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Discussion Starter · #1 ·
Hi all,
I've recently become interested in watch design and possibly production further on down the road.
Long story short, I'm currently migrating to Australia and awaiting Visa approval so I'm filling my time with learning CAD/CAM and designing a watch being as I am not allowed to work.
I've managed to design what I think is a pretty sweet dive watch, fudging my way through by collecting bits and pieces of info on dimensions and tolerances and such, but there's one area of the construction I'm not too satisfied with. ( I have no watches i'm willing to dismantle in order to visually verify the mechanics so it's a lot of guess work)

My question is this:
Does anyone here know where I might be able to view some detailed drawings with exploded views and dimensions of various styles of watches, primarily dive watches? I've had a go at searching the web, but have only found very rudimentary drawings or cross sections which don't quite provide adequate knowledge on or illustrate the workings of rotating bezels and water-tight fixing of crystals within them.

I'm fairly knowledgeable on the majority of a watch's design, but I am perplexed by the rotating bezel system and crystal attachment for a highly water resistant dive watch with a unidirectional ratcheting bezel. I know a little of the mechanics; crystal fixing ring, click spring, gaskets, etc. as per this drawing: http://www.thewatchsite.com/index.php?topic=283.0 however, I just can seem to grasp the assembly concepts and principles.
Perhaps I'm making it more complex than it really is.

Furthermore, any exploded drawings of water-tight crown assemblies would be quite useful. Although I think I've got a fairly good understanding of that area, any precise drawings would only serve to help.
As I said earlier, I have but one watch with a rotating bezel and I'm not too keen on dismantling it without proper tools or know how, even though I realise that would be the best way to learn about the workings of a watch.

Thanks for reading, and thanks for any help.
Paul
 

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Quick tuppence worth from a diving instructor re 'O' ring seals; when machining the lands and mating surfaces for an 'O' ring seal you have to account for the compression and deformation of the ring in its recess as fitted. In a nutshell (and from memory of conversations with the dive tech who serviced all my school regulators and cylinders) a correctly machined land will cause the ring to take up the form of a square/rectangle with the corners chamfered off with all sides in equal contact and under equal radial compression when viewed in section. Well that's my understanding without further subject specific googling!
(update - I think the 4 corners bit related only to a tank valve to regulator 'O' ring land now I think about it. Each application will of course throw up its own set of pressure induced distortions, deformations and extruding forces to account for.)

If you want to know about hydrostatic and hydrodynamic sealing at high absolute pressures then you could do worse than look up your nearest scuba service tech and pump him for information. From experience they are totally immersed ( :roll: ) in their subject and relish the chance to gob off about the minuteae of hyperbaric seal form, techniques, materials, surface finish grades, Shore A hardness ratings, reliability and failure rates.... god it never ends. He was a brilliant tech though! This online calculator can do a bunch of the work for you I reckon...

ERIKS O-Ring Calculator

As a rule of thumb for an 'O' ring in compression with no relative motion between sealing faces I believe you look to provide 20-40% compression (as a function of the ring's cross-sectional diameter) when in the 'as fitted condition and aiming to fill 75% of the machined void. The width of the land should be machined to around 1.5 times the cross-sectional diameter of the selected 'O' ring and the inner diameter should be a fraction (1-2%) under the inner diameter of the 'O' ring to help retain it. Lands can be rectangular in section or trapezoidal with the wider side outwards. Any back-up 'O' rings go on the low pressure side natch.
I always treated 'O' high and intermediate pressure hose rings, camera gaskets et al to the merest smear of silicone grease prior to installation, just enough to put a sheen on the rubber and no more. Over greasing just attracts and retains crud and silt. Scrupulously clean assembly is a given, a particle of shed hair falling unnoticed onto the seal will trash £10k worth of camera (or watch) before you hit bottom. Similarly, over compression is as bad as insufficient compression so I'm lead to believe. I'll find out for real when I bung my first prototype in his cylinder testing rig and crank up the ats. I'm going for a rufty tufty hunk of boro-silicate dive light lens perhaps for the front glass just to see how far it can be pushed before it leaks or pops!

