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020-Background Information and Problem Statement

3503 Views 48 Replies 6 Participants Last post by  peter.mone

Seiko Suwa’s caliber 56 was introduced in late 1967 in the Seiko Lord Matic line, later to be followed by the 56 Duotime, 56 King Seiko/King Seiko chronometer/chronometer and the 56 Grand Seiko lines. In total, the calibre 56 family is comprised of the following caliber variants: 5601A, 5605A, 5606A, 5619A, 5621A/B, 5625A/B, 5626/AB, 5641A, 5645A and 5646A. By the time it was introduced, calibre 56 was Seiko's, allegedly even the world's first automatic movement with a date AND day quickset function.

Setup of the 56 QS rocker:

All of the date/day+date calibers except for 5619A use the same calendar quickset construction with a corrector rocker (P/N 981560), wherein a 4-toothed corrector wheel is stacked on top of an extended shoulder of the setting wheel below it. This assembly is then held in place with a hollow, straigth shouldered post friction-ed into the rocker plate, with a head (or flange) on top to keep the wheels captive. A convex metal washer is present between the bottom of the head and the top of the wheel stack. The following illustration shows the cross-section of the assembly:

Line Text Parallel Diagram Slope

The next picture shows the calibre 56 rocker with a white plastic corrector wheel in its natural habitat:

The complete rocker assembly is – apart from the corrector wheel – comprised of the following parts (left to right): the setting wheel with post, on which the corrector wheel is friction-fit, a washer holding the corrector/setting wheel assembly down and a flanged post that both fixates the assembly to the rocker plate and also acts as the main axle.

Metal Brass Fastener

The following sketch outlines the shape and dimensions of the rocker corrector wheel in detail:

Diagram Line Circle

In the next two illustrations, the pivot/central axle and setting wheel dimensions are covered:

In order for the friction fit to function properly, the inner diameter of the corrector wheel needs to be minutely smaller than the outer diameter of the setting wheel post it is fitted onto. This means, that the corrector wheel main frame is under tension constantly even if not actually used.

Changes to the QS rocker corrector wheel over time:

Latest information shows that the very early calibre 56 Lord Matic models (approx. 1967/12 to mid of 1968) had a metal corrector wheel fitted, either very firmly set or fixed to the setting wheel post. This was determined by examining early 56 LM watches and a late 60s Seiko oiling chart that specifies an oiling point for the 56 QS rocker - which is only necessary if a metal part was used. This also suggests that early 56KSs (562x-7000) were equipped with a metal corrector wheel.

The metal construction was however abandoned quickly, since it did not possess any safety measure against damage to the calendar if the quick set were to be activated in the “forbidden zone “ (approx. 08:00 pm to 01:00 am), leading to damaged calendar parts.

Therefore, from mid/end of 1968 to the end of calibre 56 production in the late 70s friction-fitted plastic/resin corrector wheels instead of fixed metal wheels were employed as the safety measure of calibre 56 to prevent damage due to improper use of the calendar quick set function when the day/date driving wheel/finger is engaged with the day/date disks. The plastic corrector wheel was intended to slip over the setting wheel post and thus prevent the system from getting damaged.

Thus, over time, three different types of corrector wheels have been found, a metal one, a plastic (black) one and a resin (grey) one, all three of which are original Seiko. The three types are depicted below:

Auto part Transmission part Metal Hardware accessory Bicycle part

Cause of the 56 QS plastic corrector wheel issues:

While switching to the plastic corrector wheels may initially have prevented damage to the calendar mechanism, unfortunately a good portion of calibre 56 movements with either date or day/date can no longer be quickset due to a crack in said plastic corrector wheel.

The corrector wheel is friction fitted onto the setting wheel post. Thus, it is under constant tension load even if not employed. Apparently, the plastic used for the corrector wheel did either become brittle and/or shrunk over time due to aging of the material, so that the abovementioned slipping function is no longer present. Under these circumstances, one careless use of the QS function with the calendar mechanism engaged will probably be sufficient to break the wheel, which means that there is no longer sufficient friction transfered onto the (broken) corrector wheel to drive the date dial and/or the intermediate wheel for day corrector - thus quickset is no longer available.

On the other hand, even NOS parts in their original packaging are frequently found with cracks in the wheel and are thus no longer functional. It is thus possible that the change in material properties (becoming brittle) through aging or the shrinkage over time alone causes the wheel to crack. In both cases, the corrector wheel would crack due to (inherent) tension overload even if sitting idly on the setting wheel post.

