Oops! Barrel arbor screw sheared off.

[buzz12]

Maybe should have asked this question a bit earlierIs this screw ever a left handed thread?

Was happily tearing down my AS 984, until I got to this little swine!  I did get it out but it appears to have sheared off!

Is drilling it out an option, or will I have to replace the arbor?

Any other suggestions as to how I can repair my muck up?

 

 

[ramrod]

i've only known the crown wheel to be reverse threaded. i have never seen the barrel as such. perhaps it was on it's way out already? i'm not sure if there is an easy out that is that small.

plan "b" is to start looking for a naff movement and cannibalize it.

[rogart63]

Have a few of those. Send me a PM .

[buzz12]

Oh well... thought as much! I have no idea why it was so tight.  Maybe the thread was

jiggered and had been put in with thread-lock. One step forwards and two steps back. 

Just when I thought I was getting the hang of things...

[Cad101]

These things are sent to try us buzz. I'm positive you will encounter many more stuck screws on your journey of watch repair.

Mick

[fjseal]

Buzz12,

I recently serviced an AS984, and the barrel screw is a left-handed thread as well as the crown wheel. Luckily, when I tried undoing it and it wouldn't budge, I just tried the other way and out it came. Fortunately, the screw was not too tight. A replacement arbor would seem to be the best solution, and you will need the correct screw with it. Nice little movement, good luck.

Frank.

Edited April 21, 2016 by fjseal
Add more info.

[buzz12]

Cheers Frank, that's a first! Never known a barrel screw be left-handed... thanks for sharing. Just learning all the time.

[ricardopalamino]

6 hours ago, rogart63 said:

Have a few of those. Send me a PM .

I would take up Rogart63 on his offer . after that I would alternately soak the part in vinegar , followed by an ultra sonic treatment then repeat with the vinegar .

[jdm]

5 hours ago, buzz12 said:

Cheers Frank, that's a first! Never known a barrel screw be left-handed... thanks for sharing. Just learning all the time.

Maybe in this case the crown wheel is right handed and turn the other way around?

[buzz12]

Nope jdm, the crown wheel was left- handed as I was expecting. I did try the barrel both ways but not because I thought it would be left-handed but thought it might ease it.  Anyway, Rogart63 has got me sorted so given time it will live again.

[jdm]

9 minutes ago, buzz12 said:

Nope jdm, the crown wheel was left- handed as I was expecting. I did try the barrel both ways but not because I thought it would be left-handed but thought it might ease it.

Cool. But in the industry there is always a reason why certain things are done a given way, and post-fact is fun to make guesses. Perhaps it has been made so for commonalty with the crown screw?    

[Marc]

Fjseal is spot on, I have just checked 2 in my collection, a 7 jeweller and a 15 jeweller, and in both cases both the crown wheel screw and the ratchet wheel screw is a lefty. Unusual, but not unheard of.

Crown wheel screws are usually (but not always) left handed as in most cases the screw is threaded into the barrel bridge and so shouldn't turn, and the crown wheel turns anti-clockwise when the watch is wound. There is therefore a risk that torque could be transferred from the crown wheel to the screw in which case a right handed screw would start to undo. By using a lefty any torque that may transfer from the wheel to the screw would just tighten the screw. In an ideal world though there should be sufficient clearance between the screw and the wheel for the wheel to turn freely when the screw is tight.

The ratchet wheel screw on the other hand is screwed into the barrel arbor and so rotates with the wheel. There is therefore no risk of torque transferring from wheel to screw which means that either left or right handed threads are fine.

As Jdm suggested, this could just be  so that only one type of screw is needed for both functions, and not two, thus economising on manufacturing costs.