Seiko 7A38 - by the numbers

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Forum Home > Parts Info, Tech Tips and Tinkering > Different Methods of Bracelet / Strap Attachment

Seiko7A38
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Conventional wisdom (at least, to the less-well-informed, it seems) would have you believe that the bracelets on all 7Axx’s are attached by spring bars. I had to chuckle to myself about something (well-meaning, but completely wrong) which Thian wrote in response to a post about a 7A38-6020 on SCWF last year: http://www.thewatchsite.com/index.php/topic,25719.msg150194.html#msg150194

Thian had by then partially post-edited his original reply to cover up his mistake, as one would, naturally. ;)


Indeed, most ‘conventional’ 7Axx’s did use double-ended spring bars of either 1.5mm or 1.8mm diameter.

I can’t speak with authority, about other 7As without actually checking on Seiko’s database, but for the 7A38’s it’s:

10mm on the 7A38-6080; 7A38-702x; 7A38-7030; 14mm on the 7A38-6090; 16mm (on the slightly odd-ball 7A34-701x) ....

and 18mm or 20mm on the rest.

 

However there is another sub-genre of 7Axx which uses a different method of bracelet attachment, which I call ‘Pin and Tube’.

This group includes the: 7A38-6020, 7A38-6109, 7A38-704x family and related JDM 7A38-7110, the 7A38-705x’s and 7A38-714x’s.

Off the top of my head, it’s also used on the 7A28-7070; 7A28-7110 (which use the same lower case design as the 7A38-705x) and the slightly quirky-looking 7A48-701x.

This alternative system used for attaching the watch case to the bracelet, is best described as being very closely akin to the bracelet pins used to add and remove adjustment links from Seiko’s latter-day divers, the Knights, Samurais and Monsters.   

 

This PMWF article explains the system: http://www.pmwf.com/Watches/WatchTools/BraceletSizingTools/AFBraceletSizingToolUse.htm

In that article they refer to them as ‘Pin and Collar’; I’ve already called it ‘Pin and Tube’, but on Seiko’s database, the relevant parts are referred to as: Bracelet Fixing Pin and Bracelet Fixing Pipe.

Here's the bracelet to watch case 'Pin and Pipe' used on the 7A38-6020, as documented on Seiko's database, as an example:




 

Note: these are the parts for this particular case model - different lengths and diameters are used on other 7A's besides these p/n's.


I haven't taken any special photos to specifically illustrate this article, so you'll just have to squint hard at these. 

A couple of a 7A38-6020 (first one, courtesey of Derek):





 Here's a lucky shot I took of my 7A38-7050, which shows the (push) end of one pin reasonably well:




You may also encounter these pin and tube fixings, not exposed on the ends of bracelets, but also hidden deep inside drilled lugs - such as found on the 7A38-6109:




Indeed, as Simon knows well, you'll also find them, mostly used in conjuction with drilled lugs on a number of Seiko 7T32 models. ;)


Now, if you read that PMWF article, it may give the impression that you can push these pins out with the other end of a spring bar tool.

That is presuming you can see down the hole in the drilled lug, and are actually pushing the pin out in the correct direction, of course.

In reality, the collars / pipes are often choked up with gunge, and sometimes the pins are tight, or corroded into their fixing tubes.

Because of the diameter of the watch head - anything around 40mm, say compared to the maximum 24mm width of a bracelet ....

it isn't always possible to use a normal (typical cheap ex-eBay) bracelet pin pusher on these bracelet to watch head fixing pins. 

Then there really is only one solution - the 'proper' tool for the job - one of these:




February 23, 2012 at 1:48 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

There is a similar, but subtly different method of 'pin and tube' strap fixing used on the Yema Spationaute III and N8 Flygraf models.

