Mainspring Arbor Size - Seiko & Citizen Watch Forum Japanese Watch Reviews, Discussion & Trading
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Old 10-02-2019, 07:18 AM   #1 (permalink)
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Default Mainspring Arbor Size

Can anybody tell me if the lower mainspring arbor and port on a 7S26 is the same size as one used on a 6139B? Attempting to locate a jewel for a lower arbor port repair on a 6139B. Thanks.
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Old 10-02-2019, 08:09 AM   #2 (permalink)
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I just measured a 7s26b barrell, and the arbor pivots measure 0.97mm mainplate side, 1.47mm bridge side. Be aware that 7s26c has a mainplate jewel as standard and the pivot may be a different size.
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Old 10-02-2019, 09:56 PM   #3 (permalink)
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I just measured a 7s26b barrell, and the arbor pivots measure 0.97mm mainplate side, 1.47mm bridge side. Be aware that 7s26c has a mainplate jewel as standard and the pivot may be a different size.
Thanks for taking the time to measure pivots and provide me with this information. I checked the upper and lower arbors on a 6139B mainspring barrel. Pivots measure 0.97mm manipulate side and 1.47mm bridge side. Looks like they are the same. Again, I am looking at these measurements purely for jewel measurement purposes, not to say one barrel is interchangeable with the other.
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Old 10-02-2019, 11:07 PM   #4 (permalink)
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According to the web - 011123 is 2.4 x 1.5
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Old 10-03-2019, 12:03 AM   #5 (permalink)
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According to the web - 011123 is 2.4 x 1.5
Sorry, you lost me. Is this the OD and ID for the Seiko jewel part number used on 7S26? I am looking at a lower arbor jewel only to fit 6139B.
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Old 10-03-2019, 09:53 AM   #6 (permalink)
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From the forum "search" -https://www.thewatchsite.com/21-japanese-watch-discussion-forum/28800-6139-bizarre-jewel-count.html#/topics/28800?page=1
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Old 10-29-2019, 01:21 PM   #7 (permalink)
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From the forum "search" -https://www.thewatchsite.com/21-japanese-watch-discussion-forum/28800-6139-bizarre-jewel-count.html#/topics/28800?page=1
Hi, in that post you reference here Jewel #011123 is described as the "upper" or bridge arbor pivot jewel with an OD of 2.4mm and an ID of 1.5mm. The post also mentions Jewel #011142 as the "lower" or mainplate arbor pivot jewel but does not describe its dimensions. Any idea of the OD and ID of 011142? Thanks!
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Old 10-29-2019, 01:46 PM   #8 (permalink)
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I purchased a handful of lower mainspring arbor jewels for 7S26 hoping I could use them on my 6139 project. The jewel will fit the arbor on the 6139. The issue becomes finding a Seitz reamer the correct size necessary to machine the hole to fit the jewel to the main plate. The jewel seems to be an odd size. Using my digital calipers, I came up with these dimensions for the lower jewel for 7S26. Not sure if these are spec or not.

OD - 1.78mm
ID - 0.98mm
Thickness - 0.33mm
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Old 10-29-2019, 04:44 PM   #9 (permalink)
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Originally Posted by Vette Enthusiast View Post
I purchased a handful of lower mainspring arbor jewels for 7S26 hoping I could use them on my 6139 project. The jewel will fit the arbor on the 6139. The issue becomes finding a Seitz reamer the correct size necessary to machine the hole to fit the jewel to the main plate. The jewel seems to be an odd size. Using my digital calipers, I came up with these dimensions for the lower jewel for 7S26. Not sure if these are spec or not.

OD - 1.78mm
ID - 0.98mm
Thickness - 0.33mm
Interesting! Looking through the reamers in my Seitz kit I have 159 (1.59mm) and 179 (1.79mm)...I assume the former would be too small and the latter too large based on your measurement of the OD of that jewel.

On the other hand, since the rated accuracy of most digital calipers is +/- 0.03mm, if the true "spec" measurement of the jewel is more like 1.00mm (ID) and 1.80mm (OD) then the 179 reamer probably would work.

I'm also looking at generic Seitz center jewels and it looks like they make a 1.00mmX2.00mm and a 1.00mmX2.30mm. My Seitz set includes reamers that would work for both of those ODs (199 and 229), but the question becomes is there enough space or "meat" in the mainplate metal where the lower arbor pivot is located to allow reaming out to those larger sizes. That I don't know.

Where, may I ask, did you buy the 7S26 jewels you mention?

Thanks!
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Old 10-29-2019, 06:45 PM   #10 (permalink)
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Interesting! Looking through the reamers in my Seitz kit I have 159 (1.59mm) and 179 (1.79mm)...I assume the former would be too small and the latter too large based on your measurement of the OD of that jewel.

On the other hand, since the rated accuracy of most digital calipers is +/- 0.03mm, if the true "spec" measurement of the jewel is more like 1.00mm (ID) and 1.80mm (OD) then the 179 reamer probably would work.