The most common issue is a crack in the wheel mainframe between two teeth, in some rare cases, also broken teeth can be found. Below is a picture of a rocker with a black, cracked wheel and a second rocker with the grey corrector wheel removed, crack clearly visible:

Changes to other calibre 56 calendar components over time:

On another note, apart from the corrector wheel on the QS rocker, other changes were made to the calibre 56 calendar components. In early (pre 1969) calibre 56s, all calendar components are made of metal:

Watch Pocket watch Fashion accessory Jewellery Metal

Over time, three types of day fingers (one metal, two plastic versions) and two intermediate date wheels (metal, plastic) can be found (metal parts on the right):

Metal Plant

As can be seen, day finger type 3 (pictured left) has a triangular cutout for the date driving wheel pin. This enables the day finger to move out of the way in case that the QS were to be activated while the finger is engaged with the day wheel. Due to the lack of a separate DATE finger, no such functionality is present for the date wheel, though.

Function of the washer:

  • For both plastic and metal corrector wheel types, the washer regulates end shake of the setting/driving wheel assembly on the central rivet/post.
  • Furthermore, the additional tension (=friction) on the setting wheel most probably ensures smooth shifting of the rocker in quick set position from one extreme of travel to the other (i. e., between day and date quickset). When in quickset position and the crown is rotated one way, the rocker "rocks" over to the intermediate wheel for day correction. When the crown is rotated the other way, the rocker needs to shift back away from the intermediate wheel for day correction and then over to let the corrector wheel engage with the date dial teeth. Having a tension washer above the rocker's corrector wheel can help ensure the rocker moves crisply before the wheels start to rotate.

Calibre 52 quickset setup:

Next, let's look at the quickset setup of calibre 52, corrector rocker P/N 981001. The construction is very similar to calibre 56, the exact same types of parts are used. Unlike calibre 56 however, the corrector wheel for calibre 52 was metal over the entire production period of the calibre:

Brass Metal

Also, as can be clearly seen, the corrector wheel has a “gap” in the main frame, allow for undue tension applied to the wheel being released if the quickset mechanism were to be activated in the “forbidden zone”. Under these circumstances, the corrector wheel would minutely enlarge in diameter, thus allowing it to slip over the setting wheel.

The next picture shows a size comparison of calibre 56 (plastic, cracked) and calibre 52 corrector wheels:


Problem statement:

  • All variants of Seiko calibre 56 with calendar (except calibre 5619) use the same calendar corrector rocker, P/N 981560, the big majority of which is equipped with a plastic corrector wheel that in approx. 50% of the watches appearing is found to be broken, so that the calendar can no longer be quick set.
  • The root cause is considered to be the aging of the wheel's plastic, which leads to a change in material properties (becoming brittle) and/or shrinkage of the wheel. Therefore, the inherent tension of the wheel being friction-fitted to the setting wheel post alone may be sufficient to crack it.
  • NOS spares – apart from being scarce – are not really an option since the majority of these appears to be damaged, I. e., non-functional, too.
  • Obtaining functional parts through donor watches while costly is to be considered a bit of a gamble due to the high appearance of broken QS parts.
  • Furthermore, the longevity of the - currently intact - plastic corrector wheels is considered to be questionable.
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Open actions:

  • Follow-ups if required:
    • Evaluate calibre 5206 & 5216 calendar safety mechanisms
    • Compile procedure regarding rocker disassembly/reassembly
Thanks for getting the ball rolling, Hermann, this is an excellent summary. A few things I'll mention:

A) Might want to re-word the second half of this sentence to make the description of the assembled part a little more concise:

All of the date/day+date calibres except for 5619A use the same calendar quickset construction with a corrector rocker (P/N 981560), where a to rivet fitted to the rocker frame a driving wheel with axle is set, onto which the setting wheel is friction fitted.

B) Regarding the thin convex metal washer which rides above the setting wheel- I think endshake limiting might be one function, but another I see in components like this in other calibers (different manufacturers, too) is a function of smoothing out rotation of the part it acts upon, to promote more positive engagement with neighboring wheels. Otherwise these types of wheels can jump out of engagement a little more readily without such a drag-inducing washer. Just a theory, I've not tried a rocker without the washer installed to see what it does.

