Seiko SKX NH36 movement upgrade


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The NH36 movement upgrade can be carried out on the SXK007 or SKX009 (7S26-0020) watches as detailed below. It consists of the replacement of the original 7S26 movement with a “modern” Hattori NH36 (or Seiko Calibre 4R36), which has a hack and wind facility.

Seiko 7S26 Hack and Wind mod

The NH36 movement upgrade is a cost effective alternative to a service, as it is less labour intensive than a full strip-down / clean and rebuild. It is also an opportunity to add functionalities to your SKX.

The thing to bear in mind is that there are two issues to get around with this upgrade:
1- The stem will be different on the new replacement movement, and the original SKX crown/ stem cannot be disassembled. To work around this, I use the crown and stem from a SARB059 watch, it is the perfect fit with the SKX and also looks great.
2- The day disc and date wheel in the replacement movement will be positioned for a watch with crown at 3 o’clock, so will not align with the aperture in the dial of the SKX which is at 4 o’clock. The easiest way to get around this is to remove the original day and date wheels from the 7S26 and fit them to the new movement.

I really like this mod, it makes for a perfect watch. I ended up carrying this out on my own watch. I tend to wear my watches in rotation, only for a day or so. Therefore the ability to give the SKX a wind before I start wearing it means I know I will get good timekeeping straight away, as I do not have to overcome the initial low state of wind.

Here are a couple of pics of the mod:

Starting with the caseback open, revealing the 7S26 movement.Seiko 7s26 NH36 upgrade


Movement out of the caseSeiko 7S26 4R36 upgrade


Dial, hands and date wheel/ day disc are off, ready to be swapped.
Seiko SKX007 movement upgrade


Hattori NH36 movement, will need to be fitted with the original day disc and date wheel and movement ring.
Hattori NH36 Seiko 4R36


After assembly gasket is cleaned and lubricated with silicon grease.


A view of the SARB059 crown, I think it looks great on the SKX.
Seiko SKX SARB059 Crown Stem


And I finish with a vacuum and pressure test, at -0.8 and 10BarG respectively to confirm water resistance.Seiko SKX pressure test

This mod features on my price list, please do not hesitate to contact me to book this in.