Dr. Ito's thorough analysis of mechanical watches!! Vol.15 ~ Handling your watch ~ Crown operation

Good evening everyone!

This column talks about mechanical watches from an engineer's point of view. This is the 15th installment.

"How to handle your watch: Crown operation"

I will talk about this topic.

Almost all mechanical watches have a crown.

This is an essential part for operating a watch, including setting the time.

This time, I would like to talk about some trivia about how to operate this crown that may help you worry less about whether it is broken.

Winding the mainspring

Do you think that an automatic watch will keep working as long as you wear it? An automatic watch works by winding the mainspring with a built-in rotor that rotates with the movement of your arm. Therefore, if you take your watch off your arm often or don't move your arm much, it may not get enough power to run the watch, causing it to lose accuracy or even stop.

Therefore, you should wear it on your wrist for at least 8 to 10 hours a day.

If you often take your watch off your wrist or do little movement, such as at a desk, the driving force may be insufficient even if you wear it for long periods of time. To prevent this, it is recommended that you slowly wind the mainspring in the winding direction 10 to 20 times each morning before using it.

The mainspring of an automatic watch can be wound by turning the crown, just like a manual watch. However, because automatic watches are designed to wind the mainspring by winding the rotor, it is best to use the crown as an auxiliary winding tool.

If you are starting to use a watch that has completely stopped, rather than fully winding the mainspring by hand, it is better to wind it by hand 20 to 30 times and then use the rotor's power to wind it after that, as this will put less strain on the mechanism.

Winding the mainspring more than necessary can cause wear on the mainspring and parts of the automatic winding mechanism, so if you have an automatic watch, let the rotor power the winding.

Of course, the most important thing is to operate the crown slowly and carefully, so please be careful not to wind the mainspring in a hurry on busy mornings.

Fast forward the date

Mechanical watches have a "time period during which the calendar cannot be changed." The specific time period is generally between 8:00 PM and 4:00 AM . During this time period, the gears on the calendar plate and the gears that display the time are meshed, and the watch itself changes the date by its own power.
Therefore, please be careful not to try to change the date during this time period as it may result in the gears breaking and requiring repairs.

Here we will show you how to correct the date without making any mistakes.

①Pull out the crown all the way.

②Advance the hands so that they indicate around 6 o'clock.
(This is the safest needle position.)

③ Turn the crown back one notch and set it to the day before you want to adjust the calendar.
(If you set it to the 6th, it will be set to the 5th.)

④ Pull the crown out again to the end and advance the hands clockwise.
Check that the date changes when the hands pass midnight.
(The time when the time changed is midnight.)

⑤After confirming that the date has changed, move the hands clockwise.
Set to the current time.

⑥After setting the date and time, return the crown to the winding position.
For models with screw-down crowns, screw them down securely.

With the exception of some models, most mechanical watches require manual calendar adjustment on the day after the end of February, April, June, September, and November (short months).

Time setting

The speed at which a clock advances or slows is called "accuracy," and the term "daily difference" is used to describe how many seconds the difference is per day.
The accuracy of a typical mechanical watch is expected to be around -10 to +20 seconds per day .
For vintage watches, the acceptable range is -30 to +60 seconds per day .

A daily deviation of 10 to 30 seconds is not considered a malfunction and is within the acceptable range for a mechanical watch.

In addition, the mechanism is also affected by differences in posture (when worn on the wrist, it can be in different positions), temperature, and how wound it is, so if used for a long time, this tolerance range may be exceeded.

We also sometimes receive complaints about problems such as, "Even though I set the time to exactly the right time, it immediately becomes about one minute slow."

This happens due to a mechanism called backlash.

Backlash is the gap between gears.
For the two driving gears to mesh properly, there must be a certain amount of clearance, otherwise the teeth will press tightly together, causing wear and excessive force.
Additionally, problems may occur such as the rotation not being smooth, or, when thermal expansion is taken into account, the mechanism may stop moving altogether.

This backlash is unique to watches, which are precision instruments, but as a side effect, it creates gaps that cause the hands to become misaligned when adjusting the time.

This is more noticeable in quartz watches than in mechanical watches, but even mechanical watches can be off by nearly a minute depending on the model.

Some degree of misalignment is believed to be caused by this backlash, and most manufacturers consider it to be within the acceptable range, so there is no need to worry too much about it.

In order to reduce the delay in the start-up of the hands caused by this backlash, when setting the time, it is effective to "turn the hands backwards" as the final step to set the watch to the desired time.

By rotating the hands in the opposite direction, the delay in the hands starting to move due to backlash is eliminated, and the problem of the minute hand starting to move about one minute late even though it has been set perfectly in time with a time signal is eliminated.

summary

What did you think?

Even the crown that you operate every day without even thinking about it can help keep your beloved watch in good condition if you understand its internal structure and handle it with care.

We hope that this article has been useful to you and has piqued your interest in luxury watches! If you have any questions, please feel free to contact us directly and we will answer them thoroughly. We look forward to your visit and inquiries.

Look forward to the next one! See you next time!