Eterna Cal 135
Vintage Eterna Pocket Watch
Disassembly
Dirty & worn on the outside...
… & almost as dirty & worn on the inside
(“Dirty” is a word I could return to often for this watch)
The Eterna calibre 135 is not an especially high grade movement.
Likely more of a regular working man’s everyday timepiece.
Removing each hand from its pinion
And removing the dial from the movement
Dial Side of the Movement
Dial Washer & Hour Wheel
Cannon Pinion
The cannon pinion is friction fit to the minute pinion. Removing this now will allow the second wheel & minute pinion to be removed from the watchmaker side of the dial later on.
Watchmaker Side of the Movement
Trying to avoid overusing the word “Dirty”...
Balance Cock & Balance Wheel
The watch runs in its current state, but only just, & with no real hope of anything like accurate timekeeping.
Balance Complete
Balance Wheel & Hairspring
Balance Cock & Upper Balance Cap Jewel
The pivots that the balance staff turns on and the balance hairspring are indescribably fragile.
Best to remove the balance early on so as to get it out of the way of accidental damage.
Relatively unobstructed view of the pallet
Can see where the fork end of the pallet interacts with the balance wheel, & how the pallet stones interact with the escape wheel
Pallet & Pallet Bridge
This watch entered service around 1930 (& had a full long life, judging by the condition).
Parts of the winding mechanism overlap with
the going train (sequence of gears)
These need to come off ahead of the train
bridge in order for the wheels of the going
train to be removed.
Crown Wheel & Ratchet Wheel
The crown wheel core & the ratchet
wheel show signs of corrosion & pitting.
Screw heads don’t look so great, either.
Click & Click Spring
The click enables the ratchet action for the winding mechanism. This allows the mainspring to be wound via the crown & then prevents the mainspring from unwinding when the crown is released.
Train Bridge
I mostly work on wristwatches from the 1950’s & 60’s, but sometimes
it’s a good change of pace to take on an older pocket watch.
The Going Train
Can see how the mainspring barrel discharges power from the mainspring & turns the second wheel.
The second wheel turns the third wheel, the third wheel turns the fourth wheel, & the fourth wheel turns the escape wheel.
The frequency of oscillation of the balance wheel combined with all the gear ratios of the going train result in the fourth wheel making one revolution per minute & the second wheel making one revolution per hour.
The fourth wheel then directly turns the second hand via a long pinion that extends through to the dial side of the movement.
Second Wheel
Fourth Wheel
Third Wheel
Escape Wheel
Barrel Bridge
Can see that one of the screws is shorter than the other two.
I’ll make sure that this short one goes back in the same screw hole for reassembly.
Mainspring Barrel
Mainspring & Barrel Arbor
A fresher mainspring would expand & uncoil more than this one. This mainspring is showing its fatigue, but not much hope of sourcing a replacement.
Clutch Wheel, Winding Wheel, & Winding Stem
In a higher grade more refined calibre, you would often expect the stem, winding wheel, & clutch to remain captured by the mainplate in order to make life easier for the watchmaker. For the cal 135 these parts simply fall out once the barrel bridge is removed (just need three hands to put it all back together...).
Back to the dial side of the movement
'Keyless Works', the winding & time setting mechanism
(Although most of the winding mechanism fell out on its own
back on the watchmaker side)
Setting Lever Cap
Minute Wheel, Intermediate Setting Wheel,
Setting Wheel
Clutch Lever
Lower Balance Cap Jewel
The Lower Balance Hole Jewel is friction fit in to the mainplate & does not get removed
Ready for the cleaner
A relatively simple three-hand movement like this one doesn’t fill up very many cubbies in the parts tray
Two ultrasonic bath cycles with the cleaning solution followed by three cycles of rinse
The cleaning solution is specifically formulated to dissolve & remove watch oil lubricant, so it is critically important that no trace of the cleaning solution remains when the watch goes back together (don’t want any of the fresh lubricant to get compromised by residual cleaner left on any of the parts).
Reassembly
Main plate & lower balance cap jewel
Applying a very small measure of lubricant to the lower balance cap jewel prior to reassmbly
If the jewel is properly cleaned, & if the correct volume of oil is applied, then the surface tension of the oil drop will serve to hold the droplet in place while the watch in is operation, & ideally for years at a time.
Want to get the lower balance cap jewel installed without disturbing the oil drop
Putting the barrel bridge in place now in order to help hold the keyless works together back over on the dial side
Industrial automation & the advent of interchangeable parts that grew out of the late 1800’s Industrial Revolution resulted in pocket watches that, for the first time, could be mass produced at scale & as a commodity.
Setting lever
Clutch lever
Keyless works wheels
Setting Lever Cap
Clutch, Winding Pinion, & Stem
Done for now on the dial side
For the first time, a decent pocket watch came to be regarded as an everyday tool for
the regular working man, & not just as a status symbol for the landed gentry.
