This week an Eterna dress watch that’s part of a batch from Poland.
The movement is the Eterna 520U with 15 jewels and a hidden ratchet wheel and crown wheel. It’s Eterna’s first caliber for gent’s watches. The serial number dates this watch to 1952.
This watch did run, but it was a mystery when it was last serviced. The crown was bent, and the crown action between the two positions was sluggish.
Disassembly
As always, it’s important to remove all power from the mainspring. Because of the design, the click is located underneath the barrel bridge so you’ll have to reach through the hole with a cocktail stick or a watchmaker’s pick to move the click away from the ratchet wheel.
Slowly let the crown slip between your thumb and index finger, or you may damage the mainspring.
Remove the balance and the pallet fork with the pallet cock and store them somewhere away from harm and dust.
Turn the movement around and lift the cannon pinion.
The escape wheel bridge and the wheel-train bridge are two separate parts in this particular watch. Lift both to gain access to the wheel train.
At this point, it’s difficult to lift the center wheel because it’s underneath the barrel bridge and the ratchet wheel. The safest way is to begin with the center wheel because then you can lift the wheels straight up without having to wiggle them from underneath the next wheel.
The barrel bridge is divided into two separate parts as well. One for the ratchet wheel and the click and one for the crown wheel. Remove both so you can lift the wheel train, starting with the center wheel.
Remove the barrel to complete the top plate.
Flip the movement around to start with the bottom plate.
As you can see, the set lever spring is broken. The broken part is in between the cover plate and the return bar spring. This caused the sluggish feeling of the crown between the positions. I ordered a new one.
Remove the set lever spring (and the broken part) and lift the minute wheel, the setting wheel, and the intermediate wheel. Then, lift the return bar spring and the return bar.
Flip the movement around to remove the set lever screw and lift the set lever from the bottom plate.
Pre-clean as much as you can with some peg wood. The bearing jewels, the pallet stones, and the pallet fork crown need some extra attention.
Clean all the parts in the watch cleaning machine.
Assembly
Always begin with the set lever and its screw. It’s a fiddly job, so it’s easier without any extra parts installed.
Fit the barrel. Place the escape wheel, fourth wheel, third wheel, and center wheel in position.
Reinstall the escape wheel bridge and the wheel-train bridge. Make sure to keep testing the wheel train while you’re installing these bridges. Everything should spin freely.
Reassemble both barrel bridge parts. Place the one with the crown wheel in position and screw it down.
Install the ratchet wheel on top of the barrel arbor and place the barrel bridge part over it. You’ll need to wiggle the ratchet wheel because the click and the crown wheel have to fall into place.
Turn the movement around to begin work on the bottom plate.
Place the clutch wheel and the winding pinion in position and install the winding stem. Fit the return bar and the return spring, the setting wheel, and the intermediate wheel. Make sure that the setting wheel has the rounded part at the bottom.
Lubricate the bearing jewel for the third wheel and fit the minute wheel.
Place the (new) set lever spring in position and screw it down.
Turn the movement around to install the pallet fork and the pallet cock. Test the wheel train by giving the crown a few turns. The pallet fork should snap to the other position with the lightest touch.
Install the balance and if it doesn’t start to move on its own, give the movement holder with the movement a small flick.
Now, it’s time to clean the shock protection system which is the Eterna-U device in this case. This is almost the same as with an Incabloc.
Unhook the spring and lift the endpiece and the jewel hole. Clean them with Onedip or similar, lubricate them, and reinstall them.
Fit the hour wheel and the washer and fit the dial and the hands. Blow the dial and the inside of the crystal clean with the dust blower.
I always place a lint-free tissue for watchmakers on top of the casing cushion and place the movement with the dial on top of that. Slide the case with the crystal over the dial and the movement and carefully turn everything upside down while holding the case and the casing cushion. Now you can reinstall the winding stem and secure the casing screws.
What do you think of this Eterna? Do you have one in your collection? Let me know in the comments below.
