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Chronometers are part of a special area of horology.  Their purpose as instruments of extreme precision used for navigation at sea meant that great expectations were placed upon their performance and reliability, after all lives depended on them.  As such chronometers are some of the finest examples of the skills of the watchmaker.  The quality of workmanship is second to none and must be handled very carefully.  For the working life of a chronometer it would be handled by skilled specialists only and would leave the repairers hands with a rating certificate to prove its capability’s.  With the advent and introduction of GPS systems Chronometers ceased to be relied upon and often began to languish on dusty shelves.  It was at this time that a Chronometer may have succumbed to less skilled intervention to “just get it going”.

For much of its life this example had been beautifully cared for, however it had more recently succumbed to work that has done more harm than good.

When received, the Chronometer was running, albeit with a very low amplitude.  The oil was very dirty and it was due for a full once over.  When inspected closely it became clear that work had been done to correct faults with minimal tooling and parts.  The escape wheel pivots had been broken at some time.  Instead of re-pivoting, new pivots had been turned onto the shortened arbor.  The jewels had then been removed and rather crude extended bushes fitted in their place.

The balance staff had also seen damage to the lower pivot especially.  This had meant that the escapement had been ‘fiddled with’ to correlate with these modifications.

To correct this work the escape wheel arbor was drilled and an extension piece fitted.  This was then turned down and a new pivot turned at the correct length.  The bushes were removed and jewels re-instated with screwed chatons as original. The balance staff was also extended and new pivots turned.

The escapement then required complete re-adjustment to bring everything back into line and restore the best possible action of the escapement.

The rest of the movement was in excellent condition and responded well to the usual sensitive overhaul techniques.

Following restoration, the Chronometer now performs very well with an excellent amplitude and gives reliable performance.  Perhaps their sea fairing days are over but that doesn’t mean we can’t cherish these precision objects and care for them as their makers would have wanted.

 

Christopher T Jobson

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