Which is the reason I found this section and why I pitched in a post? I'm thinking of trying the same thing m'self initially by designing and turning up a WR300mtr casing for a redundant cheapy movement! Think Jules Verne meets Admiralty Standard Pattern 'copper hat' diving dress with maybe a sliver of steam-punk chucked into the mix. I love the look of polished marine bronze and I think I've sussed out a rather novel parallelogram/pantograph style bracelet design to go with it. Trouble is I've got terminal 'C' drive issues with my main lappy and it's defying ALL attempts at resurrection, as soon as I get to the data retrieval stage I'll fire up AutoCAD on the mem sahib's PC and post a quick screenshot of progress thus far.

I am no horologist in fact although I've worked around machine tools all my life as a spark I've never had to chew metal with them until one particular project required it. My machining experience amounts to about 8 months thus far. I've been swinging Acad about for a good deal longer and it's a big help. The challenge now is to match the accuracy of my machines/abilities to the output of AutoCAD. So I'm going to start by lathing and milling it out at 2X finished size just to ensure that I can achieve somewhere near the required degree of accuracy on my little 'Zyto' lathe + 'TWIN' miller set up.

Guv
 

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Discussion Starter · #3 ·
Wow! Great post with heaps of info, much appreciated.
These are issues I hadn't yet considered, although I must have, at least subconsciously, because I've made such allowances for o-rings and seals.
The main engineering portion I'm having difficulty in grasping is methods of affixing bezel and crystal on a 10 ATM or better watch.
For example:
On a watch with a unidirectional rotating bezel, is the crystal inserted and fixed from within the case, through the back, or is it fixed from the face with a snap ring or some sort of threaded o-ring?
I've resorted to disassembling my Bulova Marine Star, but I still can't figure out how the bloody crystal is fixed (and can't even figure out how to remove it)and the bezel is quite a simple config with what I believe is a snap ring fitted in a groove. However, while rated as water resistant, the watch couldn't even take washing dishes without allowing moisture inside, so I can't really use it as a guide for my purposes.
I just need the fundamentals for the standards of practice in these two departments, if such a thing exists, and I can take it from there either sticking with convention or re-engineering the way bezel and crystal are affixed, which I suppose I could do anyway, but I'd rather have a working understanding of traditional methods.
I just can't visualise it and it drives me mad.

Thanks again for your well versed response and the time you put into it Guvnah.
 

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Wow! Great post with heaps of info, much appreciated.
Glad it helps.

These are issues I hadn't yet considered, although I must have, at least subconsciously, because I've made such allowances for o-rings and seals.
Ah yes, "allowances"... that reminds me; the over-arching consideration in all of it is the question of the interactions of tolerances, both in the machining and in the nominal dimensions of the ring as supplied. I believe best practice involves accurately measuring the selected 'O' ring and then 'machining to fit' for that specific ring. An easier or more readily accessible source of info might be a local hydraulic engineering firm; the performance criteria to which they must manufacture far exceed anything a dive watch is likely to be subjected to by an order of magnitude. If it's good enough to dynamically seal against 200 Bar odd of hydraulic oil in a ram it should be more than adequate for our humble 'static sealing' dutiies.

The main engineering portion I'm having difficulty in grasping is methods of affixing bezel and crystal on a 10 ATM or better watch.
For example:
On a watch with a unidirectional rotating bezel, is the crystal inserted and fixed from within the case, through the back, or is it fixed from the face with a snap ring or some sort of threaded o-ring?
I've resorted to disassembling my Bulova Marine Star, but I still can't figure out how the bloody crystal is fixed (and can't even figure out how to remove it)and the bezel is quite a simple config with what I believe is a snap ring fitted in a groove. However, while rated as water resistant, the watch couldn't even take washing dishes without allowing moisture inside, so I can't really use it as a guide for my purposes.
Then we're in the same boat Paul! :-!

