To my admittedly devious mind, the “positions” specified in watch adjustment conjure up an image of a plush, dimly-lit room somewhere in a watch factory where couples of workers are checking the correct functioning of watches while engaged in a variety of Kama Sutra positions.
Alas, the reality is much less colourful. A watch adjusted to four, five or six positions means that its accuracy has been tested in that many orientations. This is necessary because gravity affects a movement in different ways according to its position. The detrimental effects, increasing friction and changing balance oscillation rate, are greatest when the balance spring is in the vertical plane.
The adjustment positions are based on the most frequent positions of the watch during normal wear. For wristwatches, the first two positions are horizontal, dial up, dial down. These are followed by the vertical positions, crown down, crown up, and crown left. In real life, these correspond respectively to when your hand is hanging down, when your forearm is vertically up (elbow on the table, perhaps with chin on your hand in the so-called “bored office worker” position), and forearm horizontal. The sixth position is crown right. Most movements today are adjusted to five positions, and so this position is omitted. Even though it may seem commonly used – in the vertical plane, crown right, and so in the classic frontal image of the watch – this in actual fact occurs only rarely during the day. It would mean raising your wrist horizontally in front of your eyes to check the time.
The five positions listed above are also the positions used by COSC when testing movements. Here are photos of all six, shown with a watch mounted on a watch repairer’s microphone that can be rotated to the different angles:
In the past, many watches were adjusted to three positions, dial up, dial down, and crown down. The positions were different for pocket watches, typically dial up, crown up, crown right and crown left, reflecting the way they spent most of their time: lying on the bedside table at night, and vertical during the day..
Watch repairers may use a different set of adjustment positions, typically dial up, dial down, crown down, watch inclined at 45° with dial down, watch inclined at 45° with dial up.