Ratchet Wheel Screw: Always Reversed From Direction Of Turn?

Discussion in 'Watch Repair' started by everydaycats, Nov 30, 2014.

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  1. everydaycats

    everydaycats Registered User

    Aug 11, 2011
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    As a rule-of-thumb will the ratchet wheel screw always be reverse threaded from the direction of wheel turn? Assuming a single screw...
    Thanks
     
  2. cbaron

    cbaron Registered User

    Jan 19, 2012
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  3. richiec

    richiec Registered User
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    Feb 24, 2007
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    I know from my limited experience that Waltham rarely uses a left hand thread on its ratchet wheels but Elgin does.
     
  4. doug sinclair

    doug sinclair Registered User

    Aug 27, 2000
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    Certainly, some watches use a left-handed screw on the ratchet wheel. Most watches with exposed winding wheels use a left-hand thread on the crown wheel screw. Once in a while, a crown wheel screw will have three screw driver slots, OR and extra notch radially cut into the edge of the screw head. These will be left-hand thread. But you may run into such a screw on the ratchet wheel as well. But once in a while, you may run into a watch with the crown wheel and ratchet wheel under the barrel bridge. If and when you do, the ratchet wheel screw is right hand thread 99.9% of the time. If a crown wheel has a core (hub) held in place with two screws, these will be right-hand thread.
     
  5. Jerry Treiman

    Jerry Treiman Registered User
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    Richie - did you mean to say "crown wheel"?
     
  6. richiec

    richiec Registered User
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    Whatever Jerry
     
  7. everydaycats

    everydaycats Registered User

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    #7 everydaycats, Nov 30, 2014
    Last edited: Nov 30, 2014
    Crown wheel...my mistake. cbaron and Doug pretty much covered the bases above by describing the ratchet wheel and crown wheel...
     
  8. Skutt50

    Skutt50 Registered User

    Mar 14, 2008
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    There seems to be a very simple explanation to why the crown wheel screw is left hand threaded.

    I have come across one or tow watches with a right hand threaded crown wheel screw but this was the result of earlier erroneous repairs. The result was that when winding the watch the crown wheel unscrewed the right hand threaded screw and the winding did not work!
     
  9. doug sinclair

    doug sinclair Registered User

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    Some watches have a right hand thread on the crown wheel! Some 16-size Walthams for example. With these watches, once the crown wheel screw, crown wheel, crown wheel hub (core) are removed, under the crown wheel there is a steel spacer washer which is held in place with a small screw. If you flip the crown wheel hub over, you find a notch which fits over the small screw on the spacer washer. This prevents the crown wheel hub from turning, thereby preventing the crown wheel screw from loosening. There may be other watches with a similar arrangement.
     
  10. RJSoftware

    RJSoftware Registered User

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    Some of the Bulovas are right hand. The cheap mass produced one I think. Caravel, I think... I definitely remember busting one cause I was sure it was suppose to be left hand.

    I know about the 3 slit identification. But I am not sure it always is done. Best test is a small tweak in one direction and then a small tweak in the other. I do left first because that's what it should be.

    Least that is my experience. I hate forgetting.

    RJ
     
  11. everydaycats

    everydaycats Registered User

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    I knew about the three-line marks in industrial applications, but never seen it used in watches...I was at my brothers place of work a few years ago which was a huge industrial plant with huge machines. Two of his workers were trying to loosen a large bolt, but it would not budge. I happen to see three engraved marks next to where the bolt was and I mentioned to my brother that I had heard those marks indicated reverse threads, and once they applied force opposite to what they thought was correct the bolt broke loose. But, that bolt had a head probably close to two inches in diameter. Again, in my very limited experience I've never seen it in a watch.
     
  12. Al J

    Al J Registered User

    Jul 21, 2009
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    Crown wheel screws are left handed, except when they aren't. Left hand threaded screws have 3 slots in them, except when they don't. That pretty much sums it up. :)

    Cheers, Al
     
  13. everydaycats

    everydaycats Registered User

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    :cool::thumb::clap:
     
  14. watchwldr940

    watchwldr940 Registered User
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    To add a bit-- the Font 60 (I believe) has a left handed ratchet wheel screw. Why, I don't know, but over the years I've accumulated a bunch of these movements with the screw broken off. When in doubt, apply gentle pressure first in one direction, then the other until it loosens. These movements have no indication that this screw is left handed so they are often broken. George
     
  15. everydaycats

    everydaycats Registered User

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    I ran across this picture today while browsing in the swamp and I noticed the three lines. I assume this is a properly marked reversed threaded screw. This is the first time I have seen this:
    Screen Shot 2015-01-10 at 7.48.49 PM.png
     
  16. Samantha

    Samantha Registered User

    Jun 28, 2009
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    Yes, that is a properly marked reverse threaded screw.
    Samantha
     
  17. Firegriff

    Firegriff Registered User
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    Screws/nuts on counter shafts usually have threads opposite of the driven shaft so wont loosen the screw/nut on the counter shaft.
     

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