Seiko 5 Build Questions
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  1. #1
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    Seiko 5 Build Questions

    All,

    I have a case from an old Seiko 5 7s26-8760, and I want to build a low-cost watch for fun. Iíve never built a watch with an old case before, so I have a few questions for yíall.

    1. Where can I get a good used 7s26 movement? They cost $35 on eBay, and thatís too much. I donít want to kill a perfectly good watch for this project, so Iíd prefer a homeless used movement in good condition.

    2. Where can I get a tall acrylic crystal for this watch?

    3. The caseback gasket seems glued to the caseback. Is this accurate, or is it just smashed in there?

    4. Any other advice for me before trying to build a watch in an old case?










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    SKX009J / SKX007K / SKX171 / Marathon T-SAR / G-Shock 7900B

  2. #2
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    Re: Seiko 5 Build Questions

    Cool Project, I hope you succeed.

    4) See if you can find the model number on the case, it might be possible to use that as a reference to locate the corresponding part numbers for parts like crystals, crowns, gaskets in Seiko catalogues Have you found the right crown for that case?

    1) You might find a used movement for sale on this forum, perhaps from someone who's done a movement swap. That said, $35 is a good price, and you could as well get a new NH36A from the same seller and have an upgraded movement altogether. That's the route I went with.

    2) You could try Spencer Klein https://www.kleinvintagewatchrepair.com/ . If he doesn't have something suitable, he might be able to suggest what you need specs wise and where you should look. I've also seen acrylic crystals on ebay.

    3) Probably smashed?

  3. #3
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    Re: Seiko 5 Build Questions

    8760 is of course the model number.

    Inspect that gasket and if it's not torn, clean and apply silicone grease to it and reuse. Maybe tighten the caseback just a little more. (That being said, t's probably shared with lots of other models.)

    Use a vernier caliper to measure what the crystal size needs to be. I suspect that dimension will again, be shared among many Seikos.


    I have no idea why "the world's biggest watch site" doesn't actively attract modders selling spare parts, but it just doesn't. We're more of a "hey, look at my new toy" website unfortunately.
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  5. #4
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    Re: Seiko 5 Build Questions

    Thanks for all the help folks. Here is what I found and a follow up question.

    1. The stock crystal according to Jules Borel is 310W17L50C. I found one on the bay.

    2. I also found a serviced used 7s26 for $35 on the bay.

    3. The caseback gasket came off with some work, and it seems to be the same diameter as the 7s26-0020 gaskets I already had. Iím going to give it a shot.

    4. The crystal gasket is G283-124. I canít find it anywhere for sale, but Iím looking.

    5. Question: I still need a stem. Can I use a SNK809 stem and crown for this project? Itís the same movement, but Iím not sure if itís compatible with the case.





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    SKX009J / SKX007K / SKX171 / Marathon T-SAR / G-Shock 7900B

  6. #5
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    Re: Seiko 5 Build Questions

    You should be able to get away with the stem provided it's a new untrimmed item, you can fit that easily, but I can't comment with certainty on if the crown will work (I have no clue). You could always offer up the crown to the case and see if it fits .

    Someone could try measuring the crown and crown tube dimensions for an SNK809 using a micrometer, and then you can check them against your case perhaps.

  7. #6
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    Re: Seiko 5 Build Questions

    It turns out the crystal I got on the bay was not the correct fit.





    The inside diameter of the case measures 30.2mm for me. I have the part number from Jules Borel (310W17L50C or CRY-3954G), but neither JB nor Ofrei have the part.

    Any other ideas?


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    SKX009J / SKX007K / SKX171 / Marathon T-SAR / G-Shock 7900B

  8. #7
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    Re: Seiko 5 Build Questions

    30.0mm x 1.5 (or 1.6mm thick) crystal will work.
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  9. #8
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    Re: Seiko 5 Build Questions

    Ouch! Try a 30mm crystal as suggested above.

  10. #9
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    Re: Seiko 5 Build Questions

    Final report

    1. It turns out the crystal was 30.2 x 1.7. After trial and error, I found a generic crystal through Jules Borel and the parts database on the JB website. The mystery was solved when the bezel that I didnít think could come off popped off while I was trying to press the new crystal into place. I set the crystal, popped the bezel back on, and it fit perfectly.

    2. I had to buy a new corn and stem, trim the stem to the exact length, and then seal it with Locktite Blue. An SNK809 crown/stem was too long as was (obviously) the SKX007 crown/stems I already had. Too much stem, and the crown sticks out. Too little, and the stem wonít click into the proper movement position, and it falls out of the case. Both the crown and stem came from JB.

    3. The narrow 7s26 dial holding spacer that came with the movement was a perfect fit for the case.

    4. I bought a cheap ultrasonic cleaner for the case, and it worked wonders.

    5. I like how the Dagaz Magneto handset works with the SNK dial I had.

    6. The refurbished 7s26A movement is running +28 seconds fast so far on its first day.

    7. I bought parts from Otto after, Esslinger, and JB. Each delivered in under 3 days. I much prefer doing business with these folks than the bay if it can be helped because they work so quickly, and there is no wait time for US Customs

    8. Thanks for all the advice.





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    SKX009J / SKX007K / SKX171 / Marathon T-SAR / G-Shock 7900B

  11. #10
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    Re: Seiko 5 Build Questions

    Congrats!

    The result is beautiful. The combination of that 70s style case, with my favourite snk dial with the black strap is fantastic. It makes it look like an instrument.
    Would you consider swapping the day and date discs to black ones?

    I'm seriously considering finding that same case and building a watch around it now lol.

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