Reassembly: Omega Bumper 351

Time to do some cleaning and to reassemble Dom’s Omega…. The parts are sitting in rinsing solution to remove the cleaning solution.


Every part is dried and inspected – here, I’m checking the jewels on the top plate. If there is any dirt left, I clean the jewels with a sharpened pegwood stick and put the plate back into the alcohol to rinse the dirt off.

When the parts are inspected, I put them on a sheet of kitchen towel so any trapped alcohol can evaporate to completely dry the part.

I clean the case with a pegwood stick and lightly polish it with a polishing cloth. As it’s gold filled, I can only carefully polish as I don’t want to remove the gold layer.

All the parts are nicely lined up (apart from the ones that can’t take cleaning fluid, such as the pallet fork, the dial, etc.

The pallet fork is cleaned with some rodico. For any dirt that won’t come off this way, I use a pegwood stick, but this pallet fork is pretty clean.

The underside of the cleaned pallet fork – as most manufacturers, Omega only polished the visible side of the fork.

Under the microscope, it’s hard to get the light right to see some reflection on the polished surface, but this is the polished upper side of the fork.

Here is the escapement wheel, with the focus on the pinion. No real wear in all those years.

Again, we are looking at a wheel that is probably over 60 years old, and probably has been turning for most of that time. Pretty much as good as new.

Once everything is cleaned, the parts go into a plastic container with an airtight lid awaiting the arrival of the parts. Make sure all rinsing fluid has evaporated before sealing! (That’s why I spread the parts out on a sheet of kitchen towel before packing them).

The dial as usual wrapped in a sheet of watch paper. You can’t be too careful with a dial!

New main springs come pre-wound, held by a ring (the one at the bottom left). Just to show you the difference between the old and the new spring, I unwind it.

The new spring is wound into the barrel.

With the barrel closed, I start reassembling the top plate and start with the barrel and the barrel bridge.

Next, I put in the wheels of the wheel train.

Now I carefully place the wheel bridge and nudge the wheel pivots into the jewels. Before putting the bridge screws in, I test that all the wheels turn freely. Once the wheel bridge is fixed, I oil the jewels. I use Moebius 9020 for the centre and third wheel, and 9010 for the fourth and escapement wheel.

Now I press the wheel that drives the second hand arbor onto the third wheel pivot.

Then I mount the tiny little bridge that holds the second pivot in place, and the pallet fork and pallet fork bridge.

As I want to wind the watch before putting the balance wheel in, I turn around the movement and assemble the bottom plate. I start off by putting grease into the opening for the castle and crown wheel.

Then I assemble the bottom plate.

I wind the movement, and turn it around again. After oiling the balance jewels, I put the balance assembly in and the watch starts ticking immediately.

Then the bridge with the jewel for the second hand pivot goes in. I love that copper electroplated finish.

The final parts of the bottom plate assembly go in, and I’m ready to put the dial back on.

The back side of the dial has a serial number.

Not much I can do for the dial but giving it a brush.

The hands get a polish by wiping them over a polishing cloth.

The hands are on, and I can case the movement.

The new crystal goes into the bezel.

That looks better!

Now the hammer and ratchet for the auto winder are mounted.

I like the end result. Still has a visible history, but it’s nice and tidy.

The timegrapher shows me an amplitude of 250 and a beat error of 0.2. I will do a final adjustment after letting it run for day on my bench.

Saturday, April 21st, 2012

That’s what I call a result… Compare the amplitude with the 194 degrees the watch had when I received it. Great beat error of 0.1, and set slightly fast in dial up position.

Two more days on my bench, and I’m ready to ship.

10 thoughts on “Reassembly: Omega Bumper 351

  1. How are you adjusting the beat error of this watch? Are there any special trick /attention needed when you take out the automatic?

  2. Dear Christian,
    when seeing the parts that cannot take cleaning fluid I always wondered why the balance isn’t among those. You have described in some posts why you leave it in its place when cleaning the parts (after taking out the cap jewels), so it seems not to be overly damageable in that respect. But why is this so, isn’t the impulse pin fixed with shellac just as the pallet jewels are? Thx and
    kind regards

  3. Hi, Nice result! Can you please tell me how you put the main spring in the box? I’m not used to these springs and I don’t know how to put it in again.

    Thanks in advance.

  4. I bought the twin to this thing literally the day before yesterday! Right down to the little bit of patina on the face! Its is so cool to see it torn down and rebuilt THANKS!

    My education for this month is complete!

  5. Christian-
    I just received the watch back today. Fantastic job!!! Considering what you started with I’m amazed at how it looks. And to think that I initially questioned the merits of doing business from “across the pond”. You made the process fun and informative. I’ll be back! Thanks.
    Dom (aka Bumper 351 Guy)

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