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Discussion Starter · #1 · (Edited)
I'm thinking of putting an NH35 movement in my Samurai so I can get it to hack and handwind. I like the look of the Sammie but the lack of handwinding in the movement is not so great. Would prefer for it to be "handwindable" for when I set the time after it stops.

Anyone know if the size of the 7S25 is similar to the NH35, and if the NH35 will fit in the Samurai case?

In terms of crown and date position the NH35 is good for the Sammie. Just wondering about fitting the movement in the case.

Thanks!
 

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Physically it's the same size, but the stem is different. Since the Samurai crown/stem is one piece you can't keep the original crown, and I don't know of any crown you could use to maintain the original look.
 

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Discussion Starter · #3 ·
Physically it's the same size, but the stem is different. Since the Samurai crown/stem is one piece you can't keep the original crown, and I don't know of any crown you could use to maintain the original look.
This is helpful, thanks. So either I find a crown that looks like the original or find a way to fit the original crown on the new stem, correct?
 

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Correct, but I think either ways are quite arduous tasks. Cousins UK has a good price on a 4R15 which doesn't handwind but has 50 hrs power reserve, which is an improvement anyway.
 

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Not sure what the Samurai crown/stem looks like but the below is a photo of a 7S26-0020 and NH35A crown and stem from my Dagaz diver - NH35A at the top

NH35 7S26 stems.jpg
 

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The 4th wheel pinion (for the second hand) is taller in a 4R movement (NH35). It is possible the movement won't fit due to the second hand making contact with the crystal.

Another consideration is stem clearance. I believe the movement is slightly taller, so the stem may rub against the inner tube due to the movement not lining up 100%.

You may want to consider a 6R15 instead. You would still need to source a different crown/stem assembly (4R stem is working in my 6R15). I think the stem clearance and pinion are the same as the 7S. Disclaimer: I could be wrong! Check! ;)


EDIT:

Check out this website.

http://www.timemodule.com/sii/index.php?route=information/technical_data

Both the NH36 and the NE15 are listed at 5.32mm.


I have swapped a 6R15 from a Sumo, to a Monster case and now in a SNZJ case with no issues. The Monster case had a 6R15 crown/stem assembly already. The SNZJ, I'm using a SSA051 (4R35) stem/crown.

I have a 007 with a 4R. No issues with pinion (domed crystal) or with stem/crown clearance. Also have a BFS with a 4R. Domed crystal installed. No issues with steam/crown.


Good luck! Once you get your hacking/hand-winding down, you can graduate to the next frustrating step of regulating the movement. :)
 

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Sometime Seiko uses different height 4th wheel, cannon pinion and hour wheel, hour depending on the case, e.g. on the SARG009, which even has a ticker dial. But I think the 7S25 and NH36 have the same height, as well the same overall thickness. I think the 6R is an hair ticker because of the additional auto bridge, but still fits.
 

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Discussion Starter · #8 ·
Here's what I got from searching online:

7S25 diameter 27mm, height 4.9mm

NH35 diameter 27.40mm (outside) / 29.36mm (casing), height 29.36mm

Looks close enough but not sure if case has enough clearance. Not also sure if I should consider the NH35 outside or casing diameter.

The important thing for me is really the handwinding function since I get annoyed with starting up the watch again after storage. Got used to watches with the feature already, hehe.
 

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5.32 is not equal to 4.9
As explained before. The hands carrying parts can vary depending on the casing. It is known that the 4R36/NH36 is straight swap for the 7S except for the stem, if you have trouble with this simple notion I can't help you further.
 

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As explained before. The hands carrying parts can vary depending on the casing. It is known that the 4R36/NH36 is straight swap for the 7S except for the stem, if you have trouble with this simple notion I can't help you further.
The heights of the two movements are different.
 

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The heights of the two movements are different.
No. The total height may be different depending on which hands carrying parts Seiko has used for different casing. Despite of that, people do 4R / 7S swaps all the time without issues.
The actual movement thickness is identical.

Now tell us again that their height is not the same and you will laureate a true genius.
 

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You may choose to think so.

Hey Pithy,

Can you PM me the technician link for the 7S? Couldn't find it online.

Thanks for confirming the height of the 7S. I was pretty sure it was taller - due to me having to use domed crystals in all of the 4R conversions I've done. Just wasn't sure how much taller exactly. I've swapped out 4th wheels on ETA's before - I suppose the OP could try swapping the pinion's. Seems like more work and could potentially involve wrecking the movement if you're not careful. Perfect scenario for a modder to dive in head first... ;)
 

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I was pretty sure it was taller - due to me having to use domed crystals in all of the 4R conversions I've done.
Plenty of conversions are done using non-domed SKX007 crystals and other cases, it fits fine.
Attached some tech sheets.
 

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Hey Pithy, Can you PM me the technician link for the 7S? Couldn't find it online. Thanks for confirming the height of the 7S. I was pretty sure it was taller - due to me having to use domed crystals in all of the 4R conversions I've done. Just wasn't sure how much taller exactly. I've swapped out 4th wheels on ETA's before - I suppose the OP could try swapping the pinion's. Seems like more work and could potentially involve wrecking the movement if you're not careful. Perfect scenario for a modder to dive in head first... ;)
PM sent.

No thanks necessary. Just trying to clear up as much as possible of the misinformation being spread on the boards.
 

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Plenty of conversions are done using non-domed SKX007 crystals and other cases, it fits fine.
Attached some tech sheets.
Thanks.

Yes, these sheets both confirm that the 4R is taller.

Some crystals are mounted closer to the dial face, and of course the thickness of Seiko crystals vary depending on the model.

There is definitely a difference between a 4R and 7S in height. I've experience first hand the second hand jam on the underside of the crystal after a straight swap. Crystal was a Dagaz domed on my TST 007. I've since swapped it out for a Double domed. I've had Seiko service tell me that they wouldn't put a 4R in a 7S case due to the 4th wheel and more specifically the crown/stem tube assembly issue.

I'd be interested to see which flat crystals work with a 4R in a 007.

This doesn't rule out that some cases may have more clearance between the dial and crystal to easily allow a 4R installation.
 
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