Reassembling the Going Train
That's starting to look better...
And the same Industrial Revolution that made the everyman’s pocket watch possible also then made it a requirement.
Factory shifts & train schedules running to +/- 15 minutes had become a thing of the past.
Train Bridge
Dial Foot Screw
Can see how the crescent of the dial foot screw will capture the dial foot. It's not a great system, as it necessarily deforms the shaft of the dial foot & often creates looseness in how the dial is secured. Most modern movements would use a more reliable method.
Going Train all back in place
Your typical pocket watch movement from this era would be generally considered to be basic & uncomplicated compared to many modern movements, but back in the day the mass produced pocket watch would have been look upon as a modern marvel.
Click & Click Spring
Crown Wheel & Ratchet Wheel
When the watch is being wound, the crown wheel necessarily turns counter-clockwise. In order prevent the crown wheel from unscrewing its own screw, the crown wheel screw uses a left-hand thread. This way the action of the crown wheel serves to hold the screw tight instead of loosening it.
Pallet & Pallet Bridge
If you look very closely, can see the tiny amount of lubricant applied to end facet of the pallet stones.
Balance in place, & back in action
Always get a good feeling of satisfaction & accomplishment to see an old movement come back to life.
But, that's only half the battle...
How's it making out on the TimeGrapher?...
... not great.
Losing more than 1min/day, but the
bigger problem is the 3.7ms of Beat Error.
What is 'Beat Error'?
When the mainspring is all the way unwound (no power), & there are no forces being transferred through the going train, & the balance wheel is at rest, then the movement is 'quiescent'.
In the quiescent state the balance is at rest & should be resting on center with respect to the pallet & the escape wheel.
If the balance wheel at rest is off center then when in operation this results in one direction of oscillation having greater amplitude than the other.
'The tick is longer than the tock'
3.7ms of beat error is big, & this needs to be adjusted before any finer regulation can take place.
The off center condition is hard to see in the flesh & hard to photograph, lots of hardware in between the viewer's line of sight with the pallet fork buried down under the balance.
When the balance is quiescent & on center, then the pallet fork will rest centered between the two banking pins. When properly adjusted then movement will then run 'In Beat'.
It's not easy to see, but looking closely you can observe how the pallet is being pulled over to the right by the balance wheel when at rest.
No mechanical watch can ever be adjusted 'perfectly', but in regulating a movement one of the first objectives is the try to adjust the beat error down the to the smallest possible margin. On a modern high grade calibre this should be down below 0.3ms, & lower is better.
For an old & well worn pocket watch movement like this, any beat error value under 1.0ms would be considered workable.
Any adjustment to the balance is an easy opportunity to cause damage.
Touching the hairspring is enough to bend it & ruin it, likewise for the balance staff pivots.
Balance comes back out...
Adjusting the Hairspring Collet
As with all things in watchmaking, the answer to the question, "How do I do X?", is always, "Well there's a special little tool for that...".
At the center of the coil the hairspring is attached to the collet. This is a split-ring collet, friction fit to the balance staff,
the small gold circle seen at the center of the coil.
The collet adjustment tool has a hole bored in the center which fits over the balance staff, & a little tooth to engage the gap in the split ring collet. This allows the hairspring collet to be rotated very slightly on the balance staff, & this repositioning of the collet (& hairspring) with respect to the rest of the balance wheel is what corrects for beat error.
Can see two black witness marks I made on the balance wheel (at about the 6 o'clock position) to help me judge how much I have moved the collet & hairspring.
Before adjustment
After adjustment, moved by about 1 - 2 degrees
And this has had mostly the desired effect
That very small adjustment to the hairspring collet has taken the beat error from 3.7ms to 0.9ms. Not perfect, but good enough to now allow for finer regulation once the reassembled movement has had the chance to pass through a few cycles of full-wind to full-discharge.
Reassembled
Timekeeping function is now restored, but there are still a few areas that look rough cosmetically.
The ratchet wheel & crown wheel core show pitting as an effect of corrosion, & many of the screw heads are scratched & scraped. Does not affect the timekeeping, but it would be nice to be able to lift the lid on the case back & have the movement look as good as it runs.
I can & I will take the roughest looking parts out & apply a polish, but to take it a step further I will also apply Heat Bluing to some of these parts. Heat bluing started out as a form of corrosion resistance, but done right will also add some pleasing decoration to the finished movement.
First step is to apply a mirror polish
Followed by a thorough cleaning with alcohol to remove all trace of the polishing compound
Then apply heat until the desired thickness of oxide layer forms
And if everything goes right, you then get a rich blue effect on the finished part.
Not from pigment, though, the oxide layer is perfectly clear. The blue effect is a result of thin film interference.
Check out the Journal section for a more in depth look at the Heat Bluing process.
And there it is
Dressed up quite a bit finer now than the day it left the factory
Completion
