Need help with a stuck part on a Zeiss PM3 tube head

[tlansing]

The clamping screw on the tube head (see arrow in photo below) is stuck and as a result I can't attach the binocular head to the tube head. I have loosened the clamping screw and tried to push, with the flat face of a screw driver, on the part that extends into the opening where the binocular head attaches to see if I could get it to move but without success. I have also tried loosening the two other smaller screws (seen in the photo at about 8 and 10 o'clock) but that hasn't worked either. I would appreciate suggestions about how to get the clamping screw loosened and thanks in advance for your help.

Tube head.jpg (72.1 KiB) Viewed 10127 times

[Hobbyst46]

Did you try a drop of light machine oil on the stuck pin ? penetrating oil maybe ? that part is over-engineered IMHO.

[Scarodactyl]

These pins are awful, just below whatever lens cement they used on my 'things I don't like about Zeiss' tier list. The outer thumbscrew depresses the spring loaded inner pin, so make sure it's actually stuck and not just zeiss's dumb design acting differently than the set screws every other maker used.

[imkap]

I think you should be able to remove the whole spring screw assembly by unscrewing the set screw. Just carefully and with a right screwdriver as Zeiss set screws are easy to break. Then soak in gasoline, ethanol or whatever, disassemble, regrease and assemble...

You did unscrew the cap completely? I see it's screwed on in the image. Seems obvious but...

[tlansing]

Hobbyst46, Scarodactyl and imkap: Thanks for your comments and advice. I have some additional comments/questions.

@Hobbyst46: I applied small drops from a syringe of WD-40 to the end of the clamping screw that is covered by the cap. I applied a drop, let it dry and then applied another drop. I was pretty paranoid doing this, as I have read so much about avoiding using WD-40, but I used such small amounts (and no spraying!) that I thought that was OK. I then tried to push in the end with the flat end of a screwdriver, but so far no success. Any other ideas of a solvent to use?

@Sarcodactyl: I did not understand your comment, "The outer thumbscrew depresses the spring loaded inner pin, so make sure it's actually stuck and not just zeiss's dumb design." How do I determine if is actually stuck or the result or a dumb design?

@imkap: I was curious about your comment,"I think you should be able to remove the whole spring screw assembly by unscrewing the set screw." I have looked over the clamping screw and I don't know where the set screw is. Could you clarify this with a picture? Thanks!

[imkap]

There is a set screw in a small hole just near the spring at 3 o clock. I think it holds the thing in place, so unscrew, soften with ethanol and try to remove. Just careful not to damage the set screw

[Scarodactyl]

In any other maker's scope you would just unscrew the entire pin which is a single piece, so it is easy to think a Zeiss pin is stuck when adjusting that outer screw does nothing visible (it only adjusts the springiness of the pin) I believe these are meant to be used by depressing that spring loaded pin with the edge of the dovetail, inserting it fully and then allowing the spring action to press the dovetail against the fixed set screws. So before concluding it is stuck just be sure that pin won't depress at all.

[imkap]

Tube head.jpg (76.29 KiB) Viewed 10060 times

[imkap]

And first unscrew the cap and see what is happening as Scarodactyl says.

[tlansing]

imkap, thanks very much for your help with this problem. I had removed the cap of the clamping screw as shown in the photos below. In the first picture, the red arrow shows the set screw that you mentioned. I have a watchmakers screwdriver and can loosen this screw. Both pictures show the pin protruding from the interior of the clamping screw. The arrow in picture 2 shows where I have been trying to apply WD-40 to the pin to loosen it, but so far no success. In one of your posts referencing the set screw you said, "I think it holds the thing in place, so unscrew, soften with ethanol and try to remove." By this did you mean remove the set screw and put some ethanol in the set screw hole to try to loosen it? How would the entire clamp screw assembly be removed? I appreciate very much your help!

Tube head2.jpg (118.48 KiB) Viewed 9981 times

[imkap]

If you unscrew the set screw I think the assembly should come out. If it doesn't then apply ethanol and try again. Just pull it out. Be careful with 100% ethanol as it might damage the paint.

I remember removing the assembly on my GFL, but don't have it here so cannot check. But can't think of any other use for the small set screw.

After removing the assembly you can soak it in some solvent and it should loosen.

[Charles]

If memory serves me right, the the unit needs to be unscrewed out and not pulled out. The set screw keeps it from turning. I put tape around the exposed threads if it needs more force than just the fingers and unscrew the unit. Then soak in a solvent or WD-40 and work the plunger back and forth. Then grease with a light grease or oil.

[ImperatorRex]

These pins need to be completely dismantled. Use petrolether or xylene to remove the old, hardened grease. Relubricate and re-assembly.

Here you find the details of the pin mechanism. The principle is all the same on the Zeiss standards (PM):

https://www.mikroskopie-forum.de/index. ... 6#msg25486

[imkap]

If memory serves me right, the the unit needs to be unscrewed out and not pulled out. The set screw keeps it from turning. I put tape around the exposed threads if it needs more force than just the fingers and unscrew the unit. Then soak in a solvent or WD-40 and work the plunger back and forth. Then grease with a light grease or oil.

This is most probably true, I remember other parts with the pin being like that...

[tlansing]

Thanks to everyone for their comments/suggestions. I also posed this question on the German Mikro-Forum (I am a big fan of this forum thanks to Google translate which allows me to read German), and here is a link to the recommendations I got from that forum. There were, of course, some similarities and some cautions that I thought were helpful. Still working to get the #%&#! thing unstuck!

https://www.mikroskopie-forum.de/index. ... ic=46654.0

[Charles]

Probably the easiest way is once you unscrewed the knurled part, pull off the C clamp holding the spring and plunger, then you can just pull the spring off one end and the plunger out the other end, clean everything and then reassemble.

