Service: Omega Speedmaster Moonwatch 105.012-66 calibre 321

IMG_0776Having done a “modern” Moonwatch the other day, today, it’s time for the real thing. Kurt from Switzerland sent this one in for a service. I must say I feel quite chuffed to get a Swiss watch sent from Switzerland for a service 😉

My regular customer and reader Anders is preparing a blog entry about Moonwatches and the Lemania connection, so I won’t go into any detail here, and leave it to Anders to fill you in on all the glorious details in a couple of weeks.

Onwards and upwards, it’s time to service this beauty…

IMG_0777I haven’t adjusted the lift angle on the timegrapher yet (this movement has a 40 degree lift angle), so the amplitude is really around 240 degrees, and we have quite a bit of a beat error.

IMG_0778If you have ever approached me about case polishing in the past, you know that I’m quite conservative, and generally try to dissuade you from having your case polished. This case back is the reason why. The “Speedmaster”, Omega symbol, and dragon have been polished away.

IMG_0779Below the dust cover lurks the beautiful calibre 321 movement.


A bit of dirt under the bezel.IMG_0787

And off we go!IMG_0792

Half way through the chronograph.IMG_0802

Almost there.IMG_0804

The driving wheel for the chronograph gears comes off.IMG_0805

And I can turn the movement around and start on the bottom plate.IMG_0815

Just the keyless works to go.IMG_0825

The gear train.IMG_0826

The old mainspring in the barrel. The gear on the barrel lid drives the hour hand of the chronograph, and it has a friction clutch which is slipping during normal use (e.g. when the chronograph is not started).IMG_0827And it all goes into the cleaning machine.


The case and bracelet are cleaned in the ultrasonic cleaner.IMG_0829

The usual suspects get epilame treatment.IMG_0830

All parts cleaned and ready for reassembly.IMG_0893

The new mainspring has arrived.IMG_0894

And I can start off with the gear train.IMG_0895

I put together the parts of the bottom plate needed to hold the mainspring barrel and the winding gear.IMG_0896

With the escape wheel and balance in, the movement starts beating.IMG_0897

I still have a sizeable beat error. On the 321, the beat error is corrected on the collet, so you have to take the balance out and slightly turn the hairspring collet and test again.IMG_0899

0.9ms beat error is good for collet adjusted, and I have a very healthy amplitude.IMG_0907

With the movement ticking as it should, I can start off on the chronograph layer.IMG_0908

This is a slow process, as each parts has to be put in its correct place, tested and lubricated as I go along.IMG_0909

chronograph is back together.


The depthing is adjusted under the microscope.298-02

And done.IMG_0910

Now the rest of the bottom plate comes together.IMG_0911

Ready for the dial.IMG_0913

Dial and hands go back on. The chronograph hour hand isn’t quite right yet, and I take it off again and position it exactly at 12.IMG_0914

And I can case the movement.IMG_0915

The new gasket gets a bit of silicone grease and goes in.



As the dust cover is a bit dull and discoloured, I give it a quick polish.



And we’re back in business! The hour sub-dial of the chronograph moves constantly, as the minute counter moves from one minute to the next once a minute has passed.

If I ever have enough budget, I will want one of these for my collection. And it’s got to be the 321 calibre!

7 thoughts on “Service: Omega Speedmaster Moonwatch 105.012-66 calibre 321

  1. Hi guys,
    isn’t the dial a service dial? and did they even make 321 cal. Speedy’s without the applied Omega logo?

  2. Hallo Christian
    schön zu sehen, dass die Revision meiner Uhr immer noch in Deinem Archiv ist. Ich habe den Link Freunden gesendet und einige hier infiziert mit dem Virus.
    Weiterhin viel Freude beim “arbeiten”. Ich hab leider noch keine Uhr revidiert, zu viele ander Projekte.
    Beste Grüsse
    Kurt (321 works stil perfect!!)

  3. Dude – that’s no dragon! It’s a hippocamp, a stylised sea-horse 🙂

    Does “depthing” refer to the depth one gear tooth fits inside the corresponding gap or to the vertical component – the tooth to tooth facing?

    Shame you didn’t have both speedies on the bench at the same time – would have made for a nice comparison piece!

    • Oh dear, I should have known that 😉
      Looks like a dragon, though…

      Yes, depthing is adjusting how far the gears engage with each other. If too close, the movement will stop when the chronograph is started. Too wide, and the second hand will be jumpy.

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