Regulating a watch movement for beginners

Mechanical watch movements consist of a large number of individual parts whose manufacturing precision determines, among other things, how accurate a movement is. In addition, external influences such as shocks or temperature changes contribute to the fact that a movement always shows a certain deviation from the real time. And aging processes of the lubricants and materials used also have their share.

ETA 6497-1 [source:]

Before we get started regulating, we need to define and contrast a few important terms:

  • The rate of a movement refers to the increasing or decreasing deviation of the displayed time from the real time within a day. By observing this deviation over a longer period of time, one can determine the average daily rate of a movement. The rate depends, of course, on the wearing behavior, since movements, shocks and temperature changes have an influence on it.
Rate of a movement in the position dial up on the timegrapher (0 seconds per day)
  • Regulating is the process of changing the rate. Either by changing the so-called effective length of the balance spring via the regulator or by changing the moment of inertia of the balance via small weights, often in the form of screws.
    If the rate is largely constant, you have a very precise movement in front of you. It only needs a little adjustment to show the correct time.
Regulating via a regulator
Regulating via sliding weight screws on the inside of the balance rim [source:].
Regulating via weight screws on the outside of the balance rim [source:].
  • Adjusting refers to measures aimed at achieving the most stable possible rate with regard to the position of the movement, the temperature and the isochronism (stable rate over the force curve of the mainspring). This includes, for example, centering and flattening the hairspring, balancing the balance rim, adjusting the regulator curb pins, but also optimizing the force curve of the mainspring. In many movements, the imbalance of the balance is corrected by the manufacturer by removing some material on the underside with a milling cutter or laser.

Balance wheel with milling [source:]

The terms regulating and adjusting are often used interchangeably, so it is not always clear exactly what is meant. Adjusting is the art of watchmaking; here, we will confine ourselves to regulating the movement. And even here, we limit ourselves to the case of regulating via a regulator, since this is most common in modern movements. Regulating via the moment of inertia of the balance requires much more experience, since adjustments must always be made synchronously on the opposite sides of the balance rim. Otherwise, you create an imbalance of the balance, which will certainly have a negative effect on the rate!

Before we get down to the practice of regulating, we need to familiarize ourselves with how the regulator works and understand why it’s better for beginners to keep their hands off the balance spring stud!

We do this on the example of the well-known movement Unitas / ETA 6497. In the following picture, the regulator is labeled with R, the balance spring stud with S and the regulator index with RZ.

Regulator R, Regulator Index RZ, Balance Spring Stud S

The regulator consists of a small lever, which is supported by a tightened ring around the upper balance bearing and can be rotated. On the underside of the regulator are two very narrow pins, the regulator curb pins, between which the outermost coil of the hairspring passes. The regulator curb pins limit the so-called effective length of the hairspring, i.e. the part of the hairspring that has a significant influence on the oscillation behavior.

The regulator index is connected to the regulator via a tensioned ring, so that moving the regulator index causes the regulator to move. When moving the regulator index, one usually has more feeling for tiny changes than directly on the regulator. However, there are also movements without a regulator index, such as the Miyota 9015, so that you have to move the regulator directly to adjust it.

Miyota 9015 without regulating index

The hairspring is a little longer than the effective length and ends in the balance spring stud. This therefore marks the outer fastening point of the hairspring. Ideally, the part of the hairspring between the regulator and the balance spring stud has no significant influence on the oscillation behavior of the balance. On older movements, the balance spring stud is firmly attached to the balance cock. On newer movements, however, it can also be moved. It is used to set the so-called beat error. In principle, this describes the asymmetry between the tick and the tock of the movement and should be as small as possible. And here is a big danger when regulating a movement: if you twist the balance spring stud instead of the regulator, you cannot correct this as a beginner without a timegrapher. In the worst case, the movement will not start at all. So fingers away from the balance spring stud as a beginner!

The following questions arise with regard to regulation:

  1. In which direction do I have to move the regulator to speed up or slow down the movement?
  2. How far do I have to move the regulator?
  3. What tool do I use to do this?
  4. How do you actually regulate a movement in several positions if there is only one regulator?

