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How common is this


Paul80
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Hi all

When I first started on my journey into watch repairs I made two promises to myself, one was to never work on a Ladies size watch and the other was to never work on a Chronograph.

Unfortunatly I have become a little bored with no normal sized watches to work on and a bag of Ladies watches given to me at the start of my watch repair journey by a friend of my sons.

So desided to see how many of the Ladies watches I could loose parts for. 😎

I actually surprised myself with how many I got stripped cleaned and back together and they even worked, a few ended in the for parts box bcause of either parts lost to the ether or parts found broken, but about 50% are back in working condition, which I must admit was a huge confidence boost as I was sure they were just too small for me to ever think about working on one.

Now the point of this post I came across something I had not seen before with the standard size watches.  Below is a picture of two of them, one out of a Swiss Rotery and the othe out of a German watch , can you see the issue.

The righthand one, the Rotery has the screws for the Ratchet & Crown wheel marked with 3 lines indicating they are both left hand thread and on the German watch both the screws have no extra marks indicating they are both righthand thread.

Howver in both cases all 4 screws were lefthand threads, never seen a lefthand thread screw on the ratchet wheel before (I have only worked on Japanies watches uptil now).  Is this a common practise with European made watches or something unusual..

Thanks for any insite into this.

Paul

2022-05-19 14-09-14 (C,Smoothing4).jpg

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1 hour ago, Paul80 said:

can you see the issue

I think relying on the "stripes" on the screw head is the issue.

If they're there, great but don't think that a normal screw head can't be left-handed and don't assume that the ratchet wheel can't have a left-handed screw either.

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I would say that most of the Swiss movements that I have worked on over the years have had right hand threaded ratchet wheel screws. However maybe 10% have been left handers.

As for the 3 slot marking to indicate reverse threads although I have encountered it on Swiss movements I find it's more of a non-Swiss practice, more common on Russian and Japanese movements.

The thing with left hand threads is that they are inteded to prevent the screw from being undone in the event that the component that they are screwed into has a normally anti-clockwise direction of rotation, which would loosen a right handed thread unless there was some other means of preventing the component turning independently of the screw. With the ratchet wheel the screw goes into the mainspring arbor which is locked to the ratchet wheel via the square. Because the square locks everything together the screw can be left or right handed without issue.

 

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I have come across left-handed threads on ratchet wheels several times - without it being indicated with 3 stripes.

It has been mentioned before - it was suggested that it was done to save one extra tooling operation (changing to a LH thread tap)

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The problem is while its ok to assume the crown wheel screw is going to be a left hander regardless of the screw head being marked, with the ratchet screw its easy to assume its a righthand theaded screw only to break the head off thinking its just tight.

Like I said, just wondering how common it is to find a lefthand threaded screw in the ratchet wheel so I know if I need to look out for it with certain makes of movement.

Or is it just pot luck and a tight screw might be just tight or a left hand thread ?, is it just coincidence I have encountered two in the last couple of days.

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58 minutes ago, Paul80 said:

Or is it just pot luck and a tight screw might be just tight or a left hand thread ?, is it just coincidence I have encountered two in the last couple of days.

It's not common, @Marcreckons about 10%, a bit less in my experience. I've learnt the hard way to go easy with ratchet screws. If it's tight to undo, I try it the other way

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Citizen uses left-hand screws on the ratchet wheel of their older hand-wind movements (0200  series). Perhaps to prevent watchmakers to power up the mainspring by winding the barrel with the ratchet screw (as it will just unscrew)? There is no other reason as the ratchet wheel sits on the barrel arbor square end. On some models they have three stripes but on other no. I'm quite fond of these movements so I have done a lot of the, but it can catch you out.

Anilv

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