A labour of love: Sicura Chronograph / EB 8420-74

We quite often have watches in the workshop that don’t have a lot of commercial value, but have great sentimental value to our customers.
This Sicura is certainly one of those.

The repair bill will be quite a bit higher than the value of the watch is, but if the watch belonged to a late loved one, who cares?

Inside lurks the EB 8420-74, made by Ebauches Bettlach. This is the cheapest chronograph movement that was around at the time, with pin pallets and a big spring on top instead of a cock or a bridge.

There were two versions of this movement – the 8420-74 is the luxury version with 17 jewels (used in this watch), and the 8420 was the 1 jewel version, and even cheaper. Funnily enough, Heuer used these in their extremely funky “Easy Rider” plastic case series of Chronographs. I’ve done one of these years ago if you want to follow the link.

The dial is very nice, and I like the colours.

The watch ended up in our workshop because setting is very erratic, and the crown often slips. The culprit is here – the intermediate setting wheel, driven by the sliding pinion, has a worn pivot. The pivot is unfortunately part of the base plate, so I will have to get a bit inventive here.

A view of the chronograph wheels. From left to right: minute recorder, minute recorder driving wheel, central second recorder, chronograph clutch wheel, wheel over fourth wheel to drive the chronograph.

The pin pallet fork.

The wheel on the underside of the barrel drives the cannon pinion directly, but the clutch sits between the barrel and the wheel on the underside of the barrel, which is quite unusual. Second and third wheel of the gear train at the bottom left of the barrel.

The keyless works. Again, cost was the main driver in the construction, but it works. The intermediate wheel is just about visible by one tooth below the winding stem. It drives the wheel under the barrel directly to set the time.

I remove the old pivot, and drill a guiding hole into the middle of the plate where the intermediate wheel sits.

Now I turn a new post for the wheel on the lathe.

New post for the intermediate wheel

Intermediate wheel with new post.

I’m about 2/100 out of the centre, but hopefully, the repair will work.

I put the base movement together to see how it performs.

For a pin-pallet movement, the performance is actually quite good. Positional variation is not so hot, but you only have to look at the execution of the balance to know why.

Unfortunately, the repair doesn’t work, and the new post comes loose. A plate for the 8420 movement is available, but that’s the 1 jewel version, and I’m sure that that won’t just fit the parts that I have here in front of me.

The new plate doesn’t have the little post (at the top middle of the photo) for the setting lever, and it also has a fixed post instead of a threaded post for the setting lever spring. This will need some changing parts around in the staking set.

The two parts are pressed into the new plate, and assembly can begin.

The movement is back together, and the chronograph is working.

Now the date wheel and its mechanism goes in.

But I’m not done yet… when removing the second hand when taking apart the watch, the tube of the hand stuck on the second recorder, and the hand broke off from the tube. As the top of the tube is a bit mangled, I can’t just stick the hand back on.

So it’s off into the lathe to turn off the top a tiny bit (the tube has an outside diameter of 0.45mm!).

Now I can put the hand back on.

To make sure that the tube won’t come off again, I solder it to the hand.

Now the hands go on, and I can case the movement.

Not a bad looking watch, and a chronograph with a date! The minute recorder only does 15 minutes, but hey, this watch wasn’t expensive when it was new. The kind of watch I was drooling over when I was a boy of 12 😉

Just in case you are wondering, the buttons work as follows: The lower button is for starting and stopping, and the upper button for the reset. There are some special features: You can reset the watch directly when the chronograph is running, but this is not a flyback. The chronograph will reset and stay at 0 if you do that. Also, you can only start and stop with the bottom button once. There is no restarting it, and it has to be reset to re-start it.

I quite like working on watches like this, mainly because I know that without me taking on the work, there would be very little chance that this watch would ever work again properly. Very few people take on cheap watches for repair, and there are good reasons for that. In the time that it took me to get this one going again, I could have serviced 4 standard automatic date watches … So I only do this sort of stuff once or twice a month, as I have children to feed.

5 thoughts on “A labour of love: Sicura Chronograph / EB 8420-74

  1. good day to you i have a sears EB8420 WITH NO CALANDER
    i would like to have it serveced when winding it up it sean to have a broken tooth in winding but does work but does not keep good time can some let me now who could service and the price
    thank you

  2. Im so tired of seeing these on Ebay describes as Sicura Breitlings and I am often gobsmacked at the prices they reach when sellers employ this skewed historical connection.
    However, Sicura made great looking watches, some design classics albeit a little crappy ‘under the hood’.

    Turning the Second Hand tube was masterful and you deserve every penny!

  3. Hi
    An Interesting Read.
    I too have the same watch, with the same problem.
    A slipping crown when setting and adjusting the hands.
    The watch runs well and the chrono function is good.
    Are you able to recommend a Watchmaker that can take a look at mine ?
    Many Thanks
    Mark Simpson

  4. It’s great that you are restoring some of these “cheap” pre-quartz era watches. They are historically interesting even if their horological contribution can be debated 😉

    • I agree totally. There is a whole era or class of engineering, including but not exclusive watches which is disappearing because it is not viewed as classic.

      As time permits, keep a small space for tasks like these! 🙂

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