Repairing a stuck spring-loaded 100x objective?

[Polymerase]

I recently acquired an Olympus splan apochromatic 100x objective with an iris. The optics are clear and working well, but the springloading mechanism of the front lens is not working. It won’t budge a micrometer, and broke an important slide while I tested it.
I’ve browsed the forum to see if anyone could point me in the right direction, but haven’t really found anything too useful. I am not competent to take the objective apart, and would rather not attempt to do so.
As I understand, the likely culprit is that lubricants or excessive immersion oil has hardened between the outer and inner barrel, and prevents the lens assembly from being pushed into the barrel. I’ve tried to dissolve this by injecting 95% ethanol with a 26G needle. No success. Tried xylol. Still no change. I am uncertain whether I’ve succeeded in getting the liquid to enter between surfaces, as the needle hardly gets between them.
I’ve seen references on the forum to the use of “lighter fluid.” This is a very unspecific term, and I hope someone can explain what it is supposed to be. Butane? Kerosene? Gasoline? It is obviously some hydrocarbone in terms of chemical properties, but I am hesitant to try until I get more specific advice. And I would rather not use something that could dissolve the cement keeping the front lens in place.
I hope someone could point me inthe right direction. The objective is in such good shape, it would be a pity to throw it out. But I can’t have it break my specimens on a regular basis.

Any suggestions?

[Hobbyst46]

1. Gas lighter fluid is likely butane or mostly butane - certainly not kerosene
2. You might try gentle heating of the objective in an oven at 30-35 degrees celsius for dissolution.
But, since you already tried Xylene to no avail, possibly a tiny solid dust particle is the culprit and not hardened grease.
BTW, a common salt crystal will dissolve in water, not in xylene and probably not in 95% ethanol - unless one floods with ethanol, which you did not.
Disassembly is the direction despite the risks, IMHO.
Maybe this post will help.
https://www.microbehunter.com/microscop ... ir#p135833

[Polymerase]

Thanks for clarifying the butane part!
I can put the objective in an incubator at the temperatures you suggest. Is it safe to immerse it insolvent? I am afraid that could damage the front lens cement…
Mentioning water - wouldn’t that be harmful to the internal parts of the objective?
I absolutely agree with the solubility comments you made. But if the retraction os due to particles, it is likely more than one, as it seems uniformly stuck. There is no movement in any direction, like it is glued to the barrel.

In short - is it safe to immerse the bottom part of the objective in water or solvent? And then heating it?

Disassembly would be a last resort. Luckily I have another working 100x splan apo. This one came with a microscope I eecently bought, and thus is no great loss if I can’t make it work. But redundancy is always good!

I’ll have a look at the thread you linked to.

[PeteM]

Liquid lighter fluids, such as Ronsonol, are a commonly used and relatively safe solvent. Most come in an applicator bottle that's fairly convenient. The MSDS descriptions have changed a bit (and are a bit vague), but the two formulations I've used don't leave a residue. Far better than, say, WD40.

As Hobbyist46 said, heat can sometimes help loosen up hardened immersion oil. Once you get it moving, a solvent can sometimes be more effective.

It's best if you can remove the outer lens cover to get a clean look at the spring-loaded mechanism. The lens elements are usually in a brass barrel, spring-loaded at the back, and sliding in the outer brass barrel with a screw guiding it in a keyway in the outer barrel. It's often possible to remove the entire lens barrel, thus preserving the original careful spacing, centering, and cleanliness of lens elements.

I don't have experience with an Olympus SPlan Apo 100x oil iris objective - and the iris will add a complication - but if you can find a lens diagram, it should show you how to get the outer cover off. Maybe how to remove the entire lens barrel. From there, you'll be able to see and fix the problem rather than try to feed solvent in from the tip. If you do use solvent, no need to get it on the lens element. It goes in the tiny circular clearance where the inner barrel slides. That circular clearance is clearly visible in all the Olympus SPlanApos I have (unlike, say Leica DM objectives where the outer shroud has to be removed).

