Seiko Nh36 Walkthrough

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Seiko NH36 Walkthrough
This walkthrough complements the 7S26/7S36 excellent walkthrough on this site by Lawson ( I strongly recommend to check out Lawson's walkthrough first).
This is a more recent movement based on the said 7S26. It is a 24 jewels day/date,  center seconds, movement with hacking capabilities and manual wind. The ligne is like its predecessors ~12. It is popular in the new Seiko models and Invicta watches among others.
In brief, former movements didn't have hack or manual wind. Still, several parts are interchangeable with the older 7Sxx series. Here is the service data: 6810_Seiko NH3 Series Part Sheet.pdf
My first step here will be to remove the "oscillating weight"  and balance and place in a safe place. Those parts could be easily damaged so we put them out of harm's way.
Starting on the bottom side, normal removal of "snap for day star with dial ring"
Note that the reverse of the snap has indentations to fit a small screwdriver and lift it clear of the day disc (yellow arrow). This is standard for this movement family and snaps, day disc and date rings are interchangeable. The other picture shows the snap right side up.
Under the day disc:
Showing the "intermediate wheel for date corrector":
Moving on, "date indicator maintaining plate" and related screws. No philips proprietary 4th screw here, all four are the same...
Date jumper and date dial:
also "Day Date corrector wheel", "hour wheel", "minute wheel and pinion", "date indicator driving wheel" and "intermediate date driving wheel and pinion":
"Canon pinion" and the new addition for this movement "Day Date corrector setting transmission wheel E":
Removing the "Dial holding spacer" (this one is from a 7S26 not the original one which is thicker):
Turn over Baby! Ehem, just the other side view... :)
More changes are introduced:
We remove the "automatic train bridge" and screws:
Notice the added 24th jewel (red arrow) to accommodate the newly designed "second reduction wheel and pinion" (blue arrow) which is much thinner than in previous movements.
Removing "ratchet wheel" and its screw (nothing new here):
Removing the familiar "Barrel and train wheel bridge with hole jewel frame", notice the familiar "long screws" inherited from previous designs:


This bridge has been modified also to add the manual winding mechanism. More on that later.
Removing the click and the "fourth wheel and pinion":

post-253-0-50488100-1424971637_thumb.jpgAt this point we remove the rest of the loose bits ("Third wheel and pinion", "scape wheel and pinion" and "barrel complete with mainspring":
Then we remove the "Yoke spring" and characteristic "long" screws (different from the ones used in the balance cock and "barrel and train...bridge":
Removing the "yoke" and the "setting lever", note how the lever shape has changed from the previous models:
The story so far after removing the "center wheel bridge" and its short screws, the "center wheel and pinion", "pallet bridge" and "pallet fork":
On the main plate, showing the added "balance stop lever":
And the "day-date corrector setting transmission wheel A" (red arrow), "winding pinion" (orange arrow) and "clutch wheel" (blue arrow):
Close up of what is left on this end:
Removing the "guard for day-date corrector setting transmission wheel" and short screws. Underneath the "day-date corrector setting transmission wheel C" and the "Day-date corrector setting transmission Wheel B":
After removing the transmission wheels B and C we are left with the built in wheel on the frame:
Notice that transmission wheel "B" (blue arrow) is thinner than its counterpart "C":
"Barrel and train wheel bridge with hole jewel frame" disassembly:

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Thank you Geo, I got those as inspiration. I'm not through yet with the strip tease..errr...strip down of the movement. Then, it will be the reassembly, notes and so on. Hope it help others that wish/have to tackle this critter! :)





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Great Walkthrough bob. It's not the easiest of watches either - lots of unconventional looking parts.

I know this is really going to help people :)

Sent from my iPhone using Tapatalk

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Most excellent Bob!  You my friend are "Mr Seiko" on this forum, without a doubt.


