[asking for help] objective lens stuck in the wheel

[henrymyf]

Hi everyone, I'm new here. I have a problem to solve:

I found a 5-lens-wheel in my collaborator's drawer, which is very poor maintained. Apparently, these 5 objective lenses are stuck on the wheel (due to extensive use and liquid soak), and the wheel is broken from the microscope. Someone must have tried to abandon the wheel, while releasing those lenses but failed. I searched online and found that maybe some oil and solvent could loose the thread? But I have no idea how to perform that.

I can tell that these 5 lenses are all very expensive (at least to me), so I really prefer to reuse them instead of just letting them sitting in a messy drawer. So please comment on my options. Thanks!

Henry

[PeteM]

A drop of a solvent oil such as "Kroil" can be applied at the seam where the lens meets the turret. Let it soak into the space between the lens and turret overnight. Even a solvent like lighter fluid (naptha) can help a bit.

I'd start with just the lowest power lens (4x?) and proceed one at a time as you gain experience. Be sure not to let the penetrating oil get near any lens surface.

There are soft grip pliers meant for aircraft connectors. These are like arc-joint pliers but have soft surfaces to grip cylindrical bodies. The can be used low on the lens; again starting near the 4x where you have some space (next to the empty nosepiece hole).

Hopefully that will do it. If not add another drop of oil and very carefully heat up just the turret so it expands slightly around the lens. Let it sit again. Then more heat and try again to remove the lens.

You can apply heat with a hot air gun with a fine focus attachment. Heat just the turret, not the lens barrels. The oil should penetrate a bit further, the metal expand a bit, and lens able to move. Sometimes it helps to attempt to tighten then loosen thread a bit, back and forth, if the lens doesn't simply come out counter-clockwise.

A shame those lenses were treated so badly.

[henrymyf]

A drop of a solvent oil such as "Kroil" can be applied at the seam where the lens meets the turret. Let it soak into the space between the lens and turret overnight. Even a solvent like lighter fluid (naptha) can help a bit.

I'd start with just the lowest power lens (4x?) and proceed one at a time as you gain experience. Be sure not to let the penetrating oil get near any lens surface.

There are soft grip pliers meant for aircraft connectors. These are like arc-joint pliers but have soft surfaces to grip cylindrical bodies. The can be used low on the lens; again starting near the 4x where you have some space (next to the empty nosepiece hole).

Hopefully that will do it. If not add another drop of oil and very carefully heat up just the turret so it expands slightly around the lens. Let it sit again. Then more heat and try again to remove the lens.

You can apply heat with a hot air gun with a fine focus attachment. Heat just the turret, not the lens barrels. The oil should penetrate a bit further, the metal expand a bit, and lens able to move. Sometimes it helps to attempt to tighten then loosen thread a bit, back and forth, if the lens doesn't simply come out counter-clockwise.

A shame those lenses were treated so badly.

Thanks PeteM. Very detailed advice. I will try it slowly, as I don't want to damage any of the optical lens. If I got them out, I think I can have these lenses, as the collaborator already bought new ones..

I agree that it's shameful to have the optical hardware kept so poorly. I'm a new PI, and I'm about to make order on new microscopes (still deciding between Nikon and Olympus), and I certainly don't want my microscope to be treated like this in the future.

Will update on any progress when done. May need some time. First thing is to get some Kroil or naptha solvent, and a pair of soft grip pliers.

[zzffnn]

henrymyf,

In case you have not noticed, those are Olympus infinity corrected objectives, so you would want to use them on an Olympus infinity corrected scope. Don't use them on a Nikon or Zeiss scope; you will get a decent image, but it may not be a good one.

[wporter]

I have had luck using just plain acetone to break free objectives from turrets. A single drop usually works, and takes effect immediately. If it doesn't work, try the penetrating oil (you can even make your own by mixing acetone 50-50 with automatic transmission fluid), but use less than a drop and just enough for it all to be sucked by capillary action into the crack (otherwise it gets all over everything). Let it sit for 10 minutes or longer, then try turning the objective.

The connector pliers mentioned are often very useful, but have the disadvantage of having polyethylene jaws, which can tend to slip. The tendency then is to squeeze harder, which can lead to deformation of the object under attack. To overcome this, get one of those thin silicone pads that are sold as jar-lid-grippers/openers, and cut a 1" wide strip out of one. Wrapping this strip around the objective will both help the grip and prevent damage from the pliers. You can even wrap the strip (folded over) around the objective like a strap-wrench (q.v.) and try to bust it loose by hand.

[apochronaut]

I stay away from solvents, as much as possible but if used, only a tiny drop is necessary at the seam.

Before I would resort to solvents though, I would try this method. It is similar to the soft jaw plier method but exerts less localized pressure on the barrel, has better surface area contact, exerting at least as good a grip. It even separates really frozen 100 year old objective sections, completely clogged with verdigris, by using a longer strap and counter screwing the sections.

Find an old leather strap, from a purse,shoe, camera strap between 1/8 and 1/4" thick. Usually one side has a suedey nap to it still and you put that side around the barrel, wrapping the leather strap tightly around the objective, with the two ends facing away. Then put the deeply curved jaw section of a pair of curved jaw( 5WR,7WR,10WR,7CR AND 10CR) vice grips right on the snug belt and loosely tighten the vice grips, with the knurled tension adjustor onto the belt as tight as you can with your fingers. You will need to start with about 3/4" of thread showing on the tension screw. The little 5WR ones are the ones I use but any of them work well, if there is enough room. For really stubborn smaller smooth cylinders, the 10 inch are a little better because the curvature of the jaw is more extreme and there is more leverage applied with the tensioner, while the jaws are closed.
Once snug and nice and centered on the belt; give it a try. If the belt slips, open the jaw slightly and tighten a bit , clamp and try ...and again if needed. It usually takes only a little clamping force to get results.

Don't just clamp down on the barrel with the vice grips without adjusting the jaw width so that they only lightly impress upon the leather.

Curved jaw pliers work too but vice grips provide a more secure pressure and are more easily adjustable to increase the pressure predictably.

[Charles]

Another alternative to the leather in the above is rubber. Rubber grips very well.

[MicroBob]

Here is an image of a powerful objective wrench. You will have to make it to size at halfway close tolerance, preferably on a lathe. The last step is to cut the bore open. 4-6mm aluminium sheet metal is just fine. Since your objectives are worth a lot it would pay to have a machinist make the wrench. When you turn the revolver you might be able to access the thread from the back. You could apply some oil or mixture as advised from this sitde too. I would suggest to use a screwdriver tip or toothpick to apply the tiny amount needed.

Bob

[apochronaut]

Another alternative to the leather in the above is rubber. Rubber grips very well.

yes, good point Charles. i have used rubber in the past too. it needs to be a fairly dense type and fairly thick. thicker than the 1/8" minimum i set for leather, otherwise it can tear, if the objective is really seized in. the jaws could settle into the metal and scratch or even dent them, and you won't necessarily notice that until a little too late. one of those flat bungee straps ; yes, an old inner tube; no.

not a big fan of metal on metal for removing objectives. one slip and the shroud will be irreparably scored or scratched.

[75RR]

+1 on the rubber for grip
and "the silicone pads that are sold as jar-lid-grippers/openers"
also note that damp leather grips better than dry

[coominya]

I successfully removed one using vice grips and a wrap of rubber around the objective. I liked the fact that I could vary the pressure on the vice grips and 'dial' it up slowly with no danger of applying too much extra inward force while applying the circular force needed to undo it. The grips come in all sizes and having a few here I used one that had a curved set of jaws that closely matched the curvature of the objective to spread the force as equally as I could.