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HANDS

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1. General description

The hand is a pointer whose tip travels circularly (e.g. the minute hand), linearly or randomly (e.g. the power reserve indicator hand), over the scale dedicated to it, which is printed, most of the time, on the surface of the dial.

Although they can be made from various materials, the hands are generally made of Metal (Brass, Gold, Steel, Aluminium…). Depending on the production method chosen, their shape, function or complexity, hands can be made in one piece, two pieces, or even more.

The hand is fixed to the wheel that drives it via its pipe (tube), press-fitted (tight fit) onto the end of the wheel’s pivot, or onto the pipe of a wheel or pinion (minute hand on the Cannon pinion, hour hand on the Hour wheel). The stamped or applied hand pipe carries the hand’s blade, the tip of which points to the indicated value. In some cases, in order to optimise the watch’s operation, the hand includes a counterweight.

A large number of finishes can be applied to hands, such as diamond polishing, polishing, satin finish, sandblasting, etc. Hands can also be partially or fully painted, or coloured using galvanic processes or by vapour deposition (PVD, DLC, CVD, etc.). For night-time reading, the hand can be given a photoluminescent material (Superluminova).

2. History

When the first mechanical clocks appeared at the end of the 13^th century, they had neither Dial or hand. These clocks were initially limited to striking a specific hour of the day, then, from the early 14th century, the 24 hours of the day. It was at the dawn of the 15^th century that the first dials fitted with a single hour hand appeared. Mechanical horology then progressed rapidly. The 24-hour dials then gave way to more legible 12-hour dials. When Christian Huygens finalised the theory of the pendulum in the mid-17^th century, the accuracy of clocks improved considerably and the first minute hands soon appeared.

Travel clocks and watches would naturally adopt this mode of Display. The style and shape of hands would evolve over the centuries, frequently providing valuable information about the period in which the clocks or watches they animated were made. It was not until the dawn of the 20^e century that the Hand underwent its most significant evolution thanks to the application of radioluminescent material (radium). The high radioactivity of this material and its dangers were known as early as 1920 (the radium girls affair). However, in Switzerland its use was not banned until 1963. Radium was then replaced by tritium, whose radioactivity poses no danger to humans, but whose luminescent properties are, in fact, lower than those of radium. It was not until 1994, with the invention of Luminova, that radioluminescent materials were replaced by photoluminescent materials. By definition, Luminova releases the light to which it has been exposed, acting like a battery. Its night-time luminescence is therefore limited over Time. However, its light intensity is high and has continued to improve since its invention.

3. Semi-industrial production of hands

An alternative to artisanal and industrial methods, particularly interesting for small series or hands with complex profiles, consists in cutting the Hand by wire electrical discharge machining. All the Materials that conduct electricity are eligible for this technique, which allows several hands to be cut during the same cycle (stacking of material). This technique also makes it possible to create very fine and complex cuts without any mechanical stress being exerted on the hand, and requires the pipe to be added, then riveted at a later stage. The cut hand then receives its finishes according to the desired result (Polishing, Sandblasting, Satin finish etc.) and can also be diamond polished.

From then on, the pipe can be riveted onto the plate. With the exception of hands made of Gold, the hand then receives its colouring. Depending on the desired result, the colouring can be obtained by painting, by galvanic treatment, by eloxal treatment (anodising) (for Aluminium) or by vapour deposition (PVD, DLC (Diamond-Like Carbon), CVD, etc.). If needed, the luminescent material is then applied to the underside of the hand. The luminescent paste fills, by capillarity, the window created for this purpose during the first cutting step. Finally, dimensional and aesthetic checks are carried out on each hand before it can be packaged for the final assembly of the watch.assemblage final de la montre.

4. Industrial production of hands

The base material comes in the form of a strip, with a thickness slightly greater than the final thickness of the hand blank.

Stamping of the Pipe
The first step consists of forming the Pipe by stamping when it is not applied separately. For Hands intended to receive luminescent material or for openworked (or skeletonised) Hands, a first cut of the Openworking is carried out using a Balance press and cutting tools (Die and punch).

Stamping of the Hand
The next step consists of cutting the outer contour using the same process.

Diamond polishing and Polishing of the Hand blank
The upper surface of the blank is then diamond polished to give it its final shape (flat, rounded or faceted) and to give it a Polished appearance. Other finishing operations may follow, such as a fine Polishing, a Satin finish or a Sandblasting partial or total.

Riveting of the pipe (when postponed)
It is after this step that the pipe is riveted to the plate for hands with an attached pipe (seconds hands and counter hands). With the exception of hands in Gold, the hand then receives its colouring.

Finishes
Depending on the desired result, the colouring can be obtained by painting, by galvanic treatment, by processing (anodising) (for aluminium) or by vapour deposition (PVD, DLC (Diamond-Like Carbon), CVD, etc.). If necessary, the luminescent material is then applied from underneath the hand. The luminescent paste fills, by capillarity, the window made for this purpose during the first cutting step.

Quality controls
Finally, dimensional and aesthetic checks are carried out on each hand before it can be packaged for the finalAssembly of the watch.