Have you ever wondered how Seiko automatic watches work and what secrets they hide in their cases? In this article you will learn what mechanisms move the hands of automatic watches and what provides precise time measurement.

Types of movements in Seiko watches

The Seiko brand offers a wide range of automatic watches. Of course, apart from automatic watches, you can also find some quartz and solar timepieces as well. Although both quartz and solar movements are true technological innovations, in today's article we're going to focus only on automatic movements.

Seiko automatic watches feature several calibres. The calibre 4S15 (originally 5246) is often used in chronographs and certified King Seiko watches. This movement is valued for its high frequency, which is 28,800 vph, and for its hand-winding mechanism.

The evolution of Seiko caliber 7S26

Since 2011, the boom for Seiko 4R movements has continued. It concerned mainly calibres 4R36 that originated from calibres 6R15 (6R15 calibres were used in the SARB series). Both the former movements and the later 4R calibres feature a hack seconds function and hand-winding mechanism. This means that these watches guarantee precise time setting and manual winding. The automatic movement 6R15 comes with a mainspring Spron 510 (a metal which is distinguished by its excellent flexibility, high durability and resistance to corrosion and heat). It can be used, among others, in the manufacture of medical instruments, or springs for mechanical watches. Once the spring is fully wound, the calibre boasts a power reserve of over 50 hours. The calibre 6R15, on the other hand, originated from the famous and reliable calibre 7S26. In other words, 4R is the most modern, redesigned version of the calibre 7S26. It also features a decorative rotor, as opposed to the 7S series.

The table shows the development of further improved movements of Seiko watches:

The first models that used the popular 4R calibre (mainly 4R15 and 4R16) were those from the Seiko SRP series (the first such watch was Seiko SRP001), which in the late 1990s were also referred to as Superior watches as they were distuinguisged by more advanced operation than Seiko 5S.

Exceptional ETACHRON

The biggest change, however, was the use of the ETACHRON regulating system in, for example, the 7S26B model. Its function was to provide accurate timekeeping and better performance of the watch. The time measurement deviation of this model was only +2 seconds per day. This regulator had many advantages, but there was one problem. If the watch was subjected to any kind of shock, it’d accelerate considerably or stop completely. The fault lied in a hairspring (part of the balance), which jumped out of the regulator. Over time, this defect has been fixed. The models from the 4R and 7SC series function correctly.

Types of 4R calibre and their specifications

Currently, the basic Seiko 5 and Seiko 5 Sports models come with a very precise calibre 7S26C. Some Seiko 5 Sports watches feature an equally good movement 4R36A.

In the 4R series the following models are distinguished. Their frequency of the balance is 21,600 vph.

Precision of Seiko watches

This article is a brief description and an attempt to classify the automatic calibres used by Seiko. The company focuses primarily on quality and precise timekeeping of its products. At the same time, the brand doesn't forget about the atrractive design - Seiko watches feature a very elegant case that catches the eye with its stunning look.

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