c4.1.4 Day Date Calendar – AS 2064/2066

In Level 4, Watch Repair Course by Mark Lovick1 Comment

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Lesson Transcript

Before we close this chapter on calendar mechanisms I feel it would be good to cover the AS 2064 or 2066 caliber movement which has a day and date display. But the operation of this mechanism is slightly different from the gradual pushover of the calendar wheel by the driver, where the date disk is usually driven first, followed by the day disk.

This particular calendar facilitates driving both day and date disks at the same time and with an immediate changeover rather than being a gradual changeover which may sometimes take place over many minutes.

This system was integrated with several different models such as the 2061 and 2063 which only had date recording. But was also found in others such as this AS 1913.

Now this particular AS2066 is one of my scrap movements and is a little damaged. But disappointingly the setting lever spring does have a fracture and therefore I cannot demonstrate the rapid calendar change, but nevertheless, I wanted to present this mechanism to you as it was quite a popular movement found in many models of watch. And the chances are very probable that you will come across one of these sooner or later.

Incidentally, parts for this movement and others of this era have not been manufactured for many years and are quite obsolete as a result. A quick look on the popular watch material supplier Cousinsuk.com shows as much. Although a quick search on eBay and I have found a setting lever spring, albeit very expensive.

But lets take this calendar apart and see how it works.

And first of all I remove the day disk and as can commonly be found there is a star disk under the disk to allow the disk to jump into position.

And here is the day jumper spring which causes that to happen, it is secured under the cover plate here.

I will point out the day corrector and it’s spring. When the crown is turned, a pinion with a finger attached is rotated and will nudge the day corrector causing it to forward the date and day disks by one increment.

You may observe that the hour wheel has an extra layer of teeth to drive the calendar driving wheel. And the calendar driving wheel has a finger mounted to it which causes the day disk to turn. If the hands are turned backwards the finger will ratchet over the day disk teeth with the help of a spring.

Secured to the underside the calender driving wheel there is a cam which operates a yoke which is currently hiding under the cover plate. The yoke is causes the date disk to snap over and is kept under tension by this spring.

And this system allows the date disk to snap over immediately at the same time as the day disk rather than a gradual changeover. It’s a very nice piece of engineering.

So now I will take this apart further so we can take a look at all the components.

First I will remove the day corrector and it’s spring… The day corrector has a post which is elevated downwards over the setting lever spring.

The calendar cover plate is now only held down by one screw once the day corrector has been removed. But be careful about removing this screw. The calendar jumper and it’s spring are quite strong and once this screw is loosened will become unstable. In fact, the spring will cause the jumper to push the date disk over to one side and without being careful there is a strong risk of the spring and possibly the jumper flying across your work area.

So we are going to hold the cover plate steady as the screw is loosened and removed. And then with slight downwards pressure of your pegwood we can lift the cover plate on the opposite side. Notice how everything shifts due to tension of the jumper spring being released.

Everything is still very unstable until the tension is completely released though so we are going to very carefully lift the cover plate away and this exposes the jumper and spring. I’m going to hold the spring with my pegwood whilst gently releasing the spring from it’s position with my tweezers. And then I can remove the jumper.

The day jumper can be easily lifted away at this stage. As can the date disk.

Now let’s have a closer look at the under side of the driving wheel. Here you can observe the mounted cam.

As the driver turns this cam causes the yoke to shift it’s position and tension builds up as it presses against the yoke spring. Until the cam turns to the point where there is a drop off and the yoke is caused to snap back to it’s home position turning the date disk by one increment as it does so.

Here I use my pegwood to hold the yoke in position before unscrewing the yoke spring and releasing it’s tension.

So that’s the calendar mechanism of which variations can be found in many manual and automatic AS movements, which were very popular with many different watch brands.

We will put this together in a moment, but before we do, I want to point out an unrelated feature of this movement which will be important for you to know should you work on one of these models.

I will start by removing this cover plate which is holding down the minute wheel and what seems to be a cannon pinion.
But the first thing you may notice is that the cannon pinion here is actually free running, it simply slides on and off the post with zero friction.

Now normally this would be a concern but this is quite normal with this movement and others in it’s family.

The minute wheel is also slightly different from the norm in that it has a post and is fitted to a hole in the main plate and held under a small amount of tension with this spring.

But the friction which allows the motion work to function as expected is actually provided by the one of the train wheels called the Great Wheel. This Great Wheel, which is driven directly by the barrel, has an additional pinion and spring mounted to it’s arbor and this provides the required friction for the motion work.

I will quickly take this watch apart so that I can show you this in more detail…

So here is the Great Wheel and you will notice there are two pinions. One is actually part of the wheel arbor and the other is a separate component held in place with a tension spring. This pinion directly drives the motion works via the minute wheel.

When servicing this I find it useful to use a balance roller remover such as this Bergeon Bradux tool.

I place the jaws of the Bradux tool between the fixed and free pinions and very gently squeeze until the spring releases and it usually comes off very easily. Before you do this, take note that this spring is fitted with the flat side down. If you attempt to refit this spring upside down it will not snap into place.

I will show you how to re-assemble the great wheel using a standard staking set.

I will use a flat holed punch.

And I will choose an appropriate sized hole on the stake to receive the wheel pivot, using my center punch to position the table.

Now I can place the pinion into position and press the spring into place.

And now I can re-assemble.

Getting back to the subject of this lesson, to re-assemble the calendar, I first place the hour wheel.

And the yoke.

Place the spring into position but don’t tension it against the yoke yet. First, partially screw it in place. Then position the spring against the yoke. And now tighten the screw.
I can now replace the driving wheel.

And place the date disk into position

Now for the jumper and spring which can be tricky.

I first place the jumper and push it over to one side and you can notice the date disk is pressed over too far as a result, that’s fine for now.

And I can place the day jumper into position.

And now I want to place the date jumper spring. I loosely place it in it’s position and then I hold it secure with my pegwood. Whilst holding the spring with my pegwood I can use my tweezers to manipulate the spring against the jumper.

Now I can replace the cover plate with the jumper side going down first. Ensuring the screw holes are lined up I can hold the cover plate gently secure with my pegwood and with my tweezers I can slide the date disk into it’s true position. The slight pressure from my pegwood is effectively securing the jumper and spring at this stage.

And now I can secure the cover plate.

And finally I can replace the rapid day change components.

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Matthew Croxford
8 months ago

That pesky jumper spring is very excitable.