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AS 978 screw direction

lexacat

By lexacat
in Fault Finding / Fault Diagnosis

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lexacat WRT Addict

lexacat

Posted
Posted

I managed to shear off the head of the barrel arbor screw in this ridiculously tiny movement. Can someone confirm I'm not going insane, and that these two screws are reverse threaded? There are no markings to 
indicate direction.

I've purchased a donor that I can use the barrel arbor and screw from (and anything else I manage to ping into space), but I really don't want to destroy that when it turns up...

Turning in the direction of these should loosen these screws, correct?
image.png.34614577c7c4de561bedaa431da74446.png

Also, I need smaller screwdrivers, damn.

mikepilk Distinguished Member

mikepilk

Posted
Posted (edited)

The crown wheel screws are always (?) reverse threaded (if it's only one screw in the centre), or they would tend to unscrew as the crown turns.

The Barrel screw is almost always a normal thread, though a few are reverse. You can try them either way if you turn the screwdriver a tiny amount.

I've just finished working on a tiny one too. You get used to it 😀

9.thumb.jpg.7e361f8ba1b31afd43a1ff45e3221fa3.jpg

 

Edited by mikepilk
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lexacat WRT Addict

lexacat

Posted
  • Author
Posted (edited)
1 hour ago, mikepilk said:

The crown wheel screws are always (?) reverse threaded (if it's only one screw in the centre), or they would tend to unscrew as the crown turns.

The Barrel screw is almost always a normal thread, though a few are reverse. You can try them either way if you turn the screwdriver a tiny amount.

I've just finished working on a tiny one too. You get used to it 😀

9.thumb.jpg.7e361f8ba1b31afd43a1ff45e3221fa3.jpg

 

Cheers! Turns out this one must be reversed. I turned it the normal direction and it sheared. 

 

Actually, I'll try and see if there's enough thread remaining on the screw to check. 

Edited by lexacat
mikepilk Distinguished Member

mikepilk

Posted
Posted

They are rare, but I've had a few with reversed ratchet screw - mainly AS from what I remember.

Just had a look through some of my watches and found this for and AS 984. I made a note at the time, to avoid a problem in future.

Barrel-0004.thumb.jpg.0b8b0460ff61364af4be7fb3b8fdd45a.jpg

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lexacat WRT Addict

lexacat

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Posted

thanks @mikepilk !

They are both definitely reverse threaded 😃 Mistakes were made 🙄

Once the donor gets here I'll just swap out the arbor and screw, but what a pain! Also waiting on a tiny movement holder, this thing is so tiny!

As an aside, there's no way I'm servicing the mainspring. I don't have a winder small enough.

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