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What lies beneath...

2011-02-13 00:03

You've got a good watch, probably made in Switzerland or Japan, and on the dial it says '17 Jewels' - or perhaps a chronograph, with its multitude of subsidiary dials displaying the time in six countries, stop watch, yachting timer, who won the world cup in 1954 - now that could easily have 23 jewels or even more.  But what do all these jewels mean? James Went answers some frequently asked questions.

Where are the jewels?  For a start, they're not visible - unless your watch has a glass underneath to view the movement.  Even then, it will only be possible to count less than half the jewels - they're the small rubies set into the metal plates and most of them hold the gears (or 'wheels' as watchmakers call them) in position.

Why have them?  The wheels rotate on hardened steel pivots.  In non-jewelled watches these pivots eventually wear the plates of the watch (made of softer metal) and the timepiece needs repairing before too long, no matter how well it's been oiled.  If the steel pivots rotate in a ruby ring however, there is negligible wear because rubies are only surpassed by diamonds in hardness.

Who first used jewels? Nicolas Fatio was a Swiss protestant who fled from France to London after the Edict of Nantes was revoked in 1685.  He was a well-educated sort, being a mathematician, astronomer and optician as well as having an interest in watchmaking.  Fatio and a fellow refugee Peter Debaufre, a French watchmaker, invented a method of piercing rubies for use as watch bearings and applied for a British patent in 1704. 


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The patent was soon withdrawn when the Clockmakers' Company raised fears that paying royalties to the inventors could only be enforced in Britain;  British watchmakers would be put out of business by having to pay for the privilege of using the process, whereas other countries would pay nothing.  It seems hard to believe, but the method of making jewelled bearings was kept secret for many decades until the process was eventually developed elsewhere in Europe.

Are the jewels valuable? Since the beginning of the 20th century, synthetic rubies have ousted the natural stones in watch manufacture.  There is no difference in composition between the two except that man-made rubies are flawless and much better suited for bearings.  Synthetic stones for watchwork retail at one or two euros each before tax.

What does 'Fully Jewelled' mean?  There must be at least 15 jewels before a watch can be described in this way, although most watches these days will have 17 as a minimum.  All the jewels counted must have a function in the watch movement and not be there simply to increase the jewel count!

Are all jewels the same shape?  Most jewels are like tiny rings (jewel holes).  Two or four will be flat or domed discs (end stones).  Two are wedge shaped (the pallet stones) and one is "D" shaped (the impulse stone).  There are variations in some watches, for instance Omega models featuring the co-axial escapement.



'You can have jewels in any colour, so long as it's red'  This adaptation of Henry Ford's quote does not always apply to timepieces!  Early watches may have natural rubies which can be pink or colourless.  Even synthetic stones can be produced in pink, blue, or other colours - however, red remains the norm.  Whatever the colour, whether the stone is described as a ruby or sapphire and whether it is natural or man-made makes no difference to the composition - all are corundum (aluminium oxide) with added colour.

My watch is marked 'Incabloc' - what does it mean?  If a watch is accidentally knocked there is a good chance the very fine pivots on the balance will bend or break if they are held rigid.  Incabloc is a shock-absorbing device invented in 1934 allowing the balance jewel holes to move sideways with the pivot when necessary, preventing any damage.  Many other similar systems were developed during the 20th century, Kif being another commonly encountered.

Do clocks use jewels?  Carriage clocks and others that have balances will have between three and eleven jewels in the escapement.  'Floating balance' clocks produced in the 1950s and 1960s have two jewels which rotate with the balance.  Some 19th-century French clocks have a visible escapement inside the dial, and these can have carnelian jewelled pallets, orange in colour.  It is rare for clocks to have large jewels, but some regulator clocks (such as those currently made by Erwin Sattler) have agate or ruby pallets and ruby bearings fitted.

Finally, how about my quartz watch?  Jewelling isn't so necessary in these watches because the gear train, rather than being in constant motion, pulses every second or every 20 seconds.  Some high quality quartz watches are jewelled, but the advantage of jewelling is of greatest benefit in spring-driven timepieces.

James Went is a member of the British Horological Institute and the British Watch and Clock Makers' Guild.

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