The question of the direction can be answered quite simply if you have internalized the following basic principle (learn it by heart!): if you shorten the effective length of the hairspring, the movement runs faster; if you lengthen it, it runs slower. If you turn the regulator in the direction of the balance spring stud, the effective length of the hairspring increases and the movement slows down. If you turn the regulator away from the balance spring stud, the effective length becomes smaller and the movement faster. This is how it looks in the picture shown above:

Faster and slower – this is how it works

How far do you have to turn to change the rate, for example, by plus or minus five seconds? Usually a fraction of a millimeter is sufficient! So start with small changes and then observe the rate behavior! With a timegrapher the control is very fast, without it takes some hours until you can judge the achieved change of the rate. Ideally, you should wait a whole day.

And what tool do you use for this? Professionals often use a small screwdriver. However, beginners slip off easily with it, so that its tip often ends up in the hairspring and screws it up! I therefore recommend such a stick made of plastic:

Bergeon 7010 plastic stick

In contrast to the screwdriver, the round tip has the advantage that it can be used to make delicate rolling movements to the side. But of course, extreme caution is also required with this tool!

The question remains, how to regulate a movement in the different positions. Typically, a timegrapher is used to determine the rate in the six positions: dial up, dial down, (hanging) crown up, crown down, crown left and crown right. Ideally, the differences in rate are very small. If they are not, the movement is not properly adjusted, which is not uncommon, especially with vintage movements. The layman cannot correct this! So the answer to the question is: the movement can only be regulated via the regulator in such a way, that deviations between the positions become as small as possible and the movement shows an acceptable rate when worn. For example, if the movement has a rate of -9 seconds per day in the dial up position and -3 seconds per day in the crown right position, you can correct the rate via the regulator by e.g. +5 seconds per day. Then it has -4 and +2 seconds per day respectively in the two positions mentioned. Differences of the rate in different positions can be used purposefully to put down the watch over night so skillfully that a deviation accumulated over the day is partially compensated again!

How to regulate the Unitas / ETA 6497, we have seen above. These instructions work for all movements that have a normal regulator index, i.e. for the majority of all movements. Let’s take a look at the special features of some other movements.

Miyota 9015:

Unfortunately, since this movement has no regulator index, you have to regulate it directly on the regulator. So be careful!

Regulating the Miyota 9015

ETA 2824-2:

This movement has two peculiarities at once:

  • The automatic module hides the regulator.
    Only the balance spring stud is visible and therefore tempts the beginner to mistake it for the regulator.
  • Instead of a regulator index, the movement has an eccentric screw for fine regulation. However, there are also older ETA 2824-2 movements that have a normal regulator index.

The eccentric screw sits between a fork-shaped ‘regulator index’ which is moved to the left or right when the screw is turned. When the screw is in the position shown in the next picture, it is in the zero position, so to speak. If you turn it to the right or to the left, you can speed up or slow down the movement by up to 20 seconds per day. So the regulation range is about 40 seconds per day. Note that the slot of the screw is only open on one side!

Regulating an ETA 2824-2 (automatic module removed)

In the case of larger deviations, the automatic module must first be removed in order to access the regulator directly. If you know how to do this, it is actually quite simple. With large deviations, however, there is always the suspicion that the movement has acute need of revision! To check this, however, you need a timegrapher.

After unscrewing the rotor, only the two screws marked red in the next picture have to be loosened, then the automatic module can be removed as a whole. Since it is completely encapsulated, nothing will fall out.

ETA 2824-2: Removing the automatic module

Pocket watch movement with swan neck fine regulator:

High-quality pocket watch movements often have a swan-neck fine regulator, and it is also occasionally found on wristwatch movements. It consists of a spring that presses against the regulator index. On the opposite side, there is a screw, which can be used to move the regulator index. This allows the regulator index to be positioned extremely sensitively.

ARSA pocket watch movement with swan neck fine regulator

Just as an aside:
Chinese replicas of the Unitas/ETA 6497/6498 often have a swan neck fine regulation, which is unfortunately only a decorative element. The metal of the spring is so soft that it does not exert any pressure on the regulator index.

This article is not intended to be a compendium of all available regulating options, but an introduction to the subject for beginners. Those who are interested will find even more exciting technical solutions for regulating a movement!


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