Service: Longines Dress Watch with Longines 12.68Z Movement

 In Watchmaking

This Longines is part of my collection. It’s a 1956 watch, but it’s still in excellent condition with a little patina on the dial.

The movement is the Longines 12.68Z with serial number 9.49xxxx. On April 28th, 1956, Longines sold it to Bessire which was their Belgian agent at the time.

It didn’t have any problems, and it kept good time. This is just a regular service to keep it in pristine condition. In the case of Longines, it’s extra important because parts are hard to find and they’re expensive.

Disassembly

As always, remove all power from the mainspring before you start working on the movement. This is to prevent damaging the escapement while working on the wheel train.

Move the click away from the ratchet wheel while slowly letting the crown slip between your thumb and index finger.

In this movement, you can move the click with a ped wood, cocktail stick, or toothpick because of its shape.

Remove the balance and the pallet fork with the pallet cock and store them somewhere safe.

Longines 12.68z

The balance, pallet fork, and the pallet cock removed.

Lift the cannon pinion on the other side of the movement.

The center wheel is underneath the ratchet wheel, so I lift both the crown wheel and the ratchet wheel first. The crown wheel screw is left-handed although it doesn’t have the three grooves.

Longines 12.68z

The ratchet wheel and the crown wheel removed.

The escape wheel bridge and the wheel-train bridge are separate parts. Lift the escape wheel bridge and then the wheel-train bridge to get access to the wheel train.

Lift the escape wheel, the fourth wheel, the third wheel, and then the center wheel.

Longines 12.68z

The escape wheel bridge, wheel-train bridge, and the wheel train removed.

Remove the barrel bridge and lift the barrel.

Longines 12.68z

The top plate empty apart from the set lever screw.

Turn the movement around to work on the bottom plate.

Remove the motion work and the keyless works. Don’t forget to lift the bottom balance end piece.

Pre-clean all the parts with a peg wood and then clean them in the watch cleaning machine.

Assembly

Start with the bottom balance end piece. Don’t forget to lubricate it with a tiny bit of 9010.

Fit the set lever with the set lever screw.

Place the barrel in position and fit the escape wheel, the fourth wheel, the third wheel, and the center wheel. Lubricate the center wheel post with some HP1300 just before you install it.

Install the escape wheel bridge and then the wheel-train bridge. Keep testing the wheels while you position all the pinions in their bearing jewels.

Longines 12.68z

Barrel, the wheel train, the escape wheel bridge, and the wheel-train bridge installed.

Install the barrel bridge, the crown wheel, and the ratchet wheel. Lubricate the crown wheel boss with some HP1300.

Longines 12.68z

The barrel bridge, ratchet wheel, and crown wheel installed. If you’re very perceptive, you’ll notice that I took the picture before I fitted the screws.

Turn the movement around and fit the motion works and the keyless works. Lubricate the third wheel with some 9010 before you place the minute wheel in position.

It’s worth mentioning that the return bar and the return spring are one part in this movement.

Longines 12.68z

The bottom plate completely reassembled apart from the hour wheel.

Don’t forget to lubricate the bearing jewels for the escape wheel and the fourth wheel with some 9010 and flip the movement to the top plate.

Lubricate the exit stone of the pallet fork with some 9415 and reinstall the pallets with the pallet cock.

Give the crown a few spins and test if the pallet fork snaps to the next position with the lightest touch. If it does, the movement should immediately start running when you place the balance in position.

Place the hour wheel and a dial washer in position and fit the dial.

This watch is a front-loader with a removable bezel, so I like to fit the movement/dial, the crown, and the bezel first. Then, install the hands and make sure there is enough clearance between the hour hand and the dial and between the hour hand and the minute hand.

Finally, polish the crystal and reinstall it.

Longines 12.68Z

What do you think of vintage Longines watches? Do you have a similar one? Let me know in the comments below.

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