Service: Omega Speedmaster “Moonwatch” Calibre 861

IMG_0411We’ve had the calibre 321 moonwatch, and now it’s time for Ketil’s calibre 861!

It’s in need of a service, and he also sent along 2 new pushers to be put into the case, and I’m happy to oblige. I love customers who already send me the right spare parts – saves me the work of hunting them down 😉

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And yes, it is time for a service. The amplitude is too low, and the movement is too fast, and there is a bit of a beat error.

IMG_0412Have I ever mentioned I don’t like case polishing? 😉 This could be wear, but I suspect that at some point, the case back was polished. Also, note the quite deep marks where people slipped with a case opener.

IMG_0415FIrst look at the movement, and you can see that the 861 is a bit different from the 321. The layout has been cleaned up a bit.

IMG_0420And the bottom plate. A very nicely designed chronograph movement.

IMG_0425As usual, I work my way through the chronograph layer by taking photos of each component with its screws, and the movement at every step. That makes reassembly a lot easier.

IMG_0435Slowly, but surely …

IMG_0443With the chronograph layer removed, I’m down to movement level.

IMG_0447The gear train is now visible.

IMG_0450The usual dirt and old grease, but nothing to worry about.

IMG_0452The old mainspring.

IMG_0454Now it’s time for the bottom plate.

IMG_0471All the parts cleaned and ready for reassembly.

IMG_0512I now turn my attention to the case. The old pushers are removed with a special tool.

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Now I clean the case before mounting the new pushers.

IMG_0513The new mainspring goes into the barrel.

IMG_0515I start off by putting the base movement together, as I first have to check that the movement itself performs as it should. No use putting the chronograph together only to find out that you have to get back to the movement….

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Now I put the bottom plate back together.

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WIth the movement beating as it should, I start on the chronograph layer.

IMG_0650With the chronograph complete, I can adjust depthing, and test the chronograph.

IMG_0655This is looking very good.

IMG_0657Cased, with the antimagnetic dust cover on, new pushers, and a new back gasket.

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The Speedmaster in all its glory.

15 thoughts on “Service: Omega Speedmaster “Moonwatch” Calibre 861

  1. Hello Christian,

    Sorry for bringing this pusher topic back up, but I need your help with finding the right tool for my pushers.
    I have an old Hamilton Diver Chronograph with screwed in pushers.
    The outer diameter of the pusher’s teeth is about 3,5 mm and the inner diameter of the teeth is about 3,25 mm.
    All the tools have only one measurement given, for example Bergeon has 3 different sizes of the tool 5901 (it looks like you’re using the same one) and they have sizes of 3,30 + 3,65 and 4,10 mm available.
    But I’m unsure about which diameter of the pusher they’re referring to.
    Inner diameter of the pusher’s teeth – so 3,25 and I need the 3,30 mm tool or on the outer diameter 3,5 and I need the 3,65 mm tool?
    Hope you can help.
    Thank you in advance!

    Regards,
    Peter

  2. Hello Christian,

    Sorry for bringing this pusher topic back up, but I need your help with finding the right tool for my pushers.
    I have an old Hamilton Diver Chronograph with screwed in pushers.
    The outer diameter of the pusher’s teeth is about 3,5 mm and the inner diameter of the teeth is about 3,25 mm.
    All the tools have only one measurement given, for example Bergeon has 3 different sizes of the tool 5901 (it looks like you’re using the same one) and they have sizes of 3,30 + 3,65 and 4,10 mm available.
    But I’m unsure about which diameter of the pusher they’re referring to.
    Inner diameter of the pusher’s teeth – so 3,25 and I need the 3,30 mm tool or on the outer diameter 3,5 and I probably need the 3,65 mm tool?
    Hope you can help.
    Thank you in advance!

    Regards,
    Peter

  3. Hi Chritian, I’ve been trying to research the pusher assemble on omega 1861’s. I am trying to investigate the method used for water resistance inside these pusher. Single gasket? Double gasket? With inner lubricant? I can’t find inner assemble diagram. You hand your hands on some spare pushers, can you elaborate on any guts you could examine when installing me ones? Thanks.

    • Depends on the model. Standard is a metal washer, 2 O-ring gaskets, and another washer if I remember correctly. None of those parts are available individually, but you can buy replacement pushers.

  4. Lovely watch, in much better condition than the one I started bidding on a few days ago:
    http://www.ebay.co.uk/itm/171105524799?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

    It’s gone a little out of my price range now though!

    Have you purchased the range of tools for pusher removal, or just the individual type as required? I was looking at the Horotec multifunction tool on cousinsuk, and although it’s expensive, it seems to make sense in the long run, what do you think?

    • Considering the state the watch is in, that auction is going to “silly money” levels. Very risky buying that, as it might just be a pile of junk…

      I’ve bought them individually every time I needed one, but it probably makes more sense buying a multifunctional tool…

  5. Antimagnetic dust cover? They were first adopted by if not invented by Taubert & fils and I think it’s generally accepted that they are movement holders. So screwing down the back applies pressure to that dimple in the centre and holds the movement in place.

    They would only serve to protect against dust when the back is off and the same would be true for magnetism.

    • Hi David,

      The movement sits absolutely firm without the cover, so I can’t really see how it holds the movement.

      Some watches have these made in a very thin metal, so thin that they can’t really be for holding the movement in place, e.g. on my Rado.

      Generally, watches with this sort of cover on the back are cleaner when they come in for a service.

      If the movement didn’t have the usual case clamps holding it, I would agree with you.

      Best regards,

      Christian

    • Hi David,

      Just checked the Omega parts catalogue, and it’s listed as a dust cover. Coming from the manufacturer, I hope that settles the discussion.
      I think you got mislead by the little dot on the back. Yes, the case back rests against that, but it holds the dust cover in place, not the hole movement.
      Also, the cover is of a softer metal than the case back, and has thus better antimagnetic properties than the stainless steel back. So that works with the case back in place.

      Best regards,

      Christian

  6. It looked generally pretty clean in there – was there any indication it had been serviced relatively recently, or is this just due to the well sealed case and dust-cover?

    I notice someone inscribed some numbers on the bottom plate – do they indicate anything useful or interesting?

    It looks good for its age – early 70s?

    • I think it’s just that the movement is pretty well sealed. Even without dirt coming in, movements dry out with time, plus there is always a bit of abrasion. You can check the movement serial number if you want the exact age – should be visible in one of the photos.

      The inscribed numbers didn’t make any sense to me…

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