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Re: How to disassemble a Chronomatic movement

Hi Craig,
Thanks for your kind words.

About the unwinding of the mainspring, I tend to work on a watch when is already wound down, but even so the mainspring still has a small residual torque... so once the automatic gears train and the stopclick 1428 is removed, only the click 425 prevents the mainspring to be unwound, so if you open gently the click 425 with a screwdriver with the left hand and simultaneously take the crown on the right hand (before removing the intermediate ratchet wheel 417) you will easily unwind the mainspring controlling the residual torque via the crown; instead, if you will already have removed the 417, opening the click 425 the ratchet wheel will unwind shortly but, being the mainspring already almost wound down, the ratchet wheel 415 will tipically do not more than half a turn (8 complete turns of the ratchet wheel corresponds to a fully wound mainspring).

About the balance wheel, there is no specific reason to remove it at the end and your suggestion is correct...I know that some watchmakers don't even remove it (leaving the balance and the pallet fork in place during the cleaning phase), but I prefer to remove everything to better clean the pallet fork's pivot jewels as they will not receive any oil (so must be super clean to have a proper oscillation amplitude).

Last but no least, there are two steps that I hate during a service, that are reinstalling the jewel cap into the Incabloc (happened to break a lyra spring and to reinstall a new one is necessary to remove completely the Incabloc assembly from the balance cock) and oiling the impulse plane of the exit stone of the pallet fork via the inspection holes of the mainplate (almost impossible to oil exactly the impulse faces without spreading the oil also on the top surface of the pallet stone, damn!).

All my best.


Congratulations - this is a difficult task to take on, especially
: with a movement like the cal 15. A couple of questions - was the
: movement already wound down when you started or did you have
: some way that you let the mainspring down before removing the
: 1142 bridge? Most movements were made so that the mainspring
: could be easily let down prior to disassembling but not the cal
: 11 - 15. My other question is why was the balance not removed
: 1st to avoid any damage to it during the rest of disassembling?
: Having damaged a balance or balance spring with the slip of a
: screwdriver is something I have personally experienced more that
: once. Anyway, this is very good documentation with great pics.
: You have put many hours into this - thanks for sharing.

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