These also have drilled lugs:




It's probably best demonstrated by this photo, of a watch head only, which I've borrowed from Forumamontres:




What you're looking at in the second photo, although it may not immediately be obvious, is a 1.8mm O.D. x 1.4mm I.D. tube which fits across the 22mm lug width. Through it (via the holes in the drilled lugs) is pushed a 1.4mm Ø pin - approx 25mm long. Not only is the pin a very tight (almost 'interference') fit, but both pin and tube are cinched at mid length - as shown in this diagramatic illustration borrowed from Cousins website:


The photo against their part number B33492G is actually clearer:



Needless to say these things are murder to push out, much tighter than the Seiko 'Pin and Collar' system - and obviously something of a mystery to certain alleged jewelers and watchmakers. One of the 'reduced' 38mm Yema Spationaute III's I bought (these are 20mm lug width, but use pins and tubes of the same diameter) came fitted with a non-original strap, and on very sloppy fitting double-ended spring bars. No sign of the original pin and tube fixings - long since gone. On the inside of one of the lugs was clear evidence of what had become of them  - jeweler's hacksaw marks !! 


In my opinion, there is only one proper way to get the strap pins out of a Yema Spationaute III or N8 Flygraf - the Seiko S-926 tool.

February 23, 2012 at 3:23 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

More on the 'Pin and Collar' (or Pipe / Tube - whatever you want to call it) method of 7Axx bracelet attachment, in a thread on SCWF:

http://www.thewatchsite.com/index.php/topic,968.html


.... and here's another useful (and related) article from the PMWF watch school:

http://www.pmwf.com/Watches/WatchSchool/How%20to Resize%20Bracelets.htm

April 5, 2012 at 1:01 PM Flag Quote & Reply

johngo
Member
Posts: 8

Damn, I considered myself lucky for strap changes on the Spationaute III because it has drilled lugs.

So from what I read there is not really a substitute in finding spring bars that fit nicely?

September 4, 2015 at 11:35 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

The almost NOS Yema Spationaute III, which I bought right at the beginning of this year, came fitted with a dark blue and black Rewa brand 'rally' strap. It also came supplied with the original plain dark blue leather Yema strap, which contained the pins and tubes. :)




See page 13 of the Yema N7 and N8's spotted thread for more details.

My first thoughts had been to re-fit the original Yema strap - using the original cinched pins and tubes - but so far I've relented.

I remember asking the seller what he had used to fix the Rewa strap - and his reply was something like 'fat Citizen spring bars'.

They're not ideal - in that their ends don't go as far into the drilled lugs as I would like, but they seem to work, after a fashion. :/




Even though they may have fatter tips than normal spring bars, their (double) shoulders are preventing them from expanding further into the drilled lugs. I presume these are nominally 22mm 'fat' spring bars*. Their (approx.) dimensions are as follows: 25.5mm overall length (uncompressed); 19.0mm x 2.0mm Ø centre tube; 1.4mm Ø extensions with 1.2mm Ø tips. And that's where they fall down in my opinion. The drillings in a Yema Spationaute III's lugs are 1.4mm Ø. If you plan to go this route, it might be a better idea to go for the next size up (24mm) and cut / grind off the tips and double shoulders, so that the 1.4mm Ø extensions protrude into the lug drillings.


*Edit: these look close (although the centre tubes aren't quite as long):

http://www.ebay.co.uk/itm/CITIZEN-PART-509-00138-SPRINGBARS-2-x-S-BARS-22mm-x-2-0mm-x-1-2mm-ENDS-/221851695579


September 5, 2015 at 3:30 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

Correction, possibly. :P

I think the Italian gentleman who sold me that Spationaute III and fitted the Rewa 'Rally' strap may already have done his homework.

That Australian eBay seller who is listing the Citizen 22mm 'Fat' spring bars with 1.2mm ends (p/n 509.00138) is also listing these:


http://www.ebay.co.uk/itm/2-x-CITIZEN-509-00181-DOUBLE-FLANGED-SPRINGBARS-23mm-x-2-0mm-x-1-2mm-ENDS-/350973464636




In the seller's photo, they look a lot closer to the dimensions I measured: 25.5mm overall length and 19mm tube length.

I wonder if Citizen do these in other (longer) lengths, besides 20mm, 22mm and these nominally 23mm (p/n 509.00181). :/


September 5, 2015 at 6:18 AM Flag Quote & Reply

johngo
Member
Posts: 8

Hi Paul, So you recommend the ones in the last post for best fit if I'm not into dremelin' my own parts, am I right? English is not my maternal language so I'm getting a bit confused. ;)

September 5, 2015 at 2:19 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

John.

