Jump to content

Case-back threads


Klassiker

Recommended Posts

I have disassembled, lubricated and reassembled a number of movements and complete watches now, beginning with pocket watches and moving on to wristwatches. I have also attended some of the seminars offered by the DGC here in Germany. I would still classify myself very much as a beginner.

One of the first wristwatches I began work on was my Grandad's old Summit with an AS 1700 movement. The filled gold case was worn and filthy, and the lugs were so damaged it was unwearable, so there was nothing to lose at that stage. However, I took the decision to invest some time and money into it, with the aim of making it wearable again. If I can get it finished to a reasonable standard I thing my Dad would like to have it. I have had the case repaired and refinished, and I have serviced the movement myself. I also cleaned the dial and re-lumed the hands, put a new crystal in and replaced the gaskets.

Here are some before and after photos ( by the way, it's Dropbox. From past experience, when you follow the link, the pic is briefly displayed, then disappears. Click the button at the bottom (Oder weiter zur Webseite) to get it back). Thanks for looking! :

A dirty face:

https://www.dropbox.com/s/ujhlz1ihfv4urv2/DSC00865.JPG?dl=0

A clean face. So clean in fact, that the printing came off in the wash. Note to self: never put dials in the ultrasonic bath.

https://www.dropbox.com/s/0q6ez1ick340y9r/DSC01367.JPG?dl=0

Damaged lugs, worn plating and a very dirty movement:

https://www.dropbox.com/s/e7ijw5a0csfqpr4/DSC00877.JPG?dl=0

https://www.dropbox.com/s/d3mt0mhxf3q8bhi/DSC00879.JPG?dl=0

After refurbishing and service:

https://www.dropbox.com/s/2y8k2rbg0usbnb0/DSC01368.JPG?dl=0

https://www.dropbox.com/s/0nrbw3onyk7blz4/DSC01369.JPG?dl=0

Maybe I should write a longer post with more photos of that process elsewhere. Progress is now stalled completely as I have a problem which, despite many searches here and on other forums, I can't find a solution for. At some stage the thread on the case-back and in the watch case itself have become so worn or damaged that they don't lock anymore. In fact, they are so loose now I can snap the back on and off.

Here's a picture of the thread in the case:

https://www.dropbox.com/s/dqe0ikoaokxazq4/DSC01362.JPG?dl=0

And here's the case-back:

https://www.dropbox.com/s/949md0uwn8qindn/DSC01363.JPG?dl=0

I would appreciate any advice about what to do, and especially what not to do at this stage. It's hard to tell from these pictures, but I'm fairly sure the thread in the case itself is beyond repair. It may be possible to redress the one on the back. For sentimental reasons I'd like to preserve as much of the case and back as possible. The case-back for example has the family surname and some dates scratched in there, from the local watchmaker.

I've considered just glueing everything together and hoping it comes apart again when I do the next service, or trying to regenerate a serviceable thread with two-component adhesive. Other than that, I suppose I'll have to wait until I get my first lathe!

I'm  open to any other ideas or tips you can offer. Also, if I've missed a thread showing what to do, please let me know.

 

Link to comment
Share on other sites

It’s a tricky issue as the case has simply lost material due to corrosion. 

Can you try a little plumbers (PTFE) tape? Remember to wrap clockwise onto the caseback thread. 

Another alterantive could be experimenting with different rubber gaskets to see if any can help to form a reasonable seal. 

Link to comment
Share on other sites

I tried the PTFE tape, and it worked well enough so that the threads engaged and I could screw the back on. I gave it a little tweak with the wrench, but it's only slightly more than finger-tight. It was on the wrist today and didn't work loose, so.....success, I guess. Thanks very much for the suggestion. Certainly for the moment that has saved me a lot of heartache. Maybe beginners luck, or maybe with a few more attempts I can get it to grip harder. I think I'll quit while I'm ahead though (for a while anyway).

However, I fear it is only a matter of time before the threads part company again, with a further loss of profile. Anyone got a suggestion for a more permanent solution?

Link to comment
Share on other sites

This is such an unusual failure that there really isn't much information available. IF you have access to a lathe, the threads can be recut in both the case and on the back plate. It would take a good skill level and an even better eye. Do you have any idea of the thread diameter and pitch? 

