Why do watch movements use rubies?

　　The rubies used in ruby bearings as we call them are generally synthetic, primarily composed of aluminium oxide. They feature characteristics such as a hard and uniform texture, ease of machining, and a wide variety of colours, sharing the same properties as natural rubies. I wonder if you have ever considered why watch movements are embedded with rubies?

　　1. Historical Background

　　Let us start with the history of rubies. 18-century Britain was the cradle of high-quality clocks, where watchmakers used small particles of ruby (known as jewels) as bearings for balance pivots. The ruby drilling technique was first invented by Nicolas Fatio, a Swiss optical instrument maker and astronomer, who went to Britain hoping to secure a royal patent for this invention. However, the British claimed that the technology was already in use, and he ultimately failed to obtain the patent, though his technique was adopted by other craftsmen. It was precisely this technology that allowed the British Empire to maintain its leading position in the watch industry. The turning point came with the master watchmaker Abraham-Louis Breguet, who brought British watchmaking technology back to France. Since then, rubies have been widely utilised in watches.

　　2. Technical Reasons

　　The setting of rubies in movements was initially based on technical reasons, as the operation of a mechanical watch movement relies on the continuous transmission of power through various gears. Before the vital function of rubies was understood, the pivots of the escape wheel, the pallet fork, the balance staff, and the wheels of the gear train were pivoted directly into holes within the brass plates. These holes featured small oil sinks where oil flowed in to lubricate the pivots. Over time, dust and other particles from the air entered, forming an abrasive substance that gradually wore away the softer brass of the plates and even the harder steel pivots. Watchmakers thus realised the need to find a material harder than brass that could withstand the wear of the pivots. This material was the ruby, a substance second only to diamond in hardness. Natural rubies are highly scarce, so synthetic versions are produced for use in watches.

　　3. Consumer Demands

　　All products ultimately exist to satisfy consumption. In the eyes of consumers, timepieces featuring gemstones (even synthetic ones) enhance face value and prestige. Watchmakers quickly caught on to this business opportunity and began setting rubies into movements. Ruby bearings mainly fall into four categories: one is used as pivot holes, commonly known as jewel holes, which are set in specific parts to bring the wheel axle and the jewel hole into contact; another is used as cover plates, commonly known as endstones, which act like mechanical bearings to limit the vertical play of the pivots; yet another is the circular diamond used as a pallet jewel. Even in an ordinary manually wound mechanical watch, the number of jewels can range from a minimum of 14 to a maximum of 19, while automatic winding and complicated mechanical timepieces have even more.

　　Conclusion: Rubies undoubtedly enhance the overall quality of a product, and high-quality watches certainly cannot do without them. However, the Watch World editor would like to remind everyone to avoid falling into the misconception that ruby bearings are the exclusive preserve of high-end watches. With the spread of industrialisation, the use of ruby bearings in watch movements has become very common. At the same time, a large quantity of rubies does not equate to high quality; truly high quality is something that has weathered the test of time and survived.