precision of the individual components but where cemented doublets or triplets exist in machined cells, it would seem that some centering has to be necessary. In this case I would think for sure, otherwise centering adjustment screws would not have been included in the design. You will need to reassemble it to conform to the existing set of the screws, because you have no way of determining collimation , if you choose to adjust the setting of the cell stack.

In answer to some of your questions.
1) Bearing in mind that I have not had one of these apart, based on the look of the design, I would suspect that the front lens cell can be removed by removing the front collar. This is not as easy as it sounds usually, because over time with an oel immersion objective everything gets gummed up with dried immersion oil. The front collar will likely be very difficult to unthread. I use two thin belts of full grain leather wrapped around both the male and female threaded parts and grip them to those parts with two pairs of 6" vice grips. The vice grip tension must be just so it grips the leather and the leather the smooth surface underneath. Overtightening of the vice grips can be dangerous because it can deform the collar. Once the collar come free, use only minimum tightening or your fingers. Putting a a drop or two of solvent, a varsol type, lighter fluid etc., at the thread seam a day in advance and standing the objective up so gravity can help will aid the process. Once off, the front lens cell is a press fit and will also be gummed up. Usually there is enough protruding that the belt/vice grip technique can be employed to twist it out of it's sleeve. Solvent maybe too but very little and only if required. In this case try isopropyl, although it is much weaker.
Your description of the interior contents are not too auspicious. I have seen this type of thing before and it has been some type of degradation product of the lens cement used. Possibly it is not even repairable, except by the application of gentle heat, maybe.

2) collimation adjustors. They are often plugged after setting.

3) If the deposit in there turns out to be some type of loose debris, on the surface, and can be removed, see if you can blow it out and away but almost for sure there will need be a cleaning of the relevant surfaces. I would use an isopropyl/water/blend with a tiny amount of detergent added. Maybe 1oz./3 oz. plus 2 or 3 drops. Clean with that and swabs, then rinse with a quick wipe with isopropyl.
Some lenses had a softer coating on the interior lenses, so it could have delicate surfaces. Not sure about Leitz of this vintage. The old 170mm planapo did not have soft coatings. I removed the coating on one surface of an old 160mm Reichert objective once. The objective was restored to what I would call good to excellent performance, nonetheless. It had been dreadful before and I had no benchmark with which to compare it's clean state to. The lack of a coating on one surface was likely of significance but minimally so. It certainly was an improvement over the before state.

[Leitzcycler]

Thank you so much for this valuable information! I highly appreciate your effort in sharing your knowledge.

Mika