Lavina 105 (?) Ratchet wheel screw. Left hand?

Discussion in 'Watch Repair' started by Roy Horrorlogic, May 25, 2020.

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  1. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    I've been caught out a few times by barrel arbour threads in perverse left-hand format. Why on earth this was ever decided on simply beats me. But that doesn't take much. So I'm pretty careful if there's excessive resistance in the right direction. This time, despite my best efforts, I got caught. Unable to free the screw even with the aid of penetrating fluid and a large screwdriver, I put the whole bridge and barrel in an ultrasonic. I should have put some heat on it but I didn't and the screw sheared. I have never yet managed to extract a sheared screw from a barrel arbour. However I have another example of this movement. That screw won't budge either.
    It would help knowing whether this is one of the left-handers. Anyone familiar with the movement? - which may or may not be a cal 105.
    Roy

    View attachment 591797

    20200525_163209.jpg View attachment 591801 View attachment 591802
     
  2. Chris Radek

    Chris Radek Registered User
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    If you look at the remains of your broken screw under the microscope you can usually tell which way the thread goes. Either the partial thread left attached to the head, or the part still in the arbor.

    If you do find it's left-hand, that's good, because if you drill it with a regular drill it'll probably catch and come right out.

    I did find this picture of the 105:

    upload_2020-5-25_10-54-31.png
     
  3. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    Thanks Chris
    there's almost nothing left but the head. But that pic confirms that this is not a cal 105. I believe that Lavina used Favre Leuba movements quite a bit but so far I haven't been able to locate an identical movement. One of these has "705" on the main plate but that's no more help. I'll add a snap of the dial side (minus some parts) in case anyone recognises it. Just tried some heat without success - but I'm being very cautious.

    20200525_163319 (1).jpg
     
  4. Chris Radek

    Chris Radek Registered User
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    Can you show all the keyless parts? Maybe I can ID it. Most of your attachments in the first post don't show up for me.
     
  5. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    OK... I have just discovered that I have a 17 J version of this movement - and the offending screw is a left hander and was quite free. Now nobody could possibly make two near identical movements and....
    Could they? I'll find out shortly.
    Phew, it had a long soak and freed up.
    I wonder where the bonkers notion of having a left hand thread on a component that rotates anti-clockwise came from? I must have seen almost half a dozen different movements afflicted with this trap.
     
  6. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    Here are the two sets of KWs. Oddly they are not the same but the 17J version does match the illustration you uploaded Chris.
    Uploads to the site seem to be very, very slow.
    OK, The KWs are the same but the 15J has a broken set-bridge spring.

    lav-15j-kw.jpg Lav-17J-kw.jpg
     
  7. Chris Radek

    Chris Radek Registered User
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    I think they are Lavina 123. The one on the left just has part of the set bridge broken off.

    upload_2020-5-25_11-36-19.png
     
  8. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    Thanks Chris - I must have amended my post before you replied.
    Does that source specify the main spring data?
     
  9. Tom Huber

    Tom Huber Registered User
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    I've been working on watches for over 40 years. I have never seen a reverse thread on the ratchet wheel screw (barrel arbor screw). If there is going to be a reverse thread screw, it is on the crown wheel.

    Tom.
     
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  10. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    You're implying that I'm mistaken, right? Well, it is an internet forum.
    I'm looking at three of them right now - and I've seen numerous examples on other movements. Unless I've misremembered, in a few cases Dr. Ranfft's site actually mentions this anomaly. At a guess I've personally handled at least six different examples in the last 4 years. This has made me quite cautious which is why I am always very careful with ratchet wheel that appear to be too tight and made me cautious with this Lavina. To no avail.
    Every crown wheel I can recall has a left hand thread. Even the old trucks I was familiar with had studs that tighten in the direction of the wheel's rotation.
     
  11. Chris Radek

    Chris Radek Registered User
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    #11 Chris Radek, May 25, 2020
    Last edited: May 25, 2020
    Sorry no, it's identification only. (AWCI library)

    Tom, I have seen left-handed screws on barrel arbors too, often on little tiny swiss ladies' movements, and it seems like they're never marked with the triple slot, which would really help. It's very annoying!
     
  12. Chris Radek

    Chris Radek Registered User
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    Oh, it's in Bestfit, 6x10x10.5, white-a-loy 610H, samson 6061.
     
  13. Skutt50

    Skutt50 Registered User

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    I also have come across a number of these left hand screws on barrel arbors.

    If I am uncertain I use a well fitting screwdriver and apply a small force both left and right. If no action I continue over and over again with slightly more force until it comes free. I can't remember ever having had one of these screws break....... (Touch wood!)
     
  14. roughbarked

    roughbarked Registered User

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    Yes generally speaking those left hand threads should have a triple slotted head but this wasn't always the case. The little ladies movement mentioned above was the AS 1012 and all its versions from the base model. In general AS often used left hand threaded ratchet wheel screws and yes all crown wheel screws were left hand threads but not always marked as such.
    Lavina 123 = (Angelus 123)
    Remarks
    Angelus 123 und Lavina 123 are identical. Flume catalogs mention the Angelus 123 already in 1952, the Lavina 123 not before 1962. Thus Angelus is likely the maker.

    from Ranfft.

    Yes it is true that experience and memory are required when disassembling all such watches.
     
  15. Tom Huber

    Tom Huber Registered User
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    I said that I have never seen one. but I have never worked on a small Swiss made movement. I work predominantly on American watches. Therefore I have never seen one.

    And to Roy, nowhere did I say or imply that you were wrong or mistaken. I stated that I had never seen one

    Tom.
     

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