I'm also looking at generic Seitz center jewels and it looks like they make a 1.00mmX2.00mm and a 1.00mmX2.30mm. My Seitz set includes reamers that would work for both of those ODs (199 and 229), but the question becomes is there enough space or "meat" in the mainplate metal where the lower arbor pivot is located to allow reaming out to those larger sizes. That I don't know.

Where, may I ask, did you buy the 7S26 jewels you mention?

Thanks!
I saw them for sale on ebay from a seller in Greece. I bought all 5 of the jewels. The ID of the jewels would work on the 6139 arbor. I ended up sourcing a set of jewels for the upper and lower from Adrian at VTA which required you to ream to 1.6mm for the lower. The thickness of the 7S26 jewel was only 0.33mm whereas Adrian's were 0.49mm thick. Not sure that makes a whole lot of difference though. I used my 159 reamer and it worked perfectly with the jewel from VTA. I was working on a customers watch so I did not want to risk trying to ream to 179 and trying the 7S26 jewel but there is enough meat in the plate to do that in my opinion. You should give it a go. Ream from the calendar side to the motion side so you get a straight shot at the hole with the reamer.
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Old 10-29-2019, 07:32 PM   #11 (permalink)
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I saw them for sale on ebay from a seller in Greece. I bought all 5 of the jewels. The ID of the jewels would work on the 6139 arbor. I ended up sourcing a set of jewels for the upper and lower from Adrian at VTA which required you to ream to 1.6mm for the lower. The thickness of the 7S26 jewel was only 0.33mm whereas Adrian's were 0.49mm thick. Not sure that makes a whole lot of difference though. I used my 159 reamer and it worked perfectly with the jewel from VTA. I was working on a customers watch so I did not want to risk trying to ream to 179 and trying the 7S26 jewel but there is enough meat in the plate to do that in my opinion. You should give it a go. Ream from the calendar side to the motion side so you get a straight shot at the hole with the reamer.
Good catch! I found an eBay source for the 011123 upper jewels at a reasonable price and just ordered a few, but can't for the life of me find the proper lower jewels...unfortunately it seems that Adrian at VTA isn't offering those sets any longer, at least I can't find them. He's got nothing at all for sale on the US eBay site, and doesn't list the jewel sets on his Australian eBay page. I even sent him a message through the VTA "Contact Us" link and got no response at all. I searched a bit further and found Walsh in the UK offers generic Seitz jewels in both 1.00X1.80 and 1.00X2.00...I think those are the best I'm going to be able to do. I did test-ream out the mainplate from a junk 6309 all the way out to 1.99mm (with the 199 reamer from the calendar side to the motion side as you say) and it looks ok to me, though I do think taking it out further than that would be problematic. I think I'll order a packet of both sizes from Walsh and see how they work. Thanks again for your responses and advice!

Mike
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Old 11-04-2019, 12:50 PM   #12 (permalink)
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Good catch! I found an eBay source for the 011123 upper jewels at a reasonable price and just ordered a few, but can't for the life of me find the proper lower jewels...unfortunately it seems that Adrian at VTA isn't offering those sets any longer, at least I can't find them. He's got nothing at all for sale on the US eBay site, and doesn't list the jewel sets on his Australian eBay page. I even sent him a message through the VTA "Contact Us" link and got no response at all. I searched a bit further and found Walsh in the UK offers generic Seitz jewels in both 1.00X1.80 and 1.00X2.00...I think those are the best I'm going to be able to do. I did test-ream out the mainplate from a junk 6309 all the way out to 1.99mm (with the 199 reamer from the calendar side to the motion side as you say) and it looks ok to me, though I do think taking it out further than that would be problematic. I think I'll order a packet of both sizes from Walsh and see how they work. Thanks again for your responses and advice!

Mike
So I did hear back from Adrian at VTA on his 6-series jewel sets...he's having more manufactured and hopes to have them back in stock by early December. Great news!

EDIT:

Adrian at VTA has his jewel sets back in stock as of late November 2019 and they are available on his eBay page.

Also, just to close the loop on my post above in case anyone else looking for information on arbor jewels comes across it: I ordered a few of the generic Seitz jewels I mentioned (in both sizes) and tried them two sacrificial 6309 mainplates, one reamed with the 179 reamer and the other with the 199 reamer. Both sizes of the jewels fit into the resulting holes just fine, but their full 1.00mm internal diameter appears from my testing to be too wide for the 6-series lower arbor pivot resulting in too much side shake when the bridge is installed. Adrian's lower arbor jewel, which only requires the mainplate to be reamed out to 159, is the far better option...in fact it's probably the ONLY workable option at this point unless you get extraordinarily lucky and find a stash of NOS genuine Seiko 011142 jewels for sale somewhere.

Mike

Last edited by IBNR; 12-05-2019 at 07:04 PM.
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