C) Interesting theory on three different OEM versions- I had seen that photo before of the metal, black, and grey plastic setting wheels, but had heard it posited (gossip) that the metal one was an aftermarket wheel manufactured after the caliber was discontinued. The presence of the metal wheels in early examples would certainly support your theory though.

D) Have you taken apart a 52 rocker to see what the setting wheel (with intentional split) looks like and measured the setting wheel itself? I don't have any 52 caliber donors laying around, but I think basing a solution on the 52 version may be promising. One thing to consider though is what the rest of the calendar parts are made of- metal as I recall in the case of the 52. The 56's day finger (one part that could get damaged if the setting wheel doesn't slip when quick-setting is forced in the forbidden zone) is made of plastic, which will not survive the same level of forces that a metal part will, and my guess is that a plastic setting wheel of the same dimensions as a metal one will slip more readily compared to the metal one, all things being equal otherwise.

N.B. I'm not familiar with this type of structured discussion (though I feel it would be useful for me to learn!). Should I be putting my points A, B, C, D all in separate posts? Feel free to correct and point me in the right direction to keep things moving smoothly and easily understood as we progress.
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The summary Hermann has provided is an excellent summary and sums it up quite well.

As we likely all know a few of the images came from the Seikomatic Archive page that outlines this design issue.

I read through the Google translated version but also had a Japanese colleague confirm the translation from the page in the various key areas.

This page is the authors theories on the problem and this is based upon their own research and information from watchmakers. They claim that the part was originally metal but was later changed to resin to prevent damage when the date was changed in the "forbidden zone".

The three versions pictured are all original Seiko parts from different production periods.

The description on the Japanese page translate as Left: Fixed gear made of metal, Middle: same in black synthetic resin, Right: same in grey synthetic resin.

When it states fixed this means non-movable not fixed as in corrected.

Just for accuracy these are all Seiko parts for use in Seiko products, so they should not be referred to as OEM. OEM would only be relevant if it was a 3rd party manufacturer who supplied the part or if it was Seiko supplying the part to another company for their use.

The other thing that this article states in the opening sentence is the 56 was the world's first movement with a day and date correction device. I had not heard this before and do not know if it is true but is interesting. If this is not true I do not know how it impacts the believability of the other statements in the article.
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An excellent and comprehensive summary Hermann, thanks for putting that together.

Interesting to see that the first execution had a metal setting wheel, I wasn't aware of that.

Another reason for choosing a plastic/resin wheel rather than a metal replacement may also have been to remove the need for lubrication, plastic parts being generally 'self-lubricating'.

I suspect getting an oiler through to the main axle to lubricate the setting wheel wouldn't be possible when the unit is assembled and is something we may need to consider in any proposed all-metal solution.

Noah's point about damaging the day finger in the 5606 is a good one and is (as I'm sure we've all experienced!) a problem common to other Seiko calibres. Would it be an option to investigate replacing the plastic finger with a metal one too as part of the wider solution, as this would give more leeway on the amount of force the whole QS system could handle?

One last thing... I've never separated a QS rocker out myself so I have a question about the rivet/rocker plate. Is it possible to reassemble it or is it effectively a sealed unit that once separated the end of the rivet is trashed?


PS. Like Noah, I don't participate in this kind of debate very often so please let me know if I/we need to do it differently.
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According to the Seikomatic page and Hermann's description the choice of the plastic was to allow the gear to slip when too much frictional torque was present. This would happen when performing a QS during the "forbidden zone".

The article also states that with wear and aging the gear may slip under lower pressure and also render the QS unusable. Consequently the gear does not have to be broken to not function but just slip too much.

There needs to be a balance found that will allow the gear to slip enough to not cause damage to the mechanism, but the slippage must be controlled and consistent so it does not end up slipping too much over time.

Looking at the rivet I am also not clear on how it is held in place and if this is able to be reassembled easily. Unfortunately the cross section does not give any clues to this.
Fantastic guys, these are exactly the sort of replies I was hoping for :)
Great info & great discussion.

The structure of your replies etc. is perfectly fine - in the meeting room, I would usually use paper cards and use one card for each discussion item. Since we do not have the possibility of a live meeting and we are also a rather small group I do however think everything is good the way it is.

