Question about screw-down crowns

Thread: Question about screw-down crowns

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  1. #1
    Member Hotspur000's Avatar
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    Question Question about screw-down crowns

    I have a Mido Ocean Star with a screw-down crown, which is my 'evenings and weekends' watch, meaning that for the majority of the work week it's sitting at home on a table. Normally in the mornings I give it a good twirl to get it wound enough to last the day so it's still going when I get home, but I slept in this morning and so didn't have time, and when I got home today I saw that it had stopped just after noon.

    Now, I know this normally isn't a big deal -- you just move it around a bit to get it going again -- but this watch has a screw-down crown, and, from what I understand, cork inside to keep water out. My question is -- given that cork could presumably wear down pretty quickly if it had a screw constantly being screwed in and out, is it inadvisable to have the watch stop and have to open the crown frequently?

    Is it any different than with another automatic that doesn't have a screw-down crown?

  2. #2
    Member Oldheritage's Avatar
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    Re: Question about screw-down crowns

    My experience with Mido screw down crowns using cork has been very positive. Don't worry about it, set the watch as needed.
    Lover of watches from all around the globe.

  3. #3
    Member lysanderxiii's Avatar
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    Re: Question about screw-down crowns

    Cork?

    Just how old is that watch?
    familiaritas parit contemptum; raritate admiratione wins.- Lucius Apuleius
    est necessry, accurate ad secundo? - Lysander magna
    iustum est horologium - Obscurus Genius

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  5. #4
    Member Hotspur000's Avatar
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    Re: Question about screw-down crowns

    Quote Originally Posted by Oldheritage View Post
    My experience with Mido screw down crowns using cork has been very positive. Don't worry about it, set the watch as needed.
    Very good to know.


    Quote Originally Posted by lysanderxiii View Post
    Cork?

    Just how old is that watch?

    Brand new. I actually just did a search and found this info in another thread:

    Quote Originally Posted by obsidian View Post
    Mido's old naming conventions have very specific meanings:

    Ocean Star: indicate that the watch has the Aquadura crown sealing system which maintains up to 50M water resistance even if the crown is pulled out-- something no other company can claim.

    From Mido's website:
    "In 1934, Mido invented the unique Aquadura cork crown sealing system. It ensures complete water-resistance with a specially treated piece of natural cork, which is nestled around the crown shaft. A secret treatment keeps the cork moist and thus preserves its elasticity for years. Even if the crown is not fully pushed in, it is still water-resistant. Aquadura is designed for frequent contact with water up to 50 meters (5 bar) but not for deep water diving."

    Commander : indicates the watch has a one piece case for added water resistance security-- the movement is accessed from the front of the case. You may see some older models that say both Ocean Star and Commander on the dials.

    Multifort :
    From Mido:
    1934: Launch of the "Mido Multifort", which was absolutely watertight, antimagnetic
    and impact resistant. One of the most important milestones in the brand
    name's history. The introduction of this watch provided the Mido brand with
    a totally new image which right up to the present day has served as a
    basis for the development of watches: clear, original design, very resistant
    and functional usage.To prove that the watch functioned perfectly under
    very extreme conditions, Mido had this model tested very thoroughly by
    the New York "Electrical Testing Laboratories Inc.". Underwater tests were
    conducted in freshwater and saltwater for over a thousand hours. The watches had to
    withstand ten cycles of 15 minutes of 50°C heat followed by –40°C cold. The
    winding crown had to pass a test representing 34 years of use. Immersion tests to 13atm (120 m.) as well as altitude tests to 6600, 13 300 and 16 600 metres were
    simulated and Mido unfortunately had to record the only failures of the entire test
    procedure. One of the 6 watches tested ceased operating at 13 300 metres. This
    procedure was the official test of the American government.
    The trailblazing new sealing system, assuring almost complete watertightness
    was the key to these superb results. It involved the use of specially treated
    natural cork which sealed the crown insert, the critical point of all wristwatches.
    Because it formed such a perfect join with the winding shaft, Mido was able to
    guarantee absolute watertightness even when the crown is pulled out. Between
    1934 and the present day, this unique system has proven itself excellently and
    protected valuable mechanisms from water. In 1959, this cork system was
    named "Aquadura".

  6. #5
    Member Oldheritage's Avatar
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    Re: Question about screw-down crowns

    Well, that said, I thought there were only some vintage watches using the aquadura system in combination with a screw down crown. According to their own website, only the "Commander" range still uses the aquadura system with cork. The Ocean Star range uses normal gaskets.
    Lover of watches from all around the globe.

  7. #6
    Member lysanderxiii's Avatar
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    Re: Question about screw-down crowns

    And, while no other company does claim water resistance with the crown unscrewed, most actualy could if they felt like testing and claiming....

    Most screw down crowns look like either Figure 1 or Figure 2. As you can see there are two gaskets, one always on contact with the case tube, and one securing the crown when screwed down.

    Figure 1. Standard Screw Down Crown with External Threads.


    Figure 2. Standard Screw Down Crown with Internal Threads.
    familiaritas parit contemptum; raritate admiratione wins.- Lucius Apuleius
    est necessry, accurate ad secundo? - Lysander magna
    iustum est horologium - Obscurus Genius

  8. #7
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    Re: Question about screw-down crowns

    Somebody still uses cork? Strange they did not change to a better material. Even many Wine producers are using polymers these days. Polymers that let in certain amount of air, just like cork does.

    On your watch, I would have my watch maker test the WR rating at least twice a year.

  9. #8
    Member Oldheritage's Avatar
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    Re: Question about screw-down crowns

    Honestly, the treated cork that my Mido Multifort uses still seals fine after more than 60 years.

    The OP's watch doesn't use cork, the modern line of Ocean Star watches use normal gaskets.
    Lover of watches from all around the globe.

  10. #9
    Member Hotspur000's Avatar
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    Re: Question about screw-down crowns

    Quote Originally Posted by Oldheritage View Post
    Honestly, the treated cork that my Mido Multifort uses still seals fine after more than 60 years.

    The OP's watch doesn't use cork, the modern line of Ocean Star watches use normal gaskets.
    Ah, quite right, quite right. I see it now.

    Then really nothing to worry about. Excellent.

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