How to distinguish a good watch from its movement: How to appraise a high-quality watch (gears)

The standards for what makes a "good watch" vary from person to person. However, some easily identifiable points include the finish and construction. This article explains how to "distinguish a good watch" from these points of view in "How to Appraise a Good Watch." This time, we will focus on the gears, which play an important role in both functionality and aesthetics.

A summary of "How to identify a good watch" - a deep explanation of "How to identify a good watch"

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A good watch from the perspective of its gears

　The speed adjustment mechanism featured in the previous articleGears are not as noticeable as other components, but they play an important role. For mechanical watches that operate with low torque, the quality of the gears can make a big difference in performance. Some manufacturers also improve the aesthetics of their movements by polishing the gears. Let's take a look at the gears and their finishes used by various companies, focusing on NIHS gears, which have become popular in the watch industry.

Gear tooth shape

　Gears are extremely important in terms of both aesthetics and functionality. They consist of a pinion with teeth cut around an axis, a wide wheel, and a pinion on a thin axis.

　High-end watches generally use finger-shaped cycloid gears and their improved version, the NIHS gear. This tooth profile is typical of high-end Swiss-made watches, with minimal torque transmission loss and a shape that is reminiscent of a luxury watch. Furthermore, because it is an industry standard, cutters for cutting the teeth are easy to obtain. However, it seems that even the NIHS gears were not perfect in terms of drive efficiency. Currently, new tooth profiles with higher drive efficiency, such as the SPYR gear, jointly developed by Germany's DIN and 12 Swiss watch manufacturers, are also used.

Audemars Piguet "Cal.4302"
While the Caliber 4302 has a modern design, the gears (wheels and pinions) use the classic NIHS movement. It's only natural that a company that avoids adopting new materials would use standard gears from the Swiss watch industry. The teeth are made of gold-plated brass. The finish is the same as that of high-end watches in the same price range, but Audemars Piguet has given the pinions that mesh with the wheels a black polished finish, allowing the light from the pinions to reflect on the wheel.

Vacheron Constantin "Cal.1400/1"
As far as I know, almost all Vacheron Constantin watches use NIHS gears. They are very classically made, but what makes them different from older movements is that the rims of the wheels are thicker. Movements from the 1940s and 50s would have had thinner gears. There are various theories as to why this is the case, but some say that one factor is the increased vibration of the movements. As you would expect from a high-end watch, the finish beyond the gears is impeccable.

　Jaeger-LeCoultre, which uses the SPYR movement, emphasizes its advantage of smooth torque transmission rather than high drive efficiency. However, its appearance is almost identical to the NIHS. Furthermore, since drive efficiency can be dramatically improved by using a lighter escapement, the method of using gears to improve drive efficiency is no longer popular. The exception is Omega's Cal. 3861, released in 2019. This uses a tooth profile with high drive efficiency that is an improvement over the NIHS. Japanese manufacturers, however, have much more freedom in gear design than Swiss manufacturers.

Patek Philippe "Cal.215 PS"
As is typical of high-end Swiss watches, Patek Philippe uses standard gears. Some models use a new tooth profile called SPYR, but the Cal. 215 PS, whose basic design dates back to the late 1970s, likely uses the same NIHS type as before. As is typical of high-end watches, the arms that make up the wheel section are chamfered, and the top and bottom surfaces are decorated with sunrays. While not shown in the photo, the pinions are also polished, of course.

Chopard "Cal.LUC 98.01-L"
The Quattro, which has four barrels, also has a solid wheel connecting the barrels to the gear train. It is made of gold-plated beryllium copper. This material is harder than brass, so it is used in parts that are subject to stress. These wheels are usually plated and then have their teeth cut with a cutter, so the precision of the parts' processing is easily apparent. Although it is a little hard to see, pay attention to the extremely smooth teeth. Although it is an inconspicuous part, a watch with carefully finished teeth and pinion sides is undoubtedly a high-end watch.

　ETA-type gears are becoming more common in cheaper models. These have a different tooth shape than NIHS, and currently there are profiles (tooth shapes) such as ETA73, ETA A, and ETA E. Roughly speaking, any car with a tooth shape that is as close to triangular as possible can be considered an ETA-type. However, even if it is not an ETA, manufacturers that are concerned with productivity tend to use triangular or similarly shaped teeth. Triangular teeth simply need to mesh together, and are not very efficient.

