Friction. It’s always slowing us down.
The same holds true for watch movements, mechanical and quartz. It didn’t take long for watchmakers to realize that friction created by the interaction of moving parts within mechanical watches distorts the functionality of the watch by distorting accuracy.
Enter watch movement jewels.
Interesting Note: The sound of a watch ticking is actually two jewels hitting the teeth of the escapement wheel.
Jewels In Watches?
I’m sure that at one point or another you have noticed ’21 Jewels’ on a watch face.
Without much watch knowledge, you might think this indicates something special that sets a particular watch apart from others: it has jewels, therefore it must be special or valuable.
But what does it really mean?
Pre-1902 natural jewels were used in watchmaking but that changed with the advent of the synthetic counterpart. The jewels used in watches are synthetic sapphire (corundum). Corundum was used because of the ability to produce large quantities at relatively low prices (a few cents per jewel).
Why jewels (synthetic) are needed in watches:
- Metal on metal creates large amounts of friction and material wear
- Metal on jewel does not create much fiction and the hardness of the jewel allows it to be unharmed
- The low cost of synthetic jewels significantly increases the profit of a watch as opposed to using natural jewels
Important Note: All watches have jewels. Also, the jewels used are not the most precious unless otherwise noted by the manufacturer.
Where’s The Treasure?
The most common jewel counts are 15,17,19 and 21.
Each moving part of the watch must be ‘grounded’ by a jewel that reduces the friction and wear and tear on a metal piece that would occur. For example, each gear axle is held in place by a jewel at either end.
A typical "fully jeweled" time-only watch has 17 jewels:
- 2 cap jewels
- 2 pivot jewels
- 1 impulse jewel for the balance wheel
- 2 pivot jewels
- 2 pallet jewels for the pallet fork
- 2 pivot jewels for the escape wheel
- 2 pivot jewels for the fourth wheel
- 2 pivot jewels for the third wheel
- 2 pivot jewels for the center wheel
Ken Aiken provides a great overview of the different types of individual jewels that are used in watches.
The more moving parts there are, the allowance for more jewels. Thus, automatic watches usually contain 21.
Functional Jewels vs. Non-Functional Jewels
Functional jewels are an integral part in the precision of the watch. These include the jewels needed for the mechanism to be efficient. Without these jewels, the mechanical features of the watch would deteriorate faster disrupting the whole mechanism.
Non-functional jewels are additional jewels that do not really serve any purpose other than for some aesthetic benefit:
- Some manufacturers may market a watch to have more than the ordinary amount of jewels constituting a higher price.
- Or additional jewels are placed where they do not serve any purpose but are said to help overall friction reduction.
Interesting Note: There have been many attempts to pack as many jewels into a wristwatch as possible including a mechanical 100-jewel watch.
Does beauty constitute price?
Watch jewels serve one purpose: keep the watch accurate and lengthen the life of the watch parts.