This is the central and essential component of a watch case. Typically, the movement is fixed in the middle part and perfectly protected. The lugs can be attached to it (soldered or even screwed) or directly cut from the same block of material. The middle part serves as the anchoring point for most other case elements, such as the bezel and case back, for example. Like the case, the middle part can take various forms (round, square, barrel-shaped, polygonal, etc.). The outer wall of the middle part (circumference) is referred to as the “middle band.”

The middle part first appeared in the 17th century with the early developments of pocket watches. The middle parts were crafted by specialized artisans. That is why between the 17th and 19th centuries, many of them mastered the mechanical fabrication of cases, as well as the enamelling technique that was used to decorate the most prestigious watches of the era. With its reputation established as early as the 16th century, Geneva became the epicentre of such crafts, and the virtuosity of its watchmakers “cabinotiers” often remains unmatched to this day.

An artisan can handcraft a middle part using a lathe and milling machine. This method is still practised by a few watchmakers to produce unique pieces or very small series, or even for prototyping.

Today, machining is the most commonly used method for middle part fabrication. In such cases, machining centres are employed. This method is used for both small and large series. Modern machining centres enable automated production and perform all manufacturing steps except for polishing and assembly. It is also the method that allows working with the widest range of materials. This method is considered industrial when production volumes reach certain quantities. When the case is machined using this method, the lugs are often soldered to the middle part.

When it comes to producing middle parts in very large quantities, stamping remains a highly competitive high-quality solution, despite being one of the oldest techniques used in watchmaking. Unlike machining centres, which require long hours of setup and programming, stamping allows for very rapid production implementation. The higher the volume, the lower the costs. Quality remains constant and precise even after years of stamping. Unfortunately, not all materials are eligible for this method.

The advent of plastic materials, composites, and even synthetic sapphires, has involved new technologies. Injection moulding processes are still predominant in some cases. They can lead to a finished product in certain cases, while in others, machining and/or polishing steps will be necessary. The evolution of materials and technologies should see the emergence of new processes in the near future, such as photolithography and 3D printing, among others.