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Balance wheel truing

bsoderling

By bsoderling
in Watch Repairs Help & Advice

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bsoderling WRT Addict

bsoderling

Posted
Posted

Hi guys,

 

Working on an old Pierce movement that initially needed a new balance staff. Got that sorted just to find that the wheel has a severe wobble. As far as I can judge it’s not my riveting that’s faulty but more likely the arms that were a bit skewed.

 

Have been thinking to get a truing caliper (or whatever the tool is called) and just laid hands on one of the dual versions.

 

As far as I can judge one of the sides has tiny holes that seems suited for the staff pivots and the other side allows a deeper setting that holds the staff on the ”shoulders”, minimizing the risk to break the pivots while truing.

 

There’s also a small ”handle” that I assume can be used for bending and twisting.

 

If there’s any know how with these operations I’d really appreciate some feedback on what to do and what to avoid.

 

What I’m primarily worried about is the risk of breaking the riveting when applying the needed force to the wheel and arms. As far as I can understand the rivet has to withstand all the force applied.

 

Photos are attached.

 

3fd652156bcad32bd45c9c48f10d79e6.jpgfc08c28df0eac23017378bba6fce3bee.jpg

 

 

 

 

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rodabod Distinguished Member

rodabod

Posted
Posted

I usually bend the individual arms (assuming a split temperature-compensating balance) by holding the opposite arm and twisting. I thinking supporting by the staff is asking for trouble. The tool is for observing true-ness, but I'm not aware of it ever being used for bending the wheel itself.

bsoderling WRT Addict

bsoderling

Posted
  • Author
Posted

Makes sense...

My balance wheel is of the closed type but I guess the process shoudn’t be that different?

To hold the opposite arm firmly without gripping the wheel, I guess I could modify a pair of pliers to go over the wheel and just grip the arm?

And the ”handle” with slots could then slide onto the arm to be bent and use as a lever to bend the arm? The narrowest slot fits nicely on the arm of my wheel.

I was hoping that I could do all this with the wheel in the tool to get quick feedback but it may be asking for trouble...






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JohnR725 Distinguished Member

JohnR725

Posted
Posted

because balance wheels  truing can get complicated I have a link. go to the bottom of the page Joseph School of Watch Making you'll see a section on balance wheel truing.

I have an image from the book to understand the key feature of the tool. Notice how the staff is resting on the conical  or cone part of the staff as the book calls it? then the tool needs to be adjusted so it's holding really tight. That means there is a zero danger of breaking the pivots off your supposed to true the balance wheel in the truing caliper. other things to watch out for sometimes truing calipers have holes on both ends for different size balance wheels. If you don't have that clearance you'll break the pivots off. So you have to be on the cone of the pivots. then not all the schools will have a double set of holes. Sometimes the other end is used for truing wheels. Other things you want to check on make sure your holes really are clear and that somebody didn't break something off before you.

then just to review things you may want to look the other sections on staffing.

http://www.mybulova.com/vintage-bulova-catalogs

bwtc.JPG

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bsoderling WRT Addict

bsoderling

Posted
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Hi and thanks for this interesting article (and website).

It seems my initial thoughts on the usage of the tool were not that far off. The explanation for the through-holes in the pivot holders make sense, I just wonder why my tool only has them on one side?

After ensuring that the wheel is resting on the pivot shoulder the truing operation is done by finger-force and there’s no mentioning about issues with breaking the staff rivet from this so I guess it should be fairly safe, assuming I got the riveting done properly.

I will find a couple of scrap balances to practise on and see how it goes....

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