Understanding Watch Movements: 7S26 vs NH35 for Seiko Modding

Watch enthusiasts who are venturing into the realm of Seiko modding often grapple with a crucial decision: choosing the right movement. Two of the most popular movements that come up in any Seiko modding conversation are the Seiko 7S26 and the NH35 both possessing their unique characteristics and advantages. This article aims to clarify their differences and help you make an informed choice for your modding project.

The Seiko 7S26 Movement

Introduced in 1996, the 7S26 is a veteran in Seiko’s range of automatic watch movements. Found in some of the most well-loved Seiko models like the Seiko 5 series and the SKX dive watches, the 7S26 is an automatic, non-hacking, and non-hand-winding movement. Its robustness and reliability have been proven over the decades.

The 7S26 operates at a frequency of 21,600 vibrations per hour (vph), offering a smooth six ticks per second sweep of the second hand. Its power reserve is approximately 43 hours. However, the absence of hacking (the ability to stop the seconds hand) and hand-winding functionality may be a disadvantage for some modders and watch aficionados who prefer more control over their timepiece.

The 7S26 movement comes pre-installed in the SKX007, many wish it had hand-winding and hacking. The NH35 NH36 NH38 which have these features are a desirable mod on the SKX007 watches. The 7S26 movement also comes with a black movement holder which is thicker than the NH movement’s grey movement holder. This difference in thickness of movement holder has a bearing on the choice of case back you use on your watch.

The NH35 Movement

The Seiko NH35, also known as the 4R35 in some Seiko branded watches, is a step up in terms of features. Like the 7S26, it is automatic but adds hacking and hand-winding capabilities, providing added flexibility for the wearer.

This movement operates at the same 21,600 vph as the 7S26, ensuring a similarly smooth sweep. It also boasts an improved power reserve of about 41 hours. For modders who want a more feature-rich base for their custom watch, the NH35 is an appealing choice.

Because the NH movements uses the thinner grey movement holder, if you wish to use the same/original case back on your watch you need to swap the black movement holder on the 7S26/4R35 onto your NH movement. If the original case back is accompanied with the grey movement holder, the whole movement will sit ‘hollow’ in the watch case even with the case back fully tightened.

If you decide to also change the case back and use it with a grey movement holder, you should go for a case back that has slightly longer thread (Our case back CT231, CT273, CT239B for example)

7S26 vs NH35: Which One for Your Seiko Modding?

When choosing between the 7S26 and NH35 for your Seiko modding project, the decision ultimately boils down to personal preference. If you value a tried and tested workhorse movement with a history and do not mind the lack of hacking and hand-winding, the 7S26 is a classic choice. On the other hand, if you desire those additional features and don’t mind paying a slightly higher cost, the NH35 is an excellent option.

Whichever movement you choose for your Seiko modding journey, both the 7S26 and NH35 carry the quality and reliability that Seiko movements are renowned for. They serve as excellent foundations upon which to create your unique timepiece.