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Hamilton 917 hairspring terminal curve?

Dawagner

By Dawagner
in Watch Repairs Help & Advice

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Dawagner Member

Dawagner

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Hey WRT,

Ive got a Hamilton 917 movement I am working on to get better at my hairspring techniques.  I was wondering if anyone had a link to a good copy of the terminal curve diagrams and knew what terminal curve these movements are supposed to have?  Pretty much the terminal curve is the only thing messed up on this piece and would like to try and fix it instead of replacing it.  Thanks!

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praezis Super WRT Addict

praezis

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Hi,

the curve is determined by the ratio "distance of the regulator pins from center" to radius of the hairspring. Multiplied by 100 gives the curve number (eg 75) that you can look up in tables. If still needed, I can post one next week. 

Frank

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Orville New Member

Orville

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Amazing answer by praezis above.  I never knew.  When I was super focused on hairspring manipulation as a learning module, I could figure out the termination by the sweep of the regulator and get it right most of the time. The important thing is that if it's not dead on, it's dead off.  Maintaining the coil of the spring is another key.  Distorted hairsprings don't work and I have a boxfull of them to prove it.  

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praezis Super WRT Addict

praezis

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Just found one in an older post of mine.

There were different authors of overcoil diagrams with different design, but they all match the theoretical rules.
These are from Helwig, Glashutte.
You must size the picture so that the diameters match your vibrated hairspring. Length of the overcoil (from knee to regulator pins) is about 180° of outer coil.

Regards,

Frank

kurventafel_helwig_gl.jpg.b4cdf4d78fec52b6296895bbb02fa454.jpg

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Dawagner Member

Dawagner

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Perfect thank you sir, yes I am taking about a breguet overcoil.

Any tips you have for redoing one? The spring was fairly mangled and there was no good way to save what bends were in it so I have made it back to flat and concentric in preparation of redoing the terminal curve overcoil.

Thanks again!

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praezis Super WRT Addict

praezis

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Hi,
Making an overcoil is one of the most challenging tasks in watchmaking.
I recommend finding a book that discusses this topic. Surely other members can help, as I know mainly German literature. 

Essential for bending are special curve tweezers with )) tips. New ones are no more made today, you can find them used or make your own. 

Frank
 

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