If you can't get it apart, my generally successful kludge has been to put the objective lens up, add a couple of small drops of solvent, and let it sit for a while. Then, carefully apply heat around the outer barrel (avoiding the lens area) using a cheap hot air pencil. Then try to get the lens barrel moving inside. A "shake" might get it down. If balky, I try capturing the exposed end in a lathe collet (very secure, non-marring) and move the spring-loaded barrel back and forth. Use the solvent to get it moving freely. Then, add a drop or two of extremely light oil afterward to keep it (for a while) from seizing up again. Otherwise, the solvent will evaporate, and whatever oil froze it up before will harden again.

It's really best if you can get it apart, remove all traces of oil, and have it move freely without any oil or only the barest traces. In some cases, with damage to the sliding fit, the inner or outer barrel may have to be ever-so-carefully cleaned up with something like 800-grit silicon carbide paper.

Let us know if and how you get it fixed.

FWIW, 100x objectives weren't always spring-loaded. Microscopists probably got in the habit of lowering their 100x objectives until just barely immersed - looking from the side rather than through the eyepieces. Even with spring-loaded objectives, this is what I suggest with kids. When looking from the side, dipping into oil immersion, there's a flash of light when the objective is fully immersed. Careful fine-focusing back away from that nearly-focused point should help avoid breaking slides, even with a stuck spring.

[Polymerase]

I am most grateful for all your suggestions!

Currently, I am applying butane. I am uncertain how much time it needs, and it evaporates rather quickly. How much butane actually enters the slit is uncertain.

I’ll keep you updated!

[PeteM]

I'll be surprised if the butane works. When people advise using lighter fluid as a solvent, it's usually the liquid form.

Most will evaporate. You might even cool the outer barrel, making the fit even tighter.

[Chas]

Cigarette lighter fluid is for wick-based lighters, its a liquid* rather than a compressed gas. one MSDS I have seen says C7 to C9 alkanes ..so heptane to nonane.
It might not be the ideal solvent for hardened immersion oil, but it is very good for freeing stuck threads and re-fluidising dried/hardened grease.
The downside of it is that it evaporates pretty quickly; a drip on a piece of paper becomes invisible after a minute.
So one needs to find a way of confining the liquid to the area of interest, which is quite difficult, and any solvent needs time to penetrate something that is really hardened , maybe a day maybe two.
It can help to break 'into' hardened crud using a fine sewing needle under a stereo microscope, if you can see any.
I have had a few frozen oil immersion lenses, mostly basic things from the 1970's .. lighter fluid alone did not free them (maybe it is the wrong solvent for this job ?) and the last one I had to force the nose in by compressing the objective lengthwise in a vice.(I am not recommending this !) and it went with a bang. The objective's lens was kept away from the jaw of the vice with a nut or an olive.
Do check that the nose of your objective is stuck in the 'out' position rather than retracted, as I have had one that was retracted in and that was caused more by solidified grease and that is a bit of a different problem.
Hard immersion oil seems a bit like cyanoacrylate glue ..it doesnt take much.

* The liquid lighter fluid comes in rectangular tins (the compressed cigarette lighter gas comes in cylindrical ones).

[Polymerase]

Currently, I am not in posession of liquid butane, rather the compressed gas. And I did wonder, whether the cooling would tighten up the jam. On the other hand, the pressure of the gas facilitates getting it into the mechanism - I could see minute air bubbles escape. I was wondering whether I could liquify it by means of a vacuum tube and a blood-drawing cannula, but I haven’t come around to it yet. I don’t even know if it is possible, and probably, it would go into gas phase upon opening the tube.

The stereoscope/needle path is indeed clever. However, when I can’t get a 26G needle in, I doubt a fine sewing needle would do the trick.
The objective is indeed stuck in the “out” position.