@ Noah:
A.: I did have some hard time phrasing this sentence - could you kindly suggest an alternative?
B.: I am afraid I do not fully follow - do you mean, the whole rocker would "jump" out of position? I do not see how they wheels would have the possibility for radial movement...

C.: I would say the metal wheel is more than just a theory. I know the rumours of the part being aftermarket, also because I am at least partially responsible for them :) The article on Seikomatics is a solid basis for this IMO, plus Peter examined one of his early (Oct 1968) LMs upfront and found it equipped with a metal rocker.
D.: I bet Peter is buring to say what he has done regarding a solution based on the calibre 52 rocker :) Let's please wait a little more regarding this please until we get to the "solutions" part.

@ Anthony:
Some excellent info their, many thanks for having the article translated!
It was exactly the "modified" and "fixed" terms of the google translation that I had my problems with understanding them.
Also thanks for the info regarding OEM - I will correct this in the summary.

Also very intereresting - the remark regarding calibre 56 being the worlds first calibre with D/D QS. While I definitely cannot comment on this, it should be Seiko's first at least AFAIK - I will also put this in the summary.

Re proper slippage: let's please keep that in mind for the next "milestone" (goal statement and scope of project).

@ Rich:
Great discussion points.

Re lubrication: I agree that the plastic setting wheel might be considered self-lubricating - but then I do not see any indication of lubrication being required in the calibre 56 servicing guide. Also please note: friction forces under "normal" conditions would occur between the (metal) driving wheel/post and the central rivet.
On another note it might be possible to reduce frictional forces between the metal setting and driving wheels in the early correctors - that depends on how this assembly was generated. I am looking forward to Peter commenting on this :)

Re replacing the day finger: please keep this point in mind for the next "milestone", which will deal with the goals and scope of the project.
Personally, I would say: I have handled/worked on a good three dozen calibre 56s in the last two years, of which maybe one or two had issues with the day finger (amongst many other problems). So I (as team member, not mod!) would think that this in not a high-priority issue since parts would be readily available - quite unlike for the QS corrector/setting wheel.
But let's discuss this in the next thread, ok?

As for taking the rocker apart: I hope Peter and/or Noah will comment on this. I do not have the possibility to do this myself (no suitable tools), but from what I have gathered so far disassembling and reassembling the rocker appears to be a reversible process to sufficient extend.

One more thing that I really would like to discuss - especially after Anthony mentioned the point of the setting wheel more or less wearing out w/o cracking: what do you think is really causing the damage, maybe there are several root causes?

Thanks again and looking forward to hearing from you all!

P. S.: Peter - regarding the Oct 1968 LM - which parts of the calendar are made of metal?
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@ all: the information received from you has been included in the summary.
Also, I have tried to give it better structure to make it easier to read.

Please also take a look at the "action tracker" (2nd post) - I will keep this updated on the most important follow-ups.

The metal wheel is real - let me explain my theorie, that it must be origin Seiko, not OEM:

  • The 5606 Tech. Manual shows no oiling point at the day/date corrector wheel rocker - for the day/date finger is made of plastic.
  • The 5206 Tech. Manual shows an oiling point - for this day/date finger is made of metal.
  • In my large old origin Seiko "List of lubrication parts" you can find an oiling point for the 5606 day/date corrector wheel rocker with the remark "tube"! You don't lubricate a tube with a plastic gear around I think.
  • The 5206 don't exist in this list - for this caliber was engineered later than the 5606.

A closer look to the metal wheel I found in a LordMatic 5605 sn 8O2827:

I tried to analyze this metal day/date finger. At my opinion he is constructed as "1piece", the finger and the wheel don't move independent like the plastic version does. I've made closer photos "in action" too and you can see that there is no other plastic part involved. The day finger etc. is also metal (sorry, not to be seen in my photos).

Lets have a closer look to the
day/date corrector wheel rocker of the 52x6-family:

The wheel construction is the same as by the 5606 - but without any plastic parts.
The dimensions looks identical. Please respect that the plastic gear is broken.

The rivet of the 5606-tube is large enough to fix it again to its plate.
Unfortunately I dont have the right tools for a correct measurement ...

I was been late with my response, please excuse for I have to restore my 2nd backup hard disc of 1TB who has crashed today. Now I know well why I make backups minimum twice ;-)
Best regards,


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Excellent Peter, many thanks!

