Seiko Tuna sbbn031 mods how to remove Crown/Stem & Bezel 7c46 Quartz
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Thread: Seiko Tuna sbbn031 mods how to remove Crown/Stem & Bezel 7c46 Quartz

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  1. #1
    Member Nanook65's Avatar
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    Seiko Tuna sbbn031 mods how to remove Crown/Stem & Bezel 7c46 Quartz

    I have a Seiko sbbn031 that I want to make some changes on. I searched for this, but didn't see anything specifically on the Quartz 7c46 Tuna so I apologize if this is redundant. I have taken the movement out of many of the different automatic movements from both Seiko and ETA/Sellita but never from this one. Here is what I am trying to do. 1) Change the crappy etched Crown for a older style engraved & Signed "S" Crown. 2) Swap the plain bezel insert to a Black fully lumed bezel insert, 3) Swap out the hardlex crystal to a Sapphire one& 4) Replace the Second hand with one that has the lume dot on the other end. I have done all of these to other Seikos like SKX & Turtle but this one is a bit different so:


    1) is there something to depress to disengage the crown stem? Is it the little depression/circle right below the "JA" Japan in my pic near the Crown? Does it matter if the Crown is in Hacked or unhacked position? I'm guessing that it does not, but better to check and be safe than sorry later.
    2) What about removing the bezel & bezel insert? Does it remove in the same way as skx or Turtle? Just pop it off with a case knife? I tried & it didn't want to budge. Is there a trick? I don't see a little indentation for the case knife idk...
    3) What about the Crystal? Once the Crown & Stem are out is there anything else I need to do? I don't see any tabs or any sort of holder in there, but maybe I am missing something



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  2. #2
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    Re: Seiko Tuna sbbn031 mods how to remove Crown/Stem & Bezel 7c46 Quartz

    I've got the same questions, and no answers.
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  3. #3
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    Re: Seiko Tuna sbbn031 mods how to remove Crown/Stem & Bezel 7c46 Quartz

    Let's bump this up. I have an Ashtray Tuna with the 7C46 and the crown tube threads need a clean up. I want to be very careful removing the stem and all. Been searching the interwebs for a couple days with no clear guidance.

    I got the stem out of a cheap Seiko quartz to remove the movement and clean some dust off of the dial, but seem to have mangled it and couldn't get the stem to engage properly on reassembly. I then got frustrated and did a "Hulk smash!" job of it and now have a lovely empty watch case to fill with tears of sorrow.
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  5. #4
    Member MediumRB's Avatar
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    OK, I figured it out. When the caseback is off and looking at the movement, there is a hole next to the "J" of "Japan" on the movement plate near where the stem is going in. Unscrew the crown and move it out and in to see the lever moving in the hole. With the crown back to the 0 position (i.e. turning doesn't change anything, but it is not screwing in, either), gently push inside that hole with a toothpick or tool and the stem should come out easily.
    When done fettling around, just be sure the movement is positioned correctly and then gently insert the stem and it will click and secure in the tube and movement when it is fully home.
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    Tick-tock in RoK GMT+9, no DST
    Notable Watches: Parmigiania Tonda 1950, Zenith El Primero Chronomaster, Piaget Upstream, Erwin Sattler Regulateur, Muhle Glashutte Seebataillon GMT, Eterna Madison Spherodrive, Vulcain Cricket 1951 Classic, Bell & Ross Space 3 GMT, Omega Constellation COSC (c. 1977), Bulova Accutron Astronaut (c. 1966), Sinn 556 Anniversary LE; Seiko: GS SBGT035, GS 5641-7000, 7C46-6009 "Ashtray Tuna", 6139-7069 "Blue Eye", 6139-6010 "Bruce Lee", 5740-8000 Lord Marvel 36'000, 6309-7040 "Turtle", 4006-7012 Bell-Matic, 6119-6400 UFO...

  6. #5
    Member Nanook65's Avatar
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    Re: Seiko Tuna sbbn031 mods how to remove Crown/Stem & Bezel 7c46 Quartz

    Quote Originally Posted by MediumRB View Post
    OK, I figured it out. When the caseback is off and looking at the movement, there is a hole next to the "J" of "Japan" on the movement plate near where the stem is going in. Unscrew the crown and move it out and in to see the lever moving in the hole. With the crown back to the 0 position (i.e. turning doesn't change anything, but it is not screwing in, either), gently push inside that hole with a toothpick or tool and the stem should come out easily.
    When done fettling around, just be sure the movement is positioned correctly and then gently insert the stem and it will click and secure in the tube and movement when it is fully home.
    Thanks!
    Question #1 is now answered.
    #2&3 remain...
    2) What about removing the bezel & bezel insert? Does it remove in the same way as skx or Turtle? Just pop it off with a case knife? I tried & it didn't want to budge. Is there a trick? I don't see a little indentation for the case knife idk...
    3) What about the Crystal? Once the Crown & Stem are out is there anything else I need to do? I don't see any tabs or any sort of holder in there, but maybe I am missing something

    I am not too worried about #3 as I figure I will probably figure it out, but I can NOT for the life of me get the bezel to budge. I am almost 100% certain that I should be able to slip a skinny knife in there and pry it, but the space between the bezel and the case is so narrow that even a skinny kitchen knife won't go in there.

    Anyone have a trick that works well?

  7. #6
    Member Nanook65's Avatar
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    Re: Seiko Tuna sbbn031 mods how to remove Crown/Stem & Bezel 7c46 Quartz

    ok, so now I have another reason to try and get this dang bezel off. I just got back from spending a week on the beach. I wore my Tuna on Rubber the entire time and I am loving this watch as much as any and much more than most. I didn't spend much time digging in the sand or anything, but when I returned home I noticed that the bezel doesn't work quite like it used to. I probably got a grain or two of sand in there and now I want to clean it out to return it to its former glory. I have tried and tried, but I can NOT for the life of me get this dang bezel to part from the watch case. my thinnest knife (a very thin kitchen knife) is still way to thick to get in between the bezel and the case. Does anyone have any tricks that they know of?


  8. #7
    Member Norm S's Avatar
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    Re: Seiko Tuna sbbn031 mods how to remove Crown/Stem & Bezel 7c46 Quartz

    sorry for digging up an old post, but where did you get the replacement crown with the engraved S?

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