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Thread: Seiko SKX Hack and Wind mod (7S26 replaced with NH36 or 4R36 movement)

  1. #1
    Master .olli.'s Avatar
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    Seiko SKX Hack and Wind mod (7S26 replaced with NH36 or 4R36 movement)

    I have been meaning to write about this interesting mod on my blog for a while. However having been rather short of time lately I keep deferring it… following a recent thread on the forum I thought I would post some info on here.

    The mod is applicable to SXK007 or SKX009 watches. It consists in the replacement of the original 7S26 movement with a “modern” Seiko Calibre 4R36 or Hattori NH36, which have a hack and wind facility.

    The thing to bear in mind is that there are two issues to get around with this mod:
    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. 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 SKX:


    Caseback open, revealing the 7S26 movement.


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


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


    After assembly gasket is cleaned and lubricated with silicon grease.


    A view of the SARB crown, I think it looks great on the SKX.



    This is how the movement performs out of the factory, not too bad at all (note in reality the amplitude is a little bit higher than displayed, as I have not set the timegrapher to the actual lift angle)



    It can be improved with some adjustment.


    And I finish with a pressure test.
    Last edited by .olli.; 16th September 2018 at 10:02.

  2. #2
    Grand Master
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    Interesting to see that the beat error's wrong prior to adjustment, typical of these movements!

    Where are the replacement crowns sourced?

  3. #3
    Master .olli.'s Avatar
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    Hi Paul
    I buy them on ebay, p/n 1E70D1SNS0. Supply can be an issue, sometimes they are just nowhere to be found!

    And yes as you said quite typical performance on these movements. I find that the variance between horizontal and vertical positions can also be improved usually with adjustment of the hairspring between the curb pins. The movement is fitted with an etachron type system so it makes things much easier!

  4. #4
    Grand Master
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    I`ve had one on the bench to play around with and I remember the etachron-style adjuster...........rather annoyed to find that my etachron key didn`t fit!

  5. #5
    Craftsman
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    Good write up thanks.

    I had this done to my SKX011 when after 20 years it required a service. The service option was not on the cards due to cost so I looked to replace the movement and the hacking option seemed sensible.

    It makes an excellent watch so much better.

  6. #6
    Master .olli.'s Avatar
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    Yes it is less labour intensive than a service, so the movement swap provides a good alternative, with a little improvement in functionality along the way...

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