No luck with the butane, so far. I’ve put it in an incubator at 35 degrees celsius, and will leave it there until tomorrow, hoping that might give it a little movement.

Updates will follow! I am most grateful for all of your suggestions!

[Polymerase]

FWIW, 100x objectives weren't always spring-loaded. Microscopists probably got in the habit of lowering their 100x objectives until just barely immersed - looking from the side rather than through the eyepieces. Even with spring-loaded objectives, this is what I suggest with kids. When looking from the side, dipping into oil immersion, there's a flash of light when the objective is fully immersed. Careful fine-focusing back away from that nearly-focused point should help avoid breaking slides, even with a stuck spring.

Absolutely! That is how I was trained. But sometimes you get lazy and cut corners. This is the one occasion where I shouldn’t have done that. It is a poor excuse that it was sold as “used - in excellent condition” I should have checked it before being too eager to look through it….

It is the second time in twenty years I break a slide….

[Hobbyst46]

I would suggest to never ever soak or immerse the objective in any liquid, any solvent. If a drop or a few drops do not work, do not be tempted to flood.

[Polymerase]

I would suggest to never ever soak or immerse the objective in any liquid, any solvent. If a drop or a few drops do not work, do not be tempted to flood.

Just as I suspected. Thanks for emphasizing that point! There was something you wrote that made me doubt my instincts. I’d rather ask stupid questions than performing stupid actions. In my experience from teaching, when a student asks a question he thinks is stupid, not only does he get an answer to something he didn’t know - but there are at least a dozen other students who were also scared to ask the same thing. Thus, in essence, no question is ever stupid.

[Chas]

OK, this is a very long shot ; you could try a drop or two of Type A immersion oil (the thin stuff) ? I have just tried some on a hard-to-undo screw top of a Cedarwood immersion oil bottle and it stopped the 'heavy dragging'.
I guess it might take a week or two to soften dried immersion oil.
The old 1970's sprung immersion objectives that I have taken apart had their optics in barrel of their own inside the outer barrel, so as long as you are cautious there shouldnt be too much of a risk of getting the oil into the optics (that said i have quite a few non sprung immersion objectives that have lens cavities full of it! but I guess they might have been heavily used path lab items).

[Polymerase]

No luck with heating over night….
I think it is possible to unscrew the lower part of the housing beneath the iris regulator. Might try it later on, today.
Using immersion oil seems like a rather risky endeavour.

[Polymerase]

Update:

I’ve tried to open the assembly, but have not succeeded. There is a black insert at the back that unscrews easily, but there is absolutely nothing underneath it that can be unscrewed.
I’ve tried unscrewing the distal part, but it is stuck (I think there is a cap in front of the iris, that can be unscrewed, but I am not absolutely certain). Until I know for certain that thos is a threaded cap, I will not exert too much force on it.

Unless anyone knows how to open such an objective, I think I will need to leave it at that.
It’s a shame, as this is a very good (and very expensive) n.a. 1.40 objective.
Luckily, I have another one, but I would love to have one at each of my BHS scopes.

I am open to further suggestions, but have run out of options at this time.

[MichaelG.]

.

I don’t know if it’s available where you reside, but: The most effective penetrating/dismantling fluid that I have found is PlusGas Formula A … this is mostly Kerosene, but seems to have a secret [and very powerful] added ingredient.

https://www.plusgas.co.uk/sga-common/fi ... S%20UK.pdf

On something like your objective, I would first clean any visible joint-lines and then apply tiny amounts of the fluid … watching carefully to see if any is being drawn-in by capillary action. If it is, then continue to apply fluid to those areas.
It makes a very good job of dissolving/thinning hardened greases of most types.

MichaelG.
.

Note: it is counter-productive to use too much fluid … just proceed slowly and carefully.
Note: use it in liquid form … not as a spray [but I’m sure you know that]

[Tom Jones]

Carl Hunsinger has a very complete series of instructional pdf's and videos on maintenance and repair of Olympus BH-2 series microscopes. If you haven't ssen them, the list and links are maintained on Alan Woods excellent website:

https://www.alanwood.net/olympus/downlo ... bh2repairs

They're complete enough I've just finished complete overhaul and regreasing of a couple of BHS's and nine BHT/BHTU's.

