Zeiss Objective Disassembly

[josmann]

Hello all, I recently picked up this Zeiss objective on eBay. In classic eBay lens fashion, this one arrived looking like someone had dumped a bucket of lube into it. I had to do a lot of cleaning to get it into good shape and then I found that it was not parfocal with my other lenses - the spring relief system was bottomed out and seized in place. Today I removed the little pin screw from the side and used some non-marring pliers to twist the lens around in the collar and get it moving up and down again. That released the optic to the bottom so that it's parfocal, but it's still fairly gummy and there is indeed a bunch of greenish grease down in the system visible through the screw hole. I'd like to separate the optic from the outer collar that contains the spring mechanism, but I haven't been able to figure out how to make that happen. My guess is that the color band part is what's holding everything captive. It looks like it's possibly press-fit on or something - anybody know for sure? Is there a secret method to getting into this thing?

Thanks,
Jason

[mineral rob]

The colored ring unscrews from the front. I used two small band clamps (with rubber) but leather should work too. That blue paint layer is really thin so make sure you have a good grip before breaking it free. I am not sure what the next step for clearing out the sticky grease would be.

[josmann]

The colored ring unscrews from the front. I used two small band clamps (with rubber) but leather should work too. That blue paint layer is really thin so make sure you have a good grip before breaking it free. I am not sure what the next step for clearing out the sticky grease would be.

Ah excellent, appreciate the info. It appears whoever assembled this one intended for it to stay assembled - I haven't been able to get this damned thing to unscrew. I'll order some band clamps and see if that allows me to get enough force to break it free.

[mineral rob]

It does take a lot of torque to start it, but then just turns off easily with fingers. The band clamp/rubber strap wrench set I used has one band about 3/4” wide and one about 1/2” wide. A bit big for objectives but worked ok, if a bit fiddly to clamp those small diameters!

[Hobbyst46]

This post of ~ a year ago:

Re: Zeiss achroplan stuck
#14 Post by apochronaut » Mon Jul 25, 2022 10:51 am

Helped me a lot. Using two genuine leather straps, I managed to disassemble a stuck old Zeiss objective.

[josmann]

Well I have tried numerous methods so far, including with the addition of penetrating oil down in the groove, and this thing just absolutely will not budge. I think I'd need an F1 wheel gun to have a hope. Maybe someone disassembled it before me and covered the threads in loctite. I guess if I ever found a scrap objective I could try carefully cutting it off and replacing it when I'm done but it looks like I'll have to live with the grease for a while. The only other thing I know to try would be to heat it up but that doesn't sound like a tremendously advisable thing to do to a precision optical component

[Hobbyst46]

Well I have tried numerous methods so far, including with the addition of penetrating oil down in the groove, and this thing just absolutely will not budge. I think I'd need an F1 wheel gun to have a hope. Maybe someone disassembled it before me and covered the threads in loctite. I guess if I ever found a scrap objective I could try carefully cutting it off and replacing it when I'm done but it looks like I'll have to live with the grease for a while. The only other thing I know to try would be to heat it up but that doesn't sound like a tremendously advisable thing to do to a precision optical component

The leather straps and vise-grips method involves intense force to rotate.

[PeteM]

Here's another case where heat, precisely and carefully applied, could help. It can free Loctite if that's been applied and open up some space between the threads for penetrating oil if they are stuck and usually if they are somewhat corroded.

I resort to it when other methods fail, and the choice is between an unusable objective worth nothing - and a potentially restored one. If an eBay return is possible and you didn't get a massive bargain, that might be the better alternative.

Apply the heat precisely and evenly to the circumference of the part you want to expand, avoiding exposure to the glass. Various tools to do this have been discussed before.

So far, I've had about a 90% success rate, usually getting seemingly locked-solid things free and sometimes damaging things in the process. A memorable success was freeing up a 60x Leica Plan Apo infinity oil objective that cost a pittance and now works like new. When an interchangeable turret I need shows up with an objective stuck to it with clear signs of attack by a Vise-Grip wrench, it's been a 100% success rate - often with a marred but usable objective gained in the process.

A memorable failure was trying to remove the back element of an Olympus 20x SPlan to swap in a phase annulus from a 20x SPlan phase objective with a bad front element. That took a second attempt

Truly effective equivalents to the strap wrenches noted above make a big difference. In addition to strap wrenches, there are connector pliers (think arc-joint pliers with soft faces), custom-made clamps made by drilling out and sawing wood blocks, camera lens pliers either bought or custom-made -- and best of all -- 5C collets.

[apochronaut]

Well I have tried numerous methods so far, including with the addition of penetrating oil down in the groove, and this thing just absolutely will not budge. I think I'd need an F1 wheel gun to have a hope. Maybe someone disassembled it before me and covered the threads in loctite. I guess if I ever found a scrap objective I could try carefully cutting it off and replacing it when I'm done but it looks like I'll have to live with the grease for a while. The only other thing I know to try would be to heat it up but that doesn't sound like a tremendously advisable thing to do to a precision optical component

That design, with a bottom ring nut is a common one and they can be hard to remove. Usually a bit of penetrating oil does free them up but it might take a day or two and possibly more than one treatment. Bob is correct, the tightness of some components is surprising and the leather belts can also slip on smooth surfaces. You can also tighten the grips too much and pinch a thin ring nut on the threads. You just want the curved vice grip jaws to bite into the leather and compress it against the ring and barrel enough and no more, and be carefull to not accidentally overlap a strap onto both components. A couple of bungee cords are also possibly good. Directed heat, as Pete M has suggested may be a must in this case.
I have a couple of thoughts on the origin of the problem. One, is that it for some reason it might be a left hand thread. I know the one in mineral rob's picture is a right hand thread but it might be worth a try, just to rule that out. It is unlikely to make matters worse, since if a right hand thread, it is so tight anyway.
The second thought is that it is bound on the thread due to a pulled thread and may be ever so slightly cockeyed or just seized on a partially stripped thread. This could have happened in the factory. Brass is soft and fine brass threads can pull more easily than those of anything else except of course copper and aluminum. If the thread is pulled, that could be the reason or one of the reasons it is sticky. It may have had problems from the getgo and some users put lubricant up there, which may have solved the problem temporararily but eventually the gummy bears got it.
I had one like that once , could not get the collar nut off and the only way I could get the optical section free was to lightly buff the tight side of the lower, optical barrel with very fine emery paper. Luckily , the sticking part was closer to the tip. If you have gumming up inside as well and cannot get the nut off, that is not a correction collar objective, so there should be no opening between the outside of the optical barrel and the inside, except perhaps a threaded hole for a locating/travel pin. That should be well plugged. I can see the potential value of freeing up that gumming with a small amount of solvent.
..... all dependant on whether that ring comes free but if it does not, that is a possible contingency.