THE VARIOUS TYPES OF JEWELS AND THEIR FUNCTIONS
The jewels of a finely made watch are not the decorative type that one may find on the outside of a watch case but the jewels that are within the movement of the time piece itself. The jewels are used within the watch movement to eliminate friction as much as possible.
By the jewels reducing friction within the movement, the watch can run smoother and thereby last for far longer periods of time than it would otherwise be able without jewels. The jewels are hard and quite smooth and provide the proper friction free movement needed to assure a watch operates as finely as it was designed to.
Ammonia and aluminum are used primarily to manufacture and produce the faux rubies that make up the jewels of a watch. The deep red color of the ruby goes through several processes including a heat and chemical processes that end up transforming the piece into something known as boule.
After the creation of the boule, the process can continue with as many as fifty different operations from the cutting or sawing of the boule to polishing it to a high gloss so that it is hard enough and smooth enough to prevent any friction within the mechanism.
There are several types of jewels used within the watch mechanisms and the jewels themselves are only a millimeter or two in size with the holes drilled in them so small as to be barely seen by the human eye.
HOLE JEWELS – These jewels are made with garnet or ruby and resemble a traditional donut with a hole drilled into the center of the jewel. The cross section of the hole of this jewel can be in either of two fashions. It can be rounded, which is known as an olive-hole jewel, or the sides can be straight which is called a plate jewel.
The polished tip, or the pivot, of a wheel arbor, or the axle like mechanism for each of the watch’s gears, rides right in the hole of the jewel. The jewel provides the nearly friction free operation which lets the watch rely less on the power of the mainspring and can protect the parts of the watch from prolonged wear or damage.
CAP JEWELS – Cap Jewels are also known as end stones. The cap jewels are small jewel discs that fit over the hole jewel. There must be a hole jewel in place in order to have a cap jewel. The wheel pivot will be conical if there is a cap jewel in place. If the jewel is uncapped, however, then the wheel pivot will be square shouldered.
The wheel pivot will ride along the cap jewel when the jewel is capped and the hole jewel will stop it from veering from side to side. Again, the aim is to eliminate as much friction as possible and to keep any contamination from the outside at bay. When capped jewels are present on the escapement of a particular watch, the watch will have a greater range of positions and will deliver a more consistent performance than if the watch just has a hole jewel. Sometimes cap jewels are made from diamonds.
PALLET JEWELS – Attached to the pallet fork, usually with shellac that has been melted, the pallet jewels look similar to a long block and are all angles. The jewels will then function with the escape wheel’s teeth. There is the entry pallet jewel and there is the exit pallet jewel within the watch. Each takes a turn and alternates with engaging the gear train and then will transfer impulse power to the balance of the watch. The transference happens through the impulse jewel.
IMPULSE JEWEL – This is a garnet or ruby pin jewel and when it is stood up on its end it will resemble an upper case letter D. This impulse jewel is found on the roller table of the balance and the standard watch will generally have just one of these. This jewel will oscillate in a back and forth motion as the balance is turning. This will allow the pallet to unlock. The pallet unlocks, the escape wheel advances tooth by tooth, and the escapement of the watch is thereby regulated. The impulse jewel becomes the contact between the gear train and the balance of the watch. The melted shellac is what usually holds the impulse jewel in place in vintage watches.
DO MORE JEWELS DETERMINE THE QUALITY OF THE WATCH?
The more jewels the better the quality seems to be a standard rule of thumb but it is erroneous. The more jewels a watch has does not necessarily indicate a higher quality watch. There does, however, tend to be a parallel between finely made high quality watches and the number of jewels they contain.
Jewels on the wheel of the gear train will ensure that the watch will run longer and more efficiently as watches without the jewels placed there will wear down much more quickly over time. This occurs when the steel arbor of the gear continuously grinds and eventually slices its way into the brass plate. This will cause the arbor to move because the holes will become larger over time thereby causing the watch to break down sooner than it should. Brass bushings will wear away much more quickly that jewels will.
What is truly needed for a quality time piece is for the power from the mainspring to the escapement to be as efficient as possible. Because of the jewels, the mainspring in a watch can be thinner and a bit longer which will increase running times. Finer watches tend to have 17 or more jewels rather that the 7 or so jewels that lesser quality watches will have.