Cal. HMC321
While current H. Moser & Cie. watches use NIHS gears, the movements they designed previously used DIN gears, which are more efficient than NIHS gears. While the differences in appearance are subtle, they were undoubtedly a major feature of Moser's watches of the past. Unfortunately, the chamfering is diamond-cut, but the movement still boasts impressive details, such as nearly Mi-Glass-cut hole jewels, mirror-finished pinions, and black-polished screws.

H. Moser & Cie. "Endeavour Small Seconds"
This model is a near-unchanged successor to the previous "Mayu." The price has gone up, but it is justified as the quality of the parts that cannot be seen has also improved. It features the fumé dial, a distinctive feature of H. Moser & Cie. The impressive movement remains unchanged in this model. Manual winding (Cal. HMC321). 28 jewels. 18,000 vph. Power reserve of approximately 3 days. 18KRG case (38.8mm diameter). Water resistant to 3 bar. (Inquiries) East Japan Tel. 03-6274-6120

　In terms of aesthetics, the gears used in the gear train should be cycloid and NIHS types. In particular, gears with long tooth depths (the distance between the tips and roots of the teeth) and narrow pitches (the gaps between the teeth) give the watch the appearance of a high-end watch. In contrast, ETA-type gears, no matter how they are finished, do not look very attractive.

Commonalities between the gears of luxury watches

　Aside from the tooth profile, the gears of luxury watches share a common requirement: the pinions and pivots are perfectly polished, and in the highest quality models, the pinions are black polished. However, this is not to reduce resistance, but rather to make the entire gear train shine brightly when exposed to light. This is a useful technique in thick, complicated watches, as it adds depth to the movement.

Cal.SXH1
This movement features an asymmetrical design. Although the price is modest, the deep, hand-chamfered edges have a sharp edge, and the matte finish on the plate and bridges is quite delicate. The two hollowed-out ratchet wheels also have a ring pattern on the top and are slightly chamfered. Considering the price, this is more than enough detail. It is a great example of a very conscientious watch.

Capek "Quai des Berg No. 25"
A masterpiece that combines excellent finish, practicality, and a strategic price. The movement was developed in collaboration with Jean-François Mojon, head of Chronode. The price is astonishing considering its features. Manual winding (Cal. SXH1). 31 jewels. 21,600 vph. Power reserve of approximately 7 days. XO steel case (42.5mm diameter). Water resistant to 5 bar. (Inquiries) Noble Styling Tel. 03-6277-1604

　Furthermore, high-quality teeth are gold-plated, have a certain thickness, and have a circular pattern on the surface. Even a movement with ETA-type gears would look impressive with this type of finish. In addition, chamfering the inside of the arms that correspond to the teeth's meshes would give it a more high-end look. In the highest-end models, the wheels themselves are made of gold instead of brass, but Voutilainen is probably the only company that uses this in current models. While gold teeth have no practical use, they have the effect of focusing light on the gear train, just like black-polished pinions.

How to identify gears

　❶ is an involute gear used in a variety of industries. It is particularly used in automobiles because it can withstand large torque and is highly manufacturable. However, because torque transmission is uneven and drive efficiency is somewhat low (said to be at least about 90-92%), it is not generally used in watches that operate with small torques. However, some designers consider mass-produced gears (ETA type) to be a hybrid between involute and cycloid, which will be discussed later. In the case of mass-produced machines, cost constraints are greater than in high-end machines, so the shape of the gear will likely be simpler.

　❷ Cycloid gears are used in luxury watches. The Swiss NIHS gear, perfected in the 1960s, is one such type. While it is said to have higher drive efficiency than involute gears (said to be up to 95%), some designers, such as François-Paul Journe, believe that "the transmission efficiency of cycloids (and ETA-type gears) and involutes is the same." The German DIN and SPYR, which became popular after the 2000s, are also types of cycloid gears. However, the cycloid gears used in the watch industry are not strictly cycloids, either. In fact, documents from the 1950s describe the gears used in watches as merely "cycloid-like." Furthermore, since the NIHS was designed in an era before computers, the tooth shape is processed graphically. Currently, various manufacturers are working to develop their own highly efficient gears based on cycloids.