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very watch can present a new and different challenge to your watchmaking, skill set. This month I service a

manual-wind Jaeger-LeCoultre ( JLC) wristwatch.As a watchmaker I am never bored at the workbench;

there is so much variety out there when it comes to movement designs, with each new design having something to offer in terms of experience and knowledge. This is the first time I have had this type of JLC movement show up on the bench, and I was looking forward to tearing it down.

My first impression was that this JLC had seen better days, at least as far as the dial and hands were concerned, Figure 1. More times than not the O-rings on the crown are overlooked during servicing and after a number of years they simply dry up and stop working. It looks as if this crown O-ring stopped doing its job some time ago, allowing moisture to penetrate the case, with the dial taking the brunt of the damage; I hoped the movement hadn’t suffered the same fate. Removing the case back revealed a very nice condition manual-wind movement, with no visible damage, equipped with indirect drive centre seconds, Figure 2. Many older movements with centre seconds have this configuration, with a wheel pressed on to the extended arbor of the fourth wheel, driving a pinion fitted through a hollow centre arbor. One thing to be aware of with this design is that the seconds hand tends to be ‘ jumpy’, especially when compared with the more modern layout where the fourth (seconds-drive) wheel sits in the centre of the movement driving the hand directly. One reason for the jerkiness is the train’s relatively slow beat magnified by the length of the centre seconds hand. The main reason, though, is because of the backlash between the supplementary driving

Robert Horan MBHI

Servicing a Jaeger-LeCoultre Manual-Wind WristwatchHints and Tips for Servicing a Good Quality Movement

wheel and the centre seconds pinion. In this arrangement, there is no permanent torque applied between this pair of mobiles and the leaves of the pinion are free to f loat between the teeth of the wheel. To overcome this, there is a tension spring which is designed to apply a permanent bias to the centre seconds pinion. It’s meant to absorb all the slop in the system, but this arrangement is always prone to problems, because the spring’s precise tension, and therefore the jerkiness of the hand, is the result of judicious bending, tweaking and manipulating, all relying on the judgement of the watchmaker rather than on a definite mechanical outcome. Even when correctly set, the spring’s frictional rubbing can drop the balance amplitude.

This also gives problems when re-mounting the seconds hand, which I refer to later on. A much better arrangement is to have the centre seconds drive ‘in the train’, not as a side branch. With the fourth wheel planted in the centre of the movement, modern calibres have done away with the problem of the jumpy seconds hand, with its tendency to be unpredictable depending on the position of the watch.

Why do I mention this? Because on a few occasions I have had negative feedback from clients after servicing this type of movement, their complaint being that the seconds hand was ‘still’ jumpy even though I had just serviced the watch. They fully expected the servicing to smooth and completely eliminate the jumpy seconds hand, which isn't always possible.

As is typical with this design, the indirect sweep seconds drive wheel is pressed on to the extended arbor of the fourth wheel, and the sweep seconds wheel sits very close to the bridge. This doesn't leave a lot of space between the bridge and the wheel for inserting lifting levers or a wheel puller.

Figure 1. Figure 2.

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I don't use levers, preferring instead to use the Presto-type wheel pullers. I have two models of the Presto wheel puller, the blue-handled one is for wheels with five crossings and the red-handled one is for wheels with six crossings. I don't like the factory finish on these pullers since I think that they can easily scratch the movement during use, so I have modified both of them. The first modification I did was to thin down the notch in the metal puller section that fits under the wheel, to better accommodate narrow gaps found on this movement. Secondly, I polished the bottom surfaces of the pullers to a mirror finish and rounded the sharp edges, to ensure that I leave no trace of the tool’s use on the movement surface. So with my Presto in hand, removal of the sweep seconds wheel is a straightforward task. A word of caution, always make sure that both sides of the tool are engaged properly with the wheel before pulling—if one side disengages during removal you could easily bend the fourth wheel pivot, or damage the sweep seconds wheel.

Next up is the sweep seconds pinion. It's held in place with the sweep seconds tension spring. After removing the tension spring, I always take out the sweep seconds pinion with a piece of Rodico and carefully place the pinion in my parts tray. These pinions have a tendency to reject handling with tweezers during removal and tend to f ly off and disappear, so I don't take any chances. I also never wash the pinion in the ultrasonic machine. If I put the sweep seconds pinion in my normal cleaning basket, the arbor will find its way between the basket mesh and stick out where it could easily be broken. I have cleaning baskets with a finer weave to prevent this, but I find that these baskets have such a fine weave that they don't drain out the cleaning f luids properly. So with all those issues, my method is to clean the sweep seconds pinion manually by soaking it in hairspring cleaner. In the unlikely event that the pinion is gummed up badly, I manually clean it with a sharpened piece of peg-wood, working very carefully to avoid damage. The sweep seconds pinions are normally quite clean and the hairspring cleaner does a good job of removing any oil residue.

