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After a long and expensive waiting and experimenting period, I have finally reached my goal: a modern mechanical watch under 7mm total thickness.

Now I have a great looking, ultra thin, large diameter, all stainless, water resistant, high beat manual wind watch :-!:-! patting myself on the back .. hehe.

It was made possible by this Lorinser quartz watch from Alixpress:

https://www.aliexpress.com/item/Swi...uxury-brand-men-s-waterproof/32968550560.html

Unfortunately not available from the link any more, but some other seller is offering it as a pair (male + female sizes).

I waited so long for this watch that I took it apart straight away, not taking any pics of the original. This is not a big problem, since only the hands look different in the finished product. Original hands were pretty straight forward and boring anyway.

Instead of the "Swiss Quartz" movement (Ronda), the watch is now running with a slightly modded ST1812 (2892 clone). I removed the rotor from the autowinding assembly, and put back the rest of the bridge. This protects the otherwise exposed gears, and also maintains hacking. Had to grind down the sticking-out rotor support a bit, quick and easy with the dremel.

The case is all stainless. Three separate parts, easy to open and close.
Caseback is held with 4 screws, 0.8mm thick in the center. Top part can be opened with a case knife.
Solid link stainless bracelet, very comfortable to wear.
42mm diameter without crown.
Sunburst dial is 37.5mm in diameter.
Originally 6.75mm total thickness (with 1.25mm thick flat mineral crystal, resting on an L gasket). Crystal diameter 37mm.
Now 6.65mm total thicness (with 1mm thick crystal)
Should possibly come down to 6.5mm with a correct height L gasket (havent found one yet, normal ones are designed to support thicker crystals).

I have not done a "proper" job, but it works for me :)b-)

Some quick pics with the phone:
 

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I was wondering if you removed the barrel clutch during this process, because that will usually add 20%-35% to the PR?
 

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Looks like a lot of effort, but you got exactly the watch that you wanted, so well done. Did you do anything with the calendar mechanism, or just leave it hidden under the dial?


I'm now thinking that it is a shame that the Dixmont DG69 movement does not seem to be more widely available. It has the same thickness as the 2892 but is available in a hand-winding version i.e. without the auto module. There is surely an opportunity for a microbrand.
 
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I was wondering if you removed the barrel clutch during this process, because that will usually add 20%-35% to the PR?
Excuse my lack of knowledge but what do you mean by "PR"??
Looks like a lot of effort, but you got exactly the watch that you wanted, so well done. Did you do anything with the calendar mechanism, or just leave it hidden under the dial?

I'm now thinking that it is a shame that the Dixmont DG69 movement does not seem to be more widely available. It has the same thickness as the 2892 but is available in a hand-winding version i.e. without the auto module. There is surely an opportunity for a microbrand.
PR would be power reserve i guess.

I do not know what and where is the barrel clutch :think: :-s

It was about an hour's work, and relatively straightforward - since I did not try to do a "proper" job - as can be seen from the grinding marks :)

From cost point of view, I dont think there is a better option than modding the 2892 clones. In my first ST1812 modded watch, I made a small part to fit into the place above the hacking lever and did not put back the bridge. It works well, but at the back of mind, I think that the "open" gears are vulnerable (they are not, as long as the watch stays closed).

With autowinder removed, it gets to a _total_ thickness of 4.65mm. This is important, since some movements have taller cannon pinion / second hand "pin" (dont know what it is called). For example, the Miyota 9015 I have is 6mm total, while the movement thickness is only 0.1mm more than the ST1812 (which is 3.8mm).
 

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Did you do anything with the calendar mechanism, or just leave it hidden under the dial?
It is just left under the dial. The date wheel moves freely and a single faint click of date changing around midnight is not something to worry about. I might try drilling a date hole in the dial later. Need to practice first with a cheap dial. Finding a 37.5mm dial that goes well with the ultrathin look is a task as well...
 

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PR would be power reserve i guess.

I do not know what and where is the barrel clutch :think: :-s
Sorry - Yes, PR is Power Reserve.

I am not an expert in watchmaking, or working on mechanical movements. Heck, I don't even like opening up a watch unless the battery needs changing. This is above my comfort and skill levels.

The area that contains a mainspring is "the barrel". Some watches have two mainsprings for greater Power Reserve (Double Barrel movements). In an automatic watch the mainspring is not attached on the outer edge, but instead is designed to slip against the inner barrel when fully wound. Most hand wind watches affix the outer end of the mainspring to the barrel wall. On a Tongji, it's relatively easy to hook the outer end of the mainspring to the barrel wall, but these movements were originally designed a hand winders.

8_day_pocket_watch_1020_010.jpg

In the above picture, the five notches hold the mainspring until the tension at full wind becomes too great, and the end of the mainspring pops out of the notch and slips to the next notch. On many hand wind movements, the mainspring is not allowed to slip, being attached to the barrel wall.
 

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The area that contains a mainspring is "the barrel". Some watches have two mainsprings for greater Power Reserve (Double Barrel movements). In an automatic watch the mainspring is not attached on the outer edge, but instead is designed to slip against the inner barrel when fully wound. Most hand wind watches affix the outer end of the mainspring to the barrel wall. On a Tongji, it's relatively easy to hook the outer end of the mainspring to the barrel wall, but these movements were originally designed a hand winders.

In the above picture, the five notches hold the mainspring until the tension at full wind becomes too great, and the end of the mainspring pops out of the notch and slips to the next notch. On many hand wind movements, the mainspring is not allowed to slip, being attached to the barrel wall.
That is definitely something for the professionals, I cant imagine doing it successfully myself. I also dont miss the extra power reserve.

I have some broken movements lying around, might try to open the barrel on one of them to look inside. Personally I like the idea of not winding to the maximum - can only be good for the life of the watch.
 

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This is brilliant .. I'm surprised that it fit did you need to do anything with regard to the stem height (distance between dial plane and stem center).
 

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This is brilliant .. I'm surprised that it fit did you need to do anything with regard to the stem height (distance between dial plane and stem center).
It is not perfect, but good enough for me. I will not feel confident selling it to someone, but wear it without any issues myself.

Stem height of the Ronda 762 is 1mm and for the ST1812 it is 1.5mm. There is no room for raising the dial due to the extreme thinness of the case. I had to "fiddle" a bit when inserting the stem back, but it worked out. The case back holds the movement flush against the dial. Winding the watch, pulling/pushing the stem, setting time, quick setting date (even when we dont see it due to the dial) all work fine.

I plan to make another version with the top part of the case replaced with a low domed acrylic. Then I can raise the dial, and might even manage to keep autowinding in place by grinding out the caseback a bit. Target is to get under 8mm total thickness with automatic winding.
 
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