About the Quartz watch Second hand alignment

 About the Quartz watch Second hand alignment

There are times when the second hand doesn’t quite hit the marker.（second hand mis-alignment）

I have received many questions regarding this from several customers asking why this was happening. I found an easy-to-understand explanation on the Citizen watch site, so I am posting a summary of it. 

The second hand’s movement is controlled by the gears. There is an intentional space placed in-between each gear.  That space(playfully) is called "backlash". This backlash is the cause of the second hand mis-alignment The gear space causes the place where the second hand stops to slip a little.

 An adequate backlash is essential for smooth gear operation. To put it quite simply, the gears would stop turning if the backlash was too small.

The reasons for the necessity of an adequate backlash are outlined below. 

１．Thermal expansion
The gears expand due to the heat from friction. A difference of just 10C can have an affect on gear alignment, even if they are small. The backlash is essential in minimizing that affect. 

2.　 Distortion
The gears of a watch take on pressure as they mov, causing these small parts to become slightly distorted. The backlash is necessary to minimize distortion.

 3.　Impact
Watches are sometimes dropped. The will cause the gears to break upon direct impact if there isn’t a bit of slack. 

 4.　Wear resistance
By creating a backlash, it is easier for lubricant to get up into the gears、preventing abrasion. 

5．Parts Standardization
The parts in a watch are not all exactly the same size, strictly due to error, despite an increase in machining accuracy.(Of course this is within the acceptable range for the maker).In order to account for this error, it is important to put the backlash into place to ensure that all parts turn smoothly..
（This might be the main reason.）

In conclusion

The Backlash is an essential part of the gear, and can’t be removed 100%.

While it is possible to reduce the backlash by improving the gear manufacturing precision and assembly method, doing so would have an impact on thermal expansion, impact, and wear resistance etc.

In other words, an adequate backlash is the solution for balancing durability, accuracy, and refined hand movement within the watch.

That is all of the available information from the Citizen watch site.

References:
Citizen watch site (Japanses)
https://citizen.jp/support/useful/lag01.html
Picture : Wikipedia
https://en.wikipedia.org/wiki/Backlash_(engineering)

The rest is what I have been able to determine speaking from personal experience.

SEIKO has come out with Backlash auto-adjust mechanism, which they use in the Grand Seiko Quartz for reducing second hand mis-alignment.

The Grand Seiko Quartz uses the power of the spring to reduce the slight second hand  mis-alignment that is created by the backlash as much as possible. (It’s like stopping the motion of a moving object with the power of a spring, which is difficult to wrap my head around.)

Even though the misalignment is far less noticeable in Grand Seiko is n comparison to any other watch, even the meticulously crafted Grand Seiko suffers from a slight second hand mis-alignment. (Sorry SEIKO)

About SEIKO Backlash auto-adjust mechanism,
https://www.grand-seiko.com/au-en/special/9f9s9stories/vol3/2/

Seiya Kobayashi