Carl has one dedicated to cleaning and freeing-up spring-loaded objectives:

https://www.alanwood.net/downloads/olym ... ky-tip.pdf

The last section is on DPlanApos, which appear to have similar construction to the SPlanApos. While I've just done about a dozen DPlans, which are very easy, I admit the construction of the Apos appears a little (!) daunting and I haven't tried it yet. But since I have a set of DPlanApos and SPlanApos that could use cleaning I'll probably give it a try at some point.

If nothing else it will give you some insight into what you're looking at.

[Hobbyst46]

https://www.alanwood.net/downloads/olym ... ky-tip.pdf

Thanks for this link ! did not know that objective repair was also covered by Carl !

[Polymerase]

Carl Hunsinger has a very complete series of instructional pdf's and videos on maintenance and repair of Olympus BH-2 series microscopes. If you haven't ssen them, the list and links are maintained on Alan Woods excellent website:

https://www.alanwood.net/olympus/downlo ... bh2repairs

They're complete enough I've just finished complete overhaul and regreasing of a couple of BHS's and nine BHT/BHTU's.

Carl has one dedicated to cleaning and freeing-up spring-loaded objectives:

https://www.alanwood.net/downloads/olym ... ky-tip.pdf

The last section is on DPlanApos, which appear to have similar construction to the SPlanApos. While I've just done about a dozen DPlans, which are very easy, I admit the construction of the Apos appears a little (!) daunting and I haven't tried it yet. But since I have a set of DPlanApos and SPlanApos that could use cleaning I'll probably give it a try at some point.

If nothing else it will give you some insight into what you're looking at.

Thank you!

I am aware of this document. However, it does not tell me how to deal with the iris (this specific objective isn’t even mentioned), and I am not confident I am able to put the objective back together if I succeed in opening it. Getting the distal cap off would facilitate things a lot, but from there, I am in “terra incognita.”
I’ll get back to you!

[Chas]

A suggestion; It might be worthwhile (before attempting to take the thing apart) to slide a thin feeler-guage into ( and around) the gap between the 'knurled end ring' and the 'inner optics barrel' to make sure that the two arent locked together by hardened immersion oil. If they are locked together then there seems to be a chance that the screw that that locates the inner optic barrel might be sheared when you attempt to undo the the 'knurled end ring'.
Feeler-guage sets are inexpensive and the thinnest of the blades seem to be around a thousandth of an inch and so might have a good chance of fitting into this gap.

[Polymerase]

A suggestion; It might be worthwhile (before attempting to take the thing apart) to slide a thin feeler-guage into ( and around) the gap between the 'knurled end ring' and the 'inner optics barrel' to make sure that the two arent locked together by hardened immersion oil. If they are locked together then there seems to be a chance that the screw that that locates the inner optic barrel might be sheared when you attempt to undo the the 'knurled end ring'.
Feeler-guage sets are inexpensive and the thinnest of the blades seem to be around a thousandth of an inch and so might have a good chance of fitting into this gap.

This is a very good suggestion!
Now, where would I obtain a feeler-gauge?

[dtsh]

This is a very good suggestion!
Now, where would I obtain a feeler-gauge?

Any auto-parts store should have them as well as a number of other tool outlets.

[Chas]

Amazon & ebay have them too.
They look like this, closed up :

feeler guage closed up.jpg (7.08 KiB) Viewed 2365 times

They look like this when all of the feelers are unfolded (but generally you would only fold out the the feeler that you wanted to use):

feeler guage opened up.jpg (36.73 KiB) Viewed 2365 times

They were used for setting the gap in the contact breaker ('points') that lived under the distributer cap in petrol engines a long time ago