I never had the guts to dissemble my Aqualand to find out but my very first pukka dive watch (name escapes me now but it was an adequate £50 full 200mtr rated jobby) went south after a few years hard use and the unidirectional component was nothing more than a stainless steel shim/thrust plate come "Bellville" washer with a protecting pressed out tang to engage the ratchet machined on the underside of the bezel. I can't recall how the detatched bezel actually fitted though. Press fit? but I'm guessing here. Anyone?

As for sealing the crystal to the front face... should it be inserted from the back and snugged up against a gasket face by an internal ring? Seems the most elegant way of doing it but I have doubts about the capacity of such rings to seal effectively given the shallow thread engagement such a simple ring would need to have if the watch wasn't to hit 20mm in depth. Again I could be totally underestimating the amount of tourque that can be safely applied to a 2mm thick ring of s/s? Instinct tells me that I want at least 6 threads engaged but then the pitches become too fine to machine on my 'hulking geet" 3 1/2"!!! bench lathe. That's why I've defaulted to a front sealing regime using a simple axially compressed 'O' ring/s. At least until my knowledge and machining skills enable the consideration of other strategems. T'ain't pretty but I'm not asking for that initially.

I just need the fundamentals for the standards of practice in these two departments, if such a thing exists, and I can take it from there either sticking with convention or re-engineering the way bezel and crystal are affixed, which I suppose I could do anyway, but I'd rather have a working understanding of traditional methods.
I just can't visualise it and it drives me mad.
You and me both, that and machining the minute screws. S'gonna be fun finding out.

Thanks again for your well versed response and the time you put into it Guvnah.
more than welcome. I'm self teaching just by formulating the correct questions I think and if you hit upon a solution to the crystal sealing issue first then a heads up is all I'd ask.

--------------------

Just remembered something: somewhere on this forum is a well sketched cross section of a Seiko (I think) 1000mtr watch that had its crystal sealed by an internal threaded ring. I know I saved at least the jpeg to this drive so I shall have a trawl tomorrow and re-post it and possibly the link if I've stashed the whole thread.

ttfn

Guv
 

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Found that jpeg of the Seiko, looks like it installs from the front with a sealing ring to clamp it down.



Uploaded with ImageShack.us

Just got to find the associated article. From the above sketch I'm seeing three seals securing the glass at top bottom and circumference. The component marked "Glass fixing ring" serves to compress all three simultaneously. The compression of the lower ring is limited by the thickness of the "Dial ring" upon which the glass rests. The compression of the middle circumferential ring is determined and limited by the dimensioning of its land diameter and the depth of the machined lip on the bottom of the "Glass fixing ring" when screwed full down onto its shouldered seating. Ditto for the upper seal. As for installation I reckon the "Glass fixing ring" would be tightened down till it bottomed out and could go no further and the dimensioning ensures the effective compression of all three birds with one stone. Neat.

Just found the useful wiki entry for ISO 2281 which deals with water resistance of watches generally and ISO 6425 which is specific to dive watches.
http://en.wikipedia.org/wiki/ISO_6425
 

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Discussion Starter · #6 ·
Ah yes, "allowances"... that reminds me; the over-arching consideration in all of it is the question of the interactions of tolerances, both in the machining and in the nominal dimensions of the ring as supplied. I believe best practice involves accurately measuring the selected 'O' ring and then 'machining to fit' for that specific ring. An easier or more readily accessible source of info might be a local hydraulic engineering firm; the performance criteria to which they must manufacture far exceed anything a dive watch is likely to be subjected to by an order of magnitude. If it's good enough to dynamically seal against 200 Bar odd of hydraulic oil in a ram it should be more than adequate for our humble 'static sealing' dutiies.
Indeed, the way I've discovered the tolerances required for certain gaskets, o-rings, snap rings, what have you, is by browsing online catalogues of ring and gasket manufacturers. They provide essential information on groove depth/width in max and min dimensions. couldn't ask for more!