If you're looking for an 'off the peg' solution for quickly removable spring bars for a Spationaute III, without resorting to dremeling, then they're probably as good as anything you'll find - but I wouldn't personally recommend using them to anybody. As I wrote previously:

They're not ideal - in that their ends don't go as far into the drilled lugs as I would like, but they seem to work, after a fashion.

Try googling the expression 'After a fashion'. ;)


PS - and if perchance you're considering fitting a NATO strap (Heaven forbid), I certainly wouldn't use them in that application.


September 6, 2015 at 5:18 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

But your mention of 'Dremelin' gave me an idea. 

Whereas the 22mm or 23mm (whatever they are) Citizen 'fat' springbars tenuously holding that Rewa strap onto my Spationaute III aren't as long as I'd ideally like them to be (for modding), it was clear that they were under compression when fitted. So I decided to take a gamble and lightly modify one of them, by grinding off just the outer shoulders, which would make a new 1.4mm Ø 'step' to engage the lug drilling, rather than relying on the loose-fitting 1.2mm Ø tip.




It might not be pretty, but it worked. :)




Though still recessed, the ends of the modded spring bar are now visible in the lug drillings - they weren't before. 8)


September 6, 2015 at 1:08 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

I'm never averse to 'correcting' my earlier assumptions / statements - particularly when they were based on my knowledge at the time.


Earlier in this thread I'd written:

Because of the diameter of the watch head - anything around 40mm, say compared to the maximum 24mm width of a bracelet ....

it isn't always possible to use a normal (typical cheap ex-eBay) bracelet pin pusher on these bracelet to watch head fixing pins.

Then there really is only one solution - the 'proper' tool for the job - one of these:




(on February 23, 2012 at 6:48 PM) and followed later that evening by ....

In my opinion, there is only one proper way to get the strap pins out of a Yema Spationaute III or N8 Flygraf - the Seiko S-926 tool.


Those statements were based on the fact that some time previously, I'd bought a cheap Indian or Chinese made bracelet pin pusher tool on eBay whose 'jaw width' was just a shade over 25mm (hence wasn't even wide enough to accept the lugs of a Spationaute III), compared to the nearly 40mm opening of the Seiko S-946 tool.  I was looking on eBay earlier in the week and spotted this:


http://www.ebay.co.uk/itm/271876942172 406115 Link Pin Remover Adjuster Watch Band Bracelet Strap Repair Tool Free Part

Clearly similar in design to the one I'd bought years ago, but going by the seller's 5th photo of rather more generous proportions:




Seeing as they were only £2.99, I thought what the heck - and bought one. :P The 'jaw width' of this tool is somewhat wider. :)




Indeed plenty big enough to accept the lugs of a 43mm Spationaute III (leaving plenty of clearance for pushers and crown too). 




It goes without saying that quality is not great (thread alignment) - but it's a cheap usable tool. Here I'm using it to 'countersink' the Yema fixing pins on my most recently acquired 'fixer-upper'. (Note the two tiny strips of 'Duck' tape on the lug to prevent marking.)


September 20, 2015 at 6:21 AM Flag Quote & Reply

johngo
Member
Posts: 8

Nice Paul you can do it with a cheap tool too :) Thanks for sharing.

November 11, 2015 at 2:56 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

johngo at September 4, 2015 at 11:35 AM

Damn, I considered myself lucky for strap changes on the Spationaute III because it has drilled lugs.

So from what I read there is not really a substitute in finding spring bars that fit nicely?


John.
Besides those 'Fat' Citizen spring bars (which ideally need one flange grinding off) that I've already written about ....
I may have found another possible solution for 'quick release' spring bars for the (43mm dia.) Yema Spationaute III.
Purely by accident, I stumbled across this listing by an Italian eBay seller:



The seller's description is a bit vague - the only dimension they actually give is '22mm', but they appear to be in the right proportions.
The critical dimension, to get a 'rattle free' fit in a Spationaute III's lug drillings (arrowed in red) needs to be 1.4mm diameter.
Not a cheap solution, but it might be worth asking the seller for more info. :/

January 2, 2016 at 5:38 AM Flag Quote & Reply

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