Following the logic of the "list of lubrication parts" - i. e., the existence of a lubing point in this early guide as opposed to the absence of a lubing point in the latter 5606 servicing guide - one thus must assume that the early 56KS pieces were equipped with a metal rocker, too!

I guess this would make sense, since the first 56KSs (562x-7000) were introduced in 1968/08.

I forgot to show how simple it is to disassemble the day/date corrector wheel rocker. All you need is a staking tool:

The little puzzle you can reassemble same way ... but it's not a good idea with the broken plastic gear :grin:
Best regards, Peter


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Last for today a complete look at the movement of my LordMatic 5605 sn 8O2827, all metal, no plastic :)


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Thanks, Peter!


Here's what I found when looking through my calibre 56 spares bins:

1. there are three types of day fingers, the early calibre 56s were equipped with metal ones
2. there are two driving wheels, again metal for the early movements:

Coin Money Metal Currency Silver


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A: I'd propose we change the sentence to something like this:

All of the date/day+date calibers except for 5619A use the same calendar quickset construction with a corrector rocker (P/N 981560), wherein a 4-toothed corrector wheel is stacked on top of an extended shoulder of the setting wheel below it. This assembly is then held to the rocker plate with a straight-shouldered post, with a head (or flange) on top to keep the wheels captive. A convex metal washer is present between the bottom of the head and the top of the wheel stack.

B: Let me re-phrase. Tension washers such as these are often necessary to allow side-to-side motion of the assembly before the engaged wheels beneath start rotating. Without it, in some cases the wheels could spin freely in between engagement points before the assembly could shift into engagement with the wheel (or date dial in this case) next to it. When in quickset position, you rotate the crown one way, and the rocker "rocks" over to the intermediate wheel for day correction. When you turn the crown the other way, the rocker needs to shift back away from the wheel and then over to let the corrector wheel engage with the date dial teeth. I'm guessing that the engineers wanted to ensure smooth shifting of the rocker from one extreme of travel to the other. Having a tension washer above the rocker's corrector wheel can help ensure the rocker moves before the wheels rotate.
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disassembly of the rocker: Like Peter, I also use a staking set to disassemble the rockers, most of the time without damage to the parts involved. Because I've always been trying to save the plastic wheel, I don't allow it to rest upon the stump when removing, but rather try to catch opposing sides of the rocker plate in a V-block, and then push the central post out from the bottom. One can almost use the back of their tweezers to tap on the stake- the post isn't really riveted in place so much as friction fit. Same with re-installing the post- just a few light taps with the lightest weight watchmaker's hammer is sufficient to push the post back in position. If it goes too readily, then maybe spreading the edge on the bottom of the post might be in order, but that is up to the watchmaker's discretion for each individual rocker. I think that it can be taken apart and put back together at least a few times without issue, if done carefully to avoid distorting the plate, post, or two wheels. Here is how I have been supporting the plate (though the v-block would be mounted in the staking set frame, not in a bench block as the photo shows):

Tonight I tried an alternate method, assuming that one does not care about the plastic wheel. If this is true, then one can support the assembly from below on the plastic wheel itself, and then push the post out from the plate. This method offers a little more safety to the rest of the parts (at the expense of additional danger of damaging the plastic wheel irreversibly), which might be desirable if a brand new 4-tooth corrector wheel is being installed anyways. It's also easier to set up- the V-block way can be a little tenuous to get everything aligned properly. Here is a shot of that method of disassembly:

And here is the re-assembly set-up I use- supporting the head of the post underneath, and using an open mouth punch from above that just contacts the plate:

What causes damage: Plastic is a poor choice as a long-term solution for anything, when compared to the more stable properties of metal. That is a simplistic statement, but underscores the nature of the problem as I see it- we're asking an awful lot of a plastic part to survive 40-some years in a high stress location (under constant tension if I understand the design correctly). As a related aside, another area I see problems relating to plastic changing its fundamental properties (such as size) is the day finger and date driving wheel of the 63xx/754x caliber families. Those parts are seemingly made of the same type of grey (and later green) plastic that the 5606 parts are, and over time they shrink to the point that they bind on the posts on which they turn. This is especially problematic with the lower torque output of the quartz 754x calibers, which can be enough to stop the watch or cause erratic running. In that case I've often wondered if the strong chemical solutions that unaware watchmakers have exposed these plastic parts to are causing them to shrink, but really I just think it happens with time. I think I had a 7548 a few months ago that I knew had never been serviced, showing the same shrinkage. So that would suggest that it isn't owing just to chemical solutions alone, if at all.
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I too separated a rocker last night (before reading the replies above) and it came apart much easier than I was expecting.

