Now we were a bit more familiar with the 6498 we could start to learn how to service everything correctly. The movement minus the balance would be broken down into different areas. We would focus on one area at a time, learning how to find faults and how to correctly lubricate all the components.
We started with the keyless work, first learning of the common areas that wear can occur and then tasked with finding some of these faults that have been deliberately replicated by our tutor. The keyless work allows the movement to be wound when the crown is in the first position and the time to be set when the crown is pulled out to the second position. The various parts coupled with the winding stem allow you to change between the two.
We were shown where to look for damage when inspecting the parts, particular attention is payed to any friction points where wear and tear is more likely to occur. These friction points are lubricated with either oil or grease but over time this can dry up and leave metal on metal contact. This type of wear is more of a problem in vintage watches or older watches that have not been serviced in there lifetime but is still important to look out for.
I thought it would be useful to detail each part of the keyless work and go through what sort of things to look out for during inspection. I have used pictures from the ETA technical guide that show the parts numbers and later on in this post you will see where they are located on the main plate.
The edge of the yoke must be checked for any wear or damage, particularly on its two main contact areas with the yoke spring and setting lever. These areas are the top right corner in the picture and the central point of the bottom face. Its also important to check the post on the main plate that holds the yoke for damage or wear. The yoke spring must be checked for flatness as this not only affects its function but also makes it impossible to put into position on the main plate.
The setting and intermediate setting wheel teeth must be checked for any damage as this can affect there engagement with each other, the motion work and the sliding pinion. Once again its important to check the posts on the main plate that hold these wheels for any damage or wear.
The Breguet teeth on both the sliding and winding pinion must be checked because any damage can stop them correctly engaging in the hand setting position. The contrate teeth on the sliding pinion must also be checked as any damage or wear can stop it engaging with the intermediate setting wheel. Finally the teeth on the winding pinion must be checked because they engage with the crown wheel to wind the movement.
The winding stem has a number of areas that must be checked these include the pivot, the square and the slot. The pivot must be straight and have a burnished finish, any damage or wear will case the pivot to wear away the hole in the main plate it sits in. The square sits inside the sliding pinion so any burrs or other damage can also damage the sliding pinion. The slot holds the setting lever post and any wear can stop the watch moving correctly from the winding position to the setting position.
The setting lever post that engages in the winding stem slot and the post that engages with the setting lever jumper are inspected to check they are free from damage such as chips or burrs. Finally the setting lever jumper is checked for flatness and the slots that accommodate the setting lever post are checked for damage, both faults can cause problems with the watch changing between winding and hand setting.
We could now move on to learning about lubrication, there are a number of different lubricants that can be used depending on the manufacturers specifications. These include HP1300 (Oil), MR4 (Grease) and Molicote (Grease), personally I prefer HP1300 as in my experience it can be applied more sparingly and is less prone to attaching itself to areas you don’t want it to be.
We spent a few days working on correctly lubricating the keyless work and identifying damaged parts before we were ready to move on to the next part of the movement. Finally I was on the way to learning how to complete a full mechanical service, I felt confident that I could now assemble and lubricate the keyless work to a high standard in a short amount of time without any problems.