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Balance Pivot Length Measurment

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bobolink Watch Enthusiast

bobolink

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Posted

Ive been working on an Omega Pocket Watch that started with a mainspring replacement and cleaning that went fine.  My one problem is getting the escapement back together.  I could never tell if it actually was working right before disassembly.  It spun freely with air.  But now trying to reassemble it the balance will not sit in the jewels correctly.  The pivot looks fine, no bends, brakes, etc.  Its just as if the pivot isnt long enough.  I didnt replace any of the escapement parts or take it apart.  I know someone had worked on the watch before I got it (the barrel gear was put on incorrectly).  So I am wondering if the pivot was changed and an incorrect one was installed.

My question is how do you measure the required length of a balance pivot?  lets assume you do not have an existing one to work with.   Is there a special tool for this ?


Thanks

Bob 

WatchMaker Super WRT Addict

WatchMaker

Posted
Posted

Do you know the calibre of your movement?

If it's in this list then the dimensions of each staff are given:  https://www.balancestaffs.com/omega.php 

Bestfit also includes staff references for calibres. In fact for Omega there are separate pages devoted to it (pp589-591 in the version I have). If you come back with that calibre number I'll try and help further.

As a ready reckoner though you could fit the balance bridge - minus balance - and then use a straight strand of copper wire (robbed from a bit of multi-strand electrical cable). Block the bottom jewel hole with a bit of Rodico pushed into the hole slightly to emulate where a pivot extremity would be. Gently thread the wire through the balance bridge jewel hole until you find resistance from the Rodico. Now mark the other end of the wire for where you think the top pivot extremity would be. Measuring the resultant length of wire with digital calipers should at least get you in the ball park of whether your current pivot is rogue or not.

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