Having first pushed the plastic wheel off the rivet by stretching it at the split point, I then used an old roller remover to hold the rocker while I staked out the rivet (the blades being on the shoulder of the wheel below). It's effectively the same idea as Noah's v-block, but it gives the freedom to move the rocker around under the stake. One light tap and it came apart.

Having seen that Peter separated his by just holding it by hand under the stake (I'm assuming the Rodico is just in use for the photo) that already says enough about how easy they are to get apart.... but all roads lead to Rome as they say. :)

How many of these have you guys actually repaired?

I ask as I repaired the one I separated last night - gluing the plastic wheel back together (separating the break in the plastic wheel over a balance tack while gluing it to account for the shrinkage). It isn't elegant by any means, but the re-assembled rocker works for the quickset and slips as it should in the forbidden zone. Was that just beginners luck?

Also, while we are still in the scoping phase, I have another couple of wider non-technical questions/concerns. (If this is the wrong place or time for these Hermann, please let me know).

1) What is the ultimate goal here? Are we looking to just solve the technical problems/shortcomings, or are we looking to produce new rockers or parts that other people can purchase?

2) I don't have the facilities or contacts to produce a new plastic wheel (in either metal or plastic), does anyone else? If not then I suspect that we will have to approach a manufacturer. Does anyone have any experience in this area? Having parts made in China perhaps?

As I expressed to Hermann earlier, my concern is that we may have to have them made in the thousands before anyone will agree to manufacture them.

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Excellent contributions guys, many thanks!

I will update the summary with the information provided. Regarding the use of the staking tool - is it ok for you if I for now leave them as-is?
We will be coming back to this point at the end of the project again when we are talking about implementing solutions.

@ Rich: sorry to come in here again :) Actually, we are not even yet in the scoping phase - that will be next, once we are all set regarding the background info and what our problem is. Let's please wait with the discussion on scope and possible solutions until hopefully next week - ok for every one?

I know this requires quite some patience (for me, too ;-)) especially in this virtual setup where we are not working on the project at the same time.

Let's please discuss one more specific topic for this milestone:
The root cause for the problems with the plastic wheel.
Noah provided some very good information on this. My primary concern is something that Anthony mentioned out of the Japanese translation: that the plastic wheel may somewhat wear out/EXPAND and thus become non-functional.

Our current theory in a nutshell is the following, right?
- the plastic wheel is friction-fitted onto the driving wheel post under TENSION (i. e., the setting wheel inner diameter is minutely smaller than the driving wheel posts's outer diameter)
- over time, the plastic of the setting wheel either shrinks a little, or becomes brittle, which in turn means:
- it could crack all by itself simply due to tension overload while sitting idly on the post
- it will lose its sliding properties, thus crack if employed in the "forbidden zone"

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Summary updated to include the latest discussion points.

As mentioned above, I would like to direct your attention to the discussion on "root cause of the QS rocker plastic setting wheel issues".

No problem Hermann, I'm happy to wait.

I'd agree with Noah that the root cause of the problem is down to shrinkage over time more than exposure to chemicals or overuse - as evidenced by NOS rockers being split right out of the packets.

I've seen vintage watches in past in which their plastic movement or dial spacers have shrunk and I'm sure we've all seen "crazed" crystals which I'm pretty sure is caused by the same phenomenon.

When the manufacturers were fitting these plastic/acrylic parts, I suspect that performance 40 years down the line was of no concern.

One of the root causes:
"- it could crack all by itself simply due to tension overload while sitting idly on the post"

Yes, it is one of possible causes, but I think more the plastic material itself has the responsibility for cracking.

In the 1960s we have had plastic materials which contains more diluents than today.
I have made my physics formation in 1964 at the company BAYER, Leverkusen in Germany and learned also to handle with technical plastics, their strain, forming and repair methods like welding with heat and solvents like aceton etc. These plastics (at this period) where been well hard, but their production needs much more diluants as need today (if need ...). It was also known that these diluants are outgassing during some time periods and the plastics rests brittle later.

For me this will the predominant reason why the little plastic gear cracks inside the movement and is found already cracked in n.o.s. packages.
Regards, Peter
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