3861 initial thoughts...

M M_pharmacist

Another question archer if you dont mind, during service, does 3861 require twisting movement to take off or put it back the balance wheel ? Is it also for 88xx movements which has a full balance bridges

Archer

Yes, all movements require this to some degree, but co-axial movements are quite different than a conventional lever escapement. The technique used to install the balance on a co-axial is the same across the range of them, so it doesn't matter what the movement is or if it has a balance bridge or balance cock.

M M_pharmacist

Much appreciated, I really love your answers and i want your opinion on newer omega calibers (8900 and 8800) and their derivatives, does these have fairly easy to service automatic modules? Does the rotor need a special tool and tricky to get it our ? I said this because there arent screws on the rotor unless if there inverted for cleaner look.

Archer

There is a big positive that I see in that both ends of the barrel arbor are now supported by jewels. Previously the barrel arbor just ran in a hole that was drilled directly into the brass “barrel and wheel train bridge”, and in a similar hole in the “hour recorder bridge”. This leads to wear and elongation of the hole over time, and when it gets bad enough it will allow tipping of the barrel inside the movement and loss of power. This often required the parts to be replaced (what Omega does at service) or for the holes to be repaired using bushings. In fact bushing the hole in the barrel and wheel train bridge is the most common repair I do on these watches, and I even see 1861’s with wear that requires repair, so it’s not just the really old watches that suffer from this. Here is an example of the wear often seen in the 861/1861 bridge:

Deafcon

In my personal experience with these movements, no. I’ve had 6 861/1861/1866 etc movements with very worn barrel arbor pivot holes in the 3/4 plate but no significant wear in the pivot hole that is part of the dial support.

Wear in 3/4 plate.

wear area repaired with a jewel.

The ratchet wheel and all the force exerted by winding is very close to the 3/4 plate hole that wears.

Y yyau

Hi Archer
Recently, because of your influence, I am very interested in the 861/186X. Regarding the self-made bush for main plate, I saw that you only shared on the main plate, how about bridge? Please check attached picture. I think both sides will be worn out. Is this true in actual experience?

Archer

So first a correction - the bushing I've shown is not in the main plate - in fact the barrel doesn't ride in the main plate at all. The only hole in the main plate that is really subject to routine wear is the center hole, where Omega installed a bushing in the 3861.

The bushing I showed is in the barrel and wheel train bridge.

As Joe has stated, the wear isn't common in the hour recorder bridge, and the reason is clearly shown in this photo you posted:



To the left of the red circle is the hour recording wheel. This meshes with the drive pinion that is on the mainspring barrel, so it shares part of the load with the barrel arbor. This helps prevent significant wear to the barrel arbor hole in the hour recorder bridge.

On the rare occasion when these do wear on an 861 or 1861 series, I typically replace them, because the 1861 hour recorder bridge is not expensive at all. In fact I often (with the owner's approval) replace the bridge on an 861 with one from an 1861. The 861 bridge in yellow or pink is 4.5 times the cost of the rhodium bridge for the 1861. Makes no sense, but most people are happy to save hundreds on a part that is under the dial.

On the 321, when this hole is worn, I do install a bushing - the hour recorder bridge is long discontinued, so there's not much choice there. Certainly a little more tricky that doing a bushing in the wheel train and barrel bridge, but not significantly so.

Cheer

Y yyau

Hi Archer
Thanks for your sharing
I have a curiosity, In 861/186X, if you use bush to fix it, is this method feasible? Because I see the two holes on the plate are very close

Archer

As I said, I replace the bridge, because it’s not common that it requires this. Can you install a bushing? Yes probably if you keep the wall thickness at a minimum.