ETA 6498- The Barrel and Mainspring- Adjusting End Shake & Lubrication

The next part of the 6498 to learn about were the Barrel and the Mainspring. The Mainspring, in combination with the Barrel and Barrel Arbor, provides the power source needed for a watch to run. Our learning focused on how to adjust Barrel end shake, how to wind Mainsprings, how to correctly lubricate and how to put everything together. After being shown the common areas to look for faults, the faults were deliberately replicated by our tutor for us to identify and then rectify.

Our first challenge was to remove the mainspring from the Barrel, this is not an easy task especially when you see how long an unwound Mainspring is and how small the Barrel it fits into is. The spring is under a lot of tension so its best to approach this process with caution the first few times until you have learnt the correct technique.

To remove the Mainspring, the Barrel is placed with the Cover facing upwards and then pressure is applied to each side of the Cover to pop it open, the Cover can then be removed. The next step is to remove the Barrel Arbor which is situated in the centre of the Barrel and hooked into the Mainspring. Care must taken at this point because pulling the Arbor straight up and out will send the Mainspring flying through the air! There are a few different ways of removing the Arbor but both use the same method of twisting the Arbor to disengage the hook from the Mainspring and then lifting it out. The Mainspring can now be removed, this to begin with is the trickiest part of the whole process and requires the right technique. One mistake and the Mainspring will fire itself into the air before tangling itself up in what we call a ‘Bird’s Nest’. The key is to cover the edge of the spring and remove it slowly from the centre, rotating the Barrel with the spring as it comes out.

With everything disassembled, we could now learn where to look for signs of damage or wear on the Barrel, Barrel Cover, Barrel Arbor and Mainspring. We started by looking at the Barrel Drum and Barrel Cover, the main things to check are the teeth on the Barrel Drum and the hole in the Barrel Cover. Broken teeth on the Barrel Drum would stop it correctly engaging with the centre wheel pinion and release unstable power through the gear train. Wear or damage around the hole in the Barrel Cover can increase side shake, this can cause the Barrel to rub on the main plate or barrel bridge and affect power delivery which in turn has a negative effect on timekeeping.

Barrel Drum & Barrel Cover…

The Barrel Arbor Hook must be checked for damage as this can cause slip between the Arbor and the Mainspring, preventing winding and potentially the watch from running. The Arbor pivots at each end sit in un-jewelled holes in the main plate and barrel bridge so can be prone to wear. Any damage can increase friction, effecting timekeeping and potentially causing wear to the pivot hole in either the barrel bridge or main plate.

Barrel Arbor…

The Mainspring has a few areas that are important to check, the eye that allows the Barrel Arbor Hook to engage with the spring and the Bridle that holds the spring against the Barrel wall, allowing it to be wound. Any damage to the Eye can allow the mainspring to just slip around the Arbor. A damaged Bridle can prevent the watch from being wound fully wound, if it slips around the barrel wall before the spring is fully wound, the power reserve of the watch will be effected.


Having taken it all apart and discovered where to look for faults, it was time to learn how to put it all back together and lubricate it correctly. I will go through reassembly and lubrication in order, not forgetting the other important thing for us to learn, Barrel end shake. The first step is to clean and lubricate the Mainspring using felt tweezers containing the lubrication, with this completed its time to get to grips with the Mainspring winders.

Its important to select the correct size of Mainspring winder, the winder must fit inside the Barrel Drum, to ensure the spring when fully wound can be released inside the drum. If the winder is too large it wouldn’t be possible to release the spring into the drum and if too small it wouldn’t be possible to fully wind up the spring.

Mainspring Winders…

The Mainspring winders have a hook similar to the one on the Barrel Arbor that engages with the eye on the mainspring, allowing the spring to be wound up. The hook is engaged with the eye and then the two components of the winder are put together to allow the spring to be wound. The spring is wound in until the Bridle catches on the outside of the winder, the Bridle is then pushed inside and now the whole spring is fully wound inside the winder. The cap of the winder with the Arbor hook must now be removed, in order to do this the winder is wound in the opposite direction and gently lifted at the same time. This method allows the hook to be disengaged without pulling out the Mainspring.

Mainspring Wound Up…

Close Up…

The Mainspring is now ready to be released into the Barrel Drum, this done by placing the winder inside the drum and then pressing the release button. The Mainspring is now in position and ready for the Barrel Arbor to be inserted. The Barrel Closer that I made at the start of the year was about to prove its worth.

Ready for the Arbor…

Close Up…

The next step is to lubricate the Barrel Arbor in preparation for fitting it into the Mainspring and Barrel Drum. The lubrication and fitting can be done using a pair of tweezers but if available its easier to use a Bergeon Barrel Arbor Holder. The Barrel Arbor Holder makes it slightly easier to apply the lubrication but more importantly it makes fitting the Arbor into the Mainspring a whole lot easier.

Bergeon Barrel Arbor Holder…

I like to lubricate the Barrel Arbor using HP 1300 as I find it easier to apply neatly compared to the recommended Moebius D5 grease. The points of lubrication are the two smaller steps shown in the picture below, the Barrel Bridge and Main plate are lubricated in order to apply lubrication around the pivoting points.

Arbor Lubricated…

The Arbor can now be inserted into the Mainspring and Barrel Drum, once located it must be twisted until the Arbor Hook engages with the Eye on the Mainspring. This can be done with tweezers but its sometimes difficult to twist the Arbor to engage with the Mainspring Eye without slipping, using the Arbor Holder tool makes this process stress free.

Ready for the Barrel to be closed…

The last job is to fit the Barrel Cover and check the End Shake, Barrel End Shake is really important and must be set correctly. Too much End Shake can cause the Barrel twist under the tension of the Mainspring and then stop its teeth from meshing with the centre wheel. No End shake at all can cause the Barrel to push down on the Mainspring potentially causing the watch to stop.

To fit the Barrel Cover, the Barrel is put in position on the Barrel Closer and the Cover placed on top, now the Barrel Closer lid can be fitted and pressure applied. There will be a clicking sound and the Cover is now fitted. The End Shake is now check between a pair of bronze tweezers. If adjustment is needed,now is the time to do it. Too much End Shake can be rectified by removing the Cover and placing it on the base of the Barrel Closer, a sharp piece of peg wood is placed into the hole and downward pressure applied to slightly bend the Cover. No End Shake or too little can be corrected by applying pressure to the sides of the Cover while still fitted to the Drum. This process is the same used for removing the Cover but with less applied pressure.

The whole process of servicing the Barrel seems relatively complex but in reality, after lots of practice, this process takes a matter of minutes. Obviously the 6498 has a rather large Barrel so working on smaller calibre’s with smaller Barrels can make things a little more tricky. With two areas of the movement now covered, we could progress to another part and I was really looking forward to the next challenge.

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