Olympus CX31 stuck objective

[coprinus]

Hi,

I have an objective that is stuck in the revolving part of the microscope.
Even if I apply considerable force, I am not able to unscrew it.

I bought the Olympus second hand and I was never able to remove it, so it is probable stuck for a considerable amount of time.
If I remove the head of the microscope I can access the objective from the other side.

Does anyone know a trick how to remove this objective without damage to it or to the microscope?

[dtsh]

Anytime you apply more force than hand tight there's a risk of damage, that said...
In general if you can grab it with a small strap wrench or a pair of pliers that have a soft-jaw or something between the jaws and the objective surface, such as a piece of leather, rubber, etc to protect the finish you might be able to get enough leverage to loosen it. The hardest part IMO with things like that are managing to keep a good grip without crushing or marring. I wonder if it was cross threaded at some point?

[Hobbyst46]

A relatively safe approach is cooling the objective then trying to unscrew it. If you can wrap it up with a cold bag of some sort, or even just a damp cloth right out of the freezer, then try to unscrew it before the cold spreads to the turret. The idea is a slight shrink of the male thread.

[PeteM]

If truly stuck, you might start by removing all but the the one stuck objective and the turret. I'd assume, for the CX, that something like 3 screws attaches it. Then you'll have just the nosepiece and the stuck lens, easy access, and no fear of damaging anything else.

It helps to get a tiny bit of solvent right at the threads. Even lighter fluid can help, something like Liquid Wrench or Kroil better. Apply sparingly right at the joint. I heat up the turret just a bit with a pencil type hot air gun before and/or after. A hair dryer is fine, but you want the heat on the nosepiece, not the objective. Idea is to get just a bit of expansion. A couple cycles can help, trying removal in between. It takes time (even overnight) and a bit of space (thermal expansion) for penetrants to work their way into the threads.

After that the strap wrench or soft jaw pliers. Here's one type, with soft jaws for holding connectors, that works pretty well: https://www.ebay.com/itm/Diamond-Tools- ... ondition=4

You can also wrap several layers of masking tape around the objective and (usually) remove it with regular arc joint pliers with a bit of care and not damage the finish. There are also cheap rubber pads to mount on regular serrated jaw pliers and all the other suggestions of dtsh, above.

For truly stuck objectives, I grab the objective end in the right sized lathe collet, which is even more secure. So far, never an objective that remained stuck. One of the nice things about brass is that it doesn't gall. It can get seriously corroded, though.

For even greater thermal difference, the combination of heating the nosepiece and cooling the objective could work; though the pencil type hot air guns are quite cheap and easy to use.

[coprinus]

Thanks a lot for the tips, I let you know it it worked

[coprinus]

It worked !

I removed the non-stuck objectives and the microscope head.
I could not remove the turret. On the CX31there is a single central screw located on the outside between the objectives. You need a short screwdriver with a large tinny blade that I did not have.

I did:
- cool the stuck objective with a moist cloth frozen in the deep freeze.
- heat up the turret with a hot wet cloth in a plastic bad that I did put in the microwave.
- applied additional heat with the hairdryer
- used pliers around the frozen cloth but the objective did not move.

Finally I applied some liquid silicon oil on the seam between the objective threads and the turret.
Together with more heating and cooling and waiting a while, the objective came loose with applying a little force from the pliers.

Thanks a lot for the tips.

[Hobbyst46]

...I could not remove the turret. On the CX31there is a single central screw located on the outside between the objectives. You need a short screwdriver with a large tinny blade that I did not have.

1. Great ! glad the problem was solved.
2. BTW, perhaps the central screw is a righthand screw, so, unscrew by clockwise rotation. Irrelevant at the moment...

[PrecisionInstruments]

Central screw is standard thread, though plenty of factory lock tight applied. The screw is easily damaged when trying to undo, unless plenty of heat by flame has been applied. The whole top arm is required to be replaced if screw gets damaged.

[coprinus]

Hi,

Thanks for the warning.
Another topic:
Did you ever disassemble the stage of a CX31, in order to grease the ball bearings?

[PrecisionInstruments]

If you are referring to the X & Y linear bearings, I do not bother disassembling them. I do flush the old lubricant out and replace with new by feeding in from ends. Racking the stage back and forth will drag it in, you only need a very small amount.
I do take the controls apart for replacing lubricant also.