The next item I want to mention is the crown wheel screw. As we know, crown wheel screws are normally left-handed; they need to be to prevent them loosening when the watch

is being wound. This is due to the crown wheel turning anti-clockwise during winding, which is the same direction as loosening a normal (right-handed) screw. On this JLC you can see the typical screwhead markings that identify a left-handed thread, those markings are two grooves, one on each side of the screw slot, Figure 3. Whenever you see this type of mark on a screwhead, you know that the screw is left-handed and must be turned clockwise to loosen. Remember the saying ‘Righty-Tighty, Lefty-Loosey’ meaning, of course, turn towards the right (clockwise) to tighten or towards the left (anti-clockwise) to loosen—for a normal right-handed screw. Naturally the opposite applies to our left-handed screw. Unfortunately, this standard three-slot marking is not universally applied to all left-handed screwheads, and you will come across many a left-handed screw with only a central screw slot. Expect to find left-handed screws on the crown wheel and sometimes on the calendar mechanism date finger wheel. For either of these screws I always assume a left-handed thread when I attempt removal. Also note that under the crown wheel you will usually find a thin steel disc, many times this disc will stick to the bottom of the crown wheel and is easily overlooked, Figure 4. This disc prevents wear in that it isolates the brass barrel bridge from the turning motion of the crown wheel, the steel disc providing a harder wearing surface than the brass barrel bridge. With the barrel bridge removed, I found text etched on to the barrel, Figure 5. Since this can only be seen by the watchmaker, you have to wonder why it's there and, more importantly, if the spring does break, are you provided with a free replacement? I doubt it. This is actually a reminder to watchmakers not to install a plain blue spring. At the time when this calibre came out, the use of old-fashioned steel springs was still a habit among the older workers in the industry. A Nivaf lex or similar spring has very different characteristics from a classic blue steel spring, changing the performance of the watch markedly. So a clear reminder like this to independent repairers would have been useful to keep the watch performing well.

As I have mentioned before, higher-end movements have screwheads with fine slots that will normally require you to file or stone your screwdriver blades in order to fit these properly, and this JLC is no exception, Figure 6.

Figure 5. Figure 4. Figure 3.

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After cleaning and inspection, assembly was straightforward. Before you install the seconds hand, you must remember that the tension spring is all that's holding the sweep seconds pinion in place. If during hand installation you don't recognize this fact and press the hand down expecting the tension spring to be able to hold pinion securely, you will be in for a surprise. When installing the hand, it is vital to support the end of the centre seconds pinion directly on a clean stake. The tension spring must be moved aside during this operation, otherwise there is a risk of forming a dimple or peened spot on the spring. Not only is this unsightly, it will introduce unnecessary damage. If you attempt to attach the hand while the spring is in place and unsupported, you risk breaking the spring or the

Figure 9. Figure 10.

Figure 8. Figure 7. Figure 6.

These particular slots were very shallow and thin and I modified the blades to fit accordingly. It was nice to see that the screwheads on this movement were mostly in good condition, with little damage showing from prior botched workmanship. However, the smaller screw that held the lower balance shock jewels spring hadn’t fared so well—it was damaged. The shock jewel settings were a new design I had not encountered before, Figure 7. As I have mentioned before, every watchmaker needs the Bestfit Encyclopedia of Watch Material1 (Parts 1 & 2) and once again, they proved invaluable; I found the shock setting listed as a Parechoc model, factory number 3214–5, Figure 8. If I needed to order parts for the shock settings, then this information would be a must, otherwise how do you describe what you have? In the Bestfit catalogue you will find 33 pages of various shock absorbers; important information that I haven't found anywhere else. The upper shock jewel was of a similar design, but without the screw holding the spring, the spring assembly being riveted to the balance cock and easily moved to one side with the tweezers, allowing removal and oiling of the cap jewel assembly, Figure 9.

pinion, or both. I use my jewelling tool to install the seconds hand. With a f lat stake installed into the tool’s base, on to which I place the movement, making sure that the pinion is centred on the stake, then with a f lat-faced pusher in the upper part of the tool, I carefully press the hand in place, ever so gently as only a little pressure is needed. I don't use the jewelling lever for this operation as it multiplies the force too much; instead I remove the lever and only use my fingers to apply pressure directly to the pusher holder. Normally these seconds-hand pipes are a low-friction fit for that very reason: just a light touch is all that's needed and the hand is properly secured. With the hand secured, a tiny drop of 9010 oil is applied to the tip of the pivot and the spring is moved back into position.

The customer had sourced a new dial and hands and they were installed in place of the old damaged ones. This totally transformed the look of the watch: check out the nice results in Figure 10. A new case-back and crown O-rings were installed and lubricated with silicone grease; hopefully the moisture will stay out of the case this time round, and the dial

will maintain its finish till its next shop visit. A final note: for the naming conventions, I referred to

my Bestfit catalogue since it lists many of these older type of movements and their various parts.

ENDNOTE

1. Bestfit #111 Encylopedia of Watch Material, vol ii (New York: B. Jadow & Sons, 1976) 730.