[ImperatorRex]

Hello Tlansing,
thrust me, from my own experience do not try to remove the threaded brass sleeve...it is not required and has NO benefit.
Just remove the small retaining ring from the "shaft / pin", should work with a tweezer. Then you can remove all the interns (spring, shaft-pin) as shown on the photos that I shared before.

[imkap]

Hello Tlansing,
thrust me, from my own experience do not try to remove the threaded brass sleeve...it is not required and has NO benefit.
Just remove the small retaining ring from the "shaft / pin", should work with a tweezer. Then you can remove all the interns (spring, shaft-pin) as shown on the photos that I shared before.

I agree with this, should be simpler. Just take care not to scratch/damage the glass while doing it, maybe put something over it...

[tlansing]

Hi Jochen,

That makes perfect sense, especially looking at the pictures in the link that you sent. I also was able to visualize the parts in a working one of these clamping screws.

Now the next question: when all the parts are freed and cleaned, what is used to regrease them?

Again, thanks to all for your useful comments!
Tim

[ImperatorRex]

Hi Tim,
I have used the Zeiss GF 30 gear grease. But a soft to medium viscous gear gease should generally do the job I guess.
In the German Forum there is also a member who sells a comparable grease for quite low costs...but maybe would not work due to shipping costs to USA in your case.

[Scarodactyl]

This is heresy, but I have once replaced it with a normal set screw like it should have had in the first place. It was annoying to do though given the unusual fine thread on the outer collar, I basically had to make my own set screw fro threaded rod and a cap.

[ImperatorRex]

Hi Scarodactyl,

This is heresy, but I have once replaced it with a normal set screw like it should have had in the first place.

Wonder why you replaced the wonderfull, over engineered, spring loaded fixation mechanism?
After re-lubricating it will do again a nice job for the next coming 20 years...

Actually I am still fascinated that manufacturing costs did obivously not play a signifficant role in that older area, maybe till the 80's?
On the other side I can see that simple set screws can do the job quite well...but where is the charisma

[tlansing]

Hi Jochen (and others),

I found the link to information on the German Mikro-Forum about the clamping screw to be very helpful. As a follow up, I have been able to remove the cotter pin from the movable shaft inside the outer sleeve after applying acetone to the cotter pin. I also applied acetone repeatedly to both ends of the clamping screw sleeve and then removed the shaft and spring. I then soaked all of these in acetone overnight; the result is in the picture on the left. However, when the movable shaft was inserted into the outer brass sleeve the shaft would not extend much beyond the outer edge of the sleeve, as shown in the photo on the right. I thought there might be some undissolved, hardened grease inside the sleeve, so I wound some steel wool around the end of a small wooden stick to clean out the inside of the sleeve. I blew any junk from inside the sleeve (away from the optical parts) with a blower. Visual inspection seemed to indicate that the sleeve was very clean inside but the movable shaft still would not extend much more than it had before. I thought maybe the set screw, shown at the arrow in the middle photo, was deforming the sleeve inward, preventing the movable shaft from extending further in the sleeve. I loosened it but it didn't help. It seems like the fat end of the movable shaft was getting stuck somewhere inside the sleeve, but I am at a loss to know what to do next. Suggestions would be greatly appreciated!

Thanks,
Tim

Cleaned_Clamping_Screw.jpg (64.62 KiB) Viewed 9395 times

[tlansing]

After much frustration, I finally think I figured out what the problem is with this clamping screw. I had another Zeiss part with the same type of clamping screw and I tested the cleaned shaft/pin and spring in the sleeve from this clamping screw. I worked perfectly! I then tested this same shaft/pin-spring combination in the removed sleeve and it got stuck, indicating that the sleeve must be slightly bent, thus preventing the shaft/pin from sticking all the way through the end of the sleeve where the knurled knob screws on. Fortunately, I have another sleeve of the same length from a salvage Zeiss part that I can use to replace it.

[ImperatorRex]

Congrat's Tim.

Fortunately, I have another sleeve of the same length from a salvage Zeiss part that I can use to replace it.

Press my thumb and good luck!

[tlansing]

I have learned a lot about clamping screws in this thread but I wanted to add just one more follow up that might be useful to others who have experienced this problem. Not meaning to contradict in any way the always useful advice given by Jochen (ImperatorRex) in an earlier post (#17) in this thread, I did find it was pretty easy to remove the brass sleeve containing the shaft/pin and spring, and this made it much easier to clean. I just loosened the set screw (see the red arrow in the picture in post #10) and then was able to unscrew the sleeve with my fingers. In another case, I had removed the cotter pin and then pulled the shaft/pin + screw from the sleeve, loosened the set screw, and turned the sleeve using a small needle nosed pliers inserted into the sleeve. I did not apply much pressure for fear of damaging the thread on the sleeve, as warned about in earlier posts, but all of the sleeves that I have cleaned have unscrewed without really any effort (I should note that I would NOT have proceeded in trying to unscrew the sleeve if much pressure was needed). For me, removing the sleeve and cleaning it away from the optics in the tube head relieved my fear of getting junk on the optical surfaces or scratching them. Once everything was cleaned, regreased and reassembled (sleeve + shaft/pin + spring + cotter pin), I screwed the sleeve back into the tube head until the fat end of the shaft/pin protruded sufficiently into the inside of the tube head to secure the associated equipment (in this case, the binocular head). I then tightened the set screw to keep the sleeve from turning when the clamping screw was turned.

[ImperatorRex]

Hi Tim,
glad that it worked so well! I also learned a lot from your experience, thanks for sharing.