Additional wraps of the PTFE tape may make the back more secure for a short term repair. Please keep the forum posted on what you do.

Link to comment
Share on other sites

Hi Don,

yes, so unusual that I haven't been able to find any useful tips anywhere else. Not even in the best books I have. So a big thanks to you and rodabod for giving me the benefit of your experience.

I don't have a lathe, and at the moment I've nowhere to put one. Otherwise I'd be tempted to use this as an excuse to go shopping. I could measure the thread, but for the time being I'll just have to be content with the PTFE tape.

Link to comment
Share on other sites


 

On ‎2‎/‎22‎/‎2019 at 12:29 PM, rodabod said:

The issue is though, you can only cut the case-back thread smaller, and the case thread larger...... 

I would start by measuring what's left of the original threads, and decide if the one on the case back can be used with just a clean-up, to tidy the flanks without removing metal from the crown, or cutting the root deeper. Best to keep it to a standard size if possible. Then I'd cut the thread in the case away completely by boring out to the case back o.d. and make a  ring to fit inside. (Material? Push-fit, glued or soldered in?) Then I'd cut a new thread into the i.d. of the ring. Does that sound like a cunning plan?

Link to comment
Share on other sites



  • Recently Browsing

    • No registered users viewing this page.
  • Topics

  • Posts

    • Thank you so much, Hector and CJ. I appreciate the tech sheet and the video. Gasp, I think I will make the attempt. What's the worst that can happen? I think there may be a new balance complete in my future, though.  I'll update the post and let you know the result. R, Frank  
    • So here is the new base (v 2.1), I made it so that the base will fit over and swallow the stump of the hand pusher tool (or at least my clone of the tool), I also reduced the OD of the bottom skirt a little as it looked/felt a little large, here are a few pictures and the fake .pdf file which you need to convert to .zip once downloaded.   The cut-out seen on the below image on the bottom of the base should swallow the OD (40 mm, +0.1 mm tolerance) of the stump and the height of the stump 9.5mm (measured to 9.1mm, but rounded to 9.5mm) - let me know if this works for your tool.   Note, I think you may need to print supports for the new internal shelf created? Here is the fake .pdf for just the FreeCAD base file and 3mf files Modular Movement Holder.pdf Here is the fake pdf for complete set of the new base and ring FreeCAD/3mf files: Modular Movement Holder base and ring v 2.1.pdf However, I'm wondering how often you could use this feature, adding the dial usually increases the OD of the movement, so you would need a new (larger) adapter ring tuned to the OD of the dial and I wouldn't like to grip the dial in any kind of movement holder if It could be avoided for fear of damaging it. Maybe I'm misunderstanding you?
    • Hi Frank, you have dived headlong into the deep end. Hairspring work has to be the scariest thing a newbie has to tackle. Your hairspring appears to be bent and just putting it back into the regulator would not allow the balance to work properly. It might start oscillating but the performance would not be good. The proper thing to do is to unstud the hairspring, remove the hairspring from the balance, reinstall the hairspring on the stud carrier, reshape the endcurve and centre the collet to the balance jewel hole. This challenge would either make you or break you. Hope that you will be able to fix your watch. Welcome to the world of watchmaking.  Watch this video. It think it'll give you an idea of the task ahead. From your 1st photo, I think you have a etachron type stud. Let me see if I can find a video on how to remove it from the arm.
    • Have read of the Tech Sheet attached on the balance section page 12. It may be bent but until you reposition it back in the regulator pins you'll never know. Cheers CJ 4R35B_4R36A.pdf
    • Aloha All, My Seiko 4R35B movement stopped working today. Upon closer inspection, it looks like the balance spring came out of the regulator pin. This is my first time working on a balance. Any advice on how to get this spring repositioned (back to normal)? I'm pretty sure that while adjusting the beat error on this movement, I must have turned the stud (I didn't even know they turned), and the spring eventually fell out.  Will the spring go back to even spacing when it's back in the pin, or does it look bent? Thanks, Frank  
×
×
  • Create New...