Servicing a mechanical watch: when it is due and what it involves

One morning you notice it: the watch that ran reliably for years is suddenly half a minute fast. Or it has stopped after a night on the bedside table, although it used to keep going into the next day. A mechanical watch rarely makes a fuss. If you can read its quiet signals, you have it serviced in good time and avoid care turning into repair.

The signs: when your watch belongs in the workshop

In a mechanical movement, wheels, pinions and bearings mesh continuously. Fine oils reduce friction but lose their effect over time. These signs suggest it is time to see a watchmaker:

• Rate deviation: the watch deviates noticeably more than usual or varies from day to day.
• Power reserve: once taken off, the watch stops sooner than before, even though it was fully wound.
• Winding and operation: the crown feels rough or scratchy, the date changes untidily, chronograph hands do not return exactly to zero.
• Moisture: condensation under the crystal is an emergency, as water that has got in can corrode parts. The watch should go to the workshop immediately.
• Impact: after a fall, a check is worthwhile, even if the watch keeps running.

Not every sudden deviation means wear. If a watch suddenly gains a lot of time from one day to the next, magnetism may also be the cause. More on this below.

Intervals: what manufacturers recommend

There is no single interval that applies to all watches. The published recommendations of major manufacturers range from a check roughly every three years to a complete service every five to eight years. Some manufacturers also advise having the water resistance tested every year. How much leeway you have depends on your wearing habits, sport, climate and the age of the watch. The figure that counts is the one given in the documentation for your model.

Besides the calendar, the watch itself is the best indicator. If you measure the rate regularly and know the power reserve, you will notice changes early. If you only react when the watch stops, you risk spent oils having already worn the bearings and wheels.

What a service involves

A complete service is more than an oil change. One manufacturer describes the process in eight steps that are common, in this or a similar form, in many workshops:

• Remove the strap or bracelet, open the case, take out the movement.
• Dismantle the movement completely and clean every part in an ultrasonic bath.
• Replace worn parts with original parts.
• Reassemble the movement and oil the contact points.
• Regulate the rate and check the movement’s functional values.
• Clean and refinish the case and metal bracelet.
• Assemble the case and renew all the gaskets that ensure water resistance.
• Finally, check function and appearance.

Be careful with refinishing: polishing removes material and can alter edges. If the original condition matters to you, exclude it explicitly. Before handing the watch in, also clarify:

• a written estimate covering all planned work,
• whether replaced parts are original parts and whether you get the old parts back,
• what warranty or guarantee the workshop gives on its work,
• whether the water resistance is tested and documented after the case is closed.

Keep receipts and service records, because they count when you sell later on, as the article on authenticating pre-owned watches shows.

Water resistance: ISO 22810 and ISO 6425

Water resistance is not a permanent state but a property ensured by gaskets, and gaskets age. Every time the case is opened, even for a battery change, a new test is required. The standard ISO 22810 sets out the requirements a watch described as water-resistant must meet and how this is tested, including condensation and overpressure tests. The figure in bar or metres describes a test pressure under laboratory conditions, not an approved diving depth. It does not reflect movement in the water or aged gaskets.

For divers’ watches, the stricter ISO 6425 applies. It covers watches designed for dives to a depth of at least 100 metres that have a secured device, legible in the dark, for displaying the dive time. In its pressure test, the test pressure is 25% above the stated value. For all watches: screw down screw-in crowns before contact with water, and only operate the crown and pushers underwater if the manufacturer expressly permits it.

Between two services: magnetism and storage

Magnets are everywhere in daily life: in smartphones and tablet cases, bag clasps, power adapters, loudspeakers and induction hobs. If a mechanical watch comes too close to a strong field, the balance hairspring can become magnetised. The watch then runs markedly fast or slow, or stops. The standard ISO 764 tests magnetic-resistant watches with a field of 4,800 amperes per metre, equivalent to around 60 gauss. For comparison: the COSC ‘Excellence Chronometer’ level tests at 200 gauss, the METAS certification at 15,000 gauss.

A magnetised watch generally does not need a service: the watchmaker demagnetises it and checks the rate. Keeping a few centimetres away from magnets helps prevent it.

Store watches dry, protected from dust and individually, so that they do not scratch one another. Leather straps need air; more on this in the article on leather quality. If an automatic watch has stopped, wind it with a few turns of the crown before wearing it. Instruction manuals often advise against changing the date between about 9 pm and 1 am, because the date mechanism is at work during this time.

A watch winder keeps automatic watches running. This is especially convenient for calendar complications, which are laborious to reset. But bear in mind: every hour in the winder is running time for wheels, bearings and oils. A winder is therefore more a matter of convenience than a care measure. If you use one, set the direction of rotation and the number of turns according to the specifications for the movement in question.

Measure the rate for a week straight after the service and note the average. This is your personal reference value. If the watch later deviates markedly from it, or the power reserve drops noticeably, you know the next appointment is approaching.

The takeaway: a service follows not only the calendar but the condition of the watch, and you recognise that best when you know your figures. Record the deviation in the Accuracy Calculator. And if you spread the cost of servicing across the days you wear the watch, the Cost per Wear calculator shows what care really costs.

Accuracy CalculatorMeasure your watch and compare it with COSC and METAS. Cost per WearWhat a piece really costs each time you wear it, compared side by side.