I also figured out the bezel conundrum in that same way, and it's exactly as you described. I was totally over thinking it and visualising a far more complex system for affixing it. I had already figured out the click spring for the ratcheting effect, so, that's squared away.

I had seen and studied the schematic you've attached, of the Seiko, and while quite helpful, the cross section does little for my visualisation of the mechanics and how it all fits together, thus the search for exploded drawings.

As for sealing the crystal to the front face... should it be inserted from the back and snugged up against a gasket face by an internal ring? Seems the most elegant way of doing it but I have doubts about the capacity of such rings to seal effectively given the shallow thread engagement such a simple ring would need to have if the watch wasn't to hit 20mm in depth. Again I could be totally underestimating the amount of tourque that can be safely applied to a 2mm thick ring of s/s? Instinct tells me that I want at least 6 threads engaged but then the pitches become too fine to machine on my 'hulking geet" 3 1/2"!!! bench lathe. That's why I've defaulted to a front sealing regime using a simple axially compressed 'O' ring/s. At least until my knowledge and machining skills enable the consideration of other strategems. T'ain't pretty but I'm not asking for that initially.
Now, as for the crystal....
I agree with the posed conflicts of a threaded retainer ring fed from inside, seating the crystal to a lip on the case just under the inner most diameter of the bezel. Not jiving logistically.
I have found tools for extracting crystals and 'pressing' them into the case, so I think, and I stress 'think', that there is a type of compression fitting ring either installed from the inside, or from the outside as per the Seiko schematic. I'm sure there are other methods, but these would be closely guarded secrets of extreme depth rated watch manufacturers I'm sure. The pressing method seems to be most common from what I can gather. There's also a lot of crystal glues and sealants, so I'm guessing that these are applied prior to pressing in order to ensure a water-tight fit??
Yet another thing I've noticed is that some crystals have an applied 'step ring' on the underside, inner circumference which leads me to believe it could snap over a lip or burl on the case dial opening in some fashion.

(last second add)
Ahhhhh yes! I see how they've done it on the Seiko! That's grouse!

Anyway, I've come up with the brilliant idea of taking my Bulova case with crystal still affixed to a jeweler and asking if they'll remove it while i watch. :-d

Once again, thanks heaps for all the time and effort put into the replies. It's great to have some really great feedback and insight.
I'll keep the research going and post what I discover, be it 'common knowledge' or otherwise.
Perhaps some screengrabs of my watch project will be coming soonishly. :-!
 

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PluckyPaul,

Your manufacturer will do all the enginerring and testing for you, you do not need to worry about all the tiny bits within the watch. Manufacturers go with that they know and have in store, which is the standard.
I'm a professional watch designer (b.s. industrial design) and have made a number of watch lines for companies.

Hope this helps.
 

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Bit of additional/supplementary info Paul; I found a very informative write up by Seele (geddit? :roll:) on the method used by Vostok for their Amphibia. The particular feature and narrative of which is to employ hydrostatic forces to actually increase the sealing forces rather than use the brute force, "clamp it till it hurts" resistive approach.

https://www.watchuseek.com/f54/vostok-amphibia-analysis-design-methodology-491757.html#post3604679

and also concerning the sealing regime on the Seiko 6309's...

http://www.network54.com/Forum/7844...diver's+watches+of+61+cal-+and+63+cal-+(scan)
 

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Discussion Starter · #9 ·
Your manufacturer will do all the enginerring and testing for you, you do not need to worry about all the tiny bits within the watch. Manufacturers go with that they know and have in store, which is the standard.
I'm a professional watch designer (b.s. industrial design) and have made a number of watch lines for companies.

Hope this helps.
Sweet! helps heaps!

Thanks also, Guvnah, for the links, great reads, good info to know.
 
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