Loved the layout, and especially liked the coloured indicators to parts you are discussing ... this will benefit a lot of new comers, and help give them the confidence they need to tackle this movement.


Keep'em coming brother!!

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Thank you Lawson and jnash, appreciated!


So continuing  "Barrel and train wheel bridge with hole jewel frame" dissasembly.

These are views right side up and upside down respectively:

post-253-0-03157500-1425101770.jpg post-253-0-84153300-1425101775_thumb.jpg

Removing the "reduction wheel holder", "pawl lever" and "first reduction wheel " shown left to right:


Then, on the other side removing the "lower plate for barrel and train bridge" and srew:


Finally, removing the "ratchet sliding wheel spring":


Note that in page 12 of the Service data in pdf -- attached at the beginning of the walkthrough -- lists the recommended procedure for removing/reassembling the "reduction wheel holder" and the "ratchet sliding wheel spring".

So reassembling of this bridge should be done in reverse and following the recommendations in this page:



This ends the disassembly of the NH36 movement.

Reassembly following next.

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Listen here Bob! ... all these great pics and detailed explanations are going to have to stop!

What?!   Do you want the average man on the street to gain the knowledge, and confidence, to service his own watch ?!@#! :blink:


This must end now, and this thread should be removed!  I'll be writing to the admin of this forum to explain that watchmakers are a magical elect group, like ninjas :ph34r:  :ph34r:,  and our secrets must not be relieved!!

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On a serious note, that really is a well put together walkthrough. I really should take note and put more effort into it myself.


Agreed Geo, this forum is becoming a wealth of good information on a large variety of movements.

Looking forward to the upcoming assembly posts Bob.

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Thank you guys, I appreciate your kind words. No worry Lawson, lots of secrets still uncovered! :)


BTW, my camera is a canon powershot elph 520 in auto! I'd love to have better quality pictures and/or more detailed but there is not much I can do with a probably limited equipment...if I had the knowledge of how to use it!


Please, chip in for completeness/suggestions if you see I've missed something or anything could be disassembled/assembled further/better! I'd love the input!





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So, here comes the assembly of this movement. It should be short for two reasons:


1.- I got so much into it, I forgot to take more pictures.

2.- It is mostly a reverse of the disassembly and/or covered in Lawson walkthrough where similarities match.


All that said, I usually start at the keyless works with this movements:


Remember the skinnier cog goes towards the crown. One trick to hold this bunch of parts without falling is to use rodico to cover the bottom of the hole.


post-253-0-31632900-1427899004_thumb.jpg post-253-0-74801100-1427899005_thumb.jpg


Then, I hold them with the stem:


NOTE: The arrow points to the "groove" where the balance stop lever and the setting lever engage.




Turn the movement on the holder and do the other part, the manual winding portion, again the skinny cog goes on top of the stem:


post-253-0-22350800-1427899010.jpg post-253-0-87484500-1427899008.jpg


Center wheel and its bridge, just like the old 7S26 movement:


post-253-0-68765300-1427899011_thumb.jpg post-253-0-18000300-1427899013_thumb.jpg


And proceeding as per the old movement: 






Escape wheel in place:




Pallet fork and bridge followed by the Barrel and train wheel bridge (after quickly putting it together):




At this point I think it is a good idea to stop this side, turn over and first add the dial holding spacer:




Then the canon pinion:




Finally all the other parts (forgot to take all the intermediate pictures), up to the date jumper:




Then add the date dial and on top the date indicator plate, At this point a present 2 screws to hold it down loosely (not tighten) and check that the date jumper can do its job. and its wheel is engaging properly.




Finishing the dial side:




Then turning over and adding the balance:




And to finish we add the oscillating weight with ball bearing....standard procedure on this movement....




One important part here is to match the center of the oscillating weight and winding stem and set the hole of first reduction wheel gear on the imaginary line toward the balance bridge guide pin. As per service data.


So, there you have it! NH36 complete walkthrough!







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