Double-Checked is Better – Two-Fold Assembly

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Double-checked is better – two-fold assembly
Journal 2020
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The motion is hardly discernible with the naked eye. With great caution, the watchmaker uses narrow tweezers to grasp a golden wheel by its outer edge and wiggles it just a little bit. The loupe in front of her right eye is merely a few centimetres away from the movement. In this situation, a deep breath would be fatal. Then, she raises her head and swaps the tweezers with a thin screwdriver to loosen the individual screws of the train bridge, a routine step. She carefully lifts the bridge out of the movement and places it on a small green apparatus. It allows her to press the bearing of the wheel deeper into the gold chaton by one hundredth of a millimetre. “To assure precise functionality, the arbor of the wheel should neither jam nor have too much play,” says Tino Bobe, director of the A. Lange & Söhne manufactory, as he explains this step in the initial assembly of the LANGE 1 MOON PHASE. “To give it the correct endshake, the position of the bearing jewel is shifted by a minuscule amount.”

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Again and again, the three-quarter plate is screwed on and off until all endshakes are optimally adjusted and perfect interaction within the wheel train is achieved. In the process, the young woman wears white finger cots that are hardly visible at first sight.
438 parts – assembled by hand
“They are indispensable,” notes the 51-year-old Dresden native who has been supervising the manufactory since 2004. “All frame parts of our watches are made of untreated German silver. It is an extremely sensitive alloy.” Every fingerprint would leave lasting traces and prevent the formation of the beautiful patina with which the metal protects itself against corrosion.
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Each A. Lange & Söhne watch is assembled twice and German silver is one of the reasons for this effort. Despite all the precautions, the work involved in the numerous adjustments during initial assembly heightens the risk of damaging the material. So once the watch has been completely assembled and checked for accuracy with the timing apparatus, the watchmaker takes all 438 components apart again and places them in various small containers. “At this point, they are cleaned,” Tino Bobe explains. In a finishing department, the three-quarter plate is decorated with Glashütte ribbing, which gives the watchmaker the time needed to mirror-polish the gold chatons.
Every work step twice – for the sake of beauty
But why this effort? “Simply put, German silver is truly beautiful. In time, it takes on a fine golden hue and impressively emphasises the Glashütte ribbing on the three-quarter plate,” Tino Bobe adds. Beyond that, it is a particularly robust material that allows thin silhouettes, mainly where complications are involved. That is why Ferdinand Adolph Lange was already using this German silver for the frame parts of his pocket watches.
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Later, when all 438 parts are returned to the watchmaker’s bench, the calibre L121.3 is assembled a second time. Brand new blued steel screws replace the previously used temporary ones because they, too, just like the entire movement, must be scratch-free. “After all, our movements are visible through the sapphire-crystal casebacks, so we want them to be immaculate,” says Tino Bobe. In the end, the finished movement of a LANGE 1 MOON PHASE will materialise on this table. Only when it has also passed the second test on the timing apparatus will it be fitted with a dial and hands in another department and then cased in pink gold.

There are two sides to immaculacy. Obviously, it is forever unattainable. Then again, some people spare no effort to gradually approach it step by little step. That, in a nutshell, is the Lange way. The watchmakers in Saxony have but one goal: the perfect timepiece. All processes and procedures are aligned with the ambition to again push the limits of feasibility just a bit beyond where they seem to be. One of the consequences is that at A. Lange & Söhne, every movement is assembled twice. It makes no difference whether it is a simple three-hand calibre or a complication. And there are convincing reasons to do that.

One of them is related to a special design feature – the three-quarter plate introduced by Ferdinand A. Lange in 1864. On the one hand, it enhances precision by stabilising the entire wheel train beneath a single bridge. On the other, it makes assembly more difficult because even an experienced watchmaker has to mount and remove it several times in succession until each individual arbor has just the right endshake.

The other reason relates to the material of which the plate is made. At Lange, all plates and bridges are made of German silver. It is responsible for the rigidity of the movement and in the course of time develops a warm, golden patina that protects its surface. That is why the material is left „untreated“. Unfortunately, it has a disadvantage: a very sensitive surface. Every fingerprint can leave a lasting blemish and tools like screwdrivers may cause scratches.

This is why at A. Lange & Söhne many hours are invested in assembling each movement with utmost virtuosity. Afterwards, the interactions of all mechanical parts are adjusted to the highest degree of perfection. But then, the movement is taken apart again. Now, all parts are painstakingly cleaned, and many of them are lavishly decorated and polished. Even parts that later remain unseen are enhanced in this way. The jig screws used to assemble the raw movement are now replaced with new, thermally blued screws. When the three-quarter plate has been decorated with the characteristic Glashütte ribbing and the last gold chaton has been mirror polished, the movement is reassembled for the second and last time and carefully lubricated at over 50 oil sinks and bearing points with up to eight different greases and oils.

Twofold assembly as performed on the RICHARD LANGE TOURBILLON „Pour le Mérite“

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The assembly of a Lange calibre takes place in a long succession of meaningfully organised steps: First, the parts that have been lavishly finished by hand are clustered in so-called subassemblies that in turn are then merged to complete the entire movement. Here, the chain – it alone consists of more than 600 parts – is carefully wound around the spring barrel.

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A small group of specially trained watchmakers devotes its undivided attention to a very special subassembly that requires a keen eye and the ultimate in dexterity: the tourbillon. It consists of 84 individual parts that together weigh no more than one-fourth of a gramme.

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The assembly of the planetary gearing also requires extremely rare skills. After all, 38 tiny parts have to be accommodated in the fusée which has a diameter of only ten millimetres.

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A special tool is used to fit the chain into the fusée’s grooves. Then, the finished movement is handed over to the reglage specialists who, as the engraving in the plate indicates, precisely adjust it in five positions.

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The wheel train that indicates the time is now mounted on the dial side. The adjustment of the individual endshake tolerances requires considerable dexterity.

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The pivoting dial segment mechanism is positioned and secured with screws. This procedure may need to be repeated several times to make sure all arbors have the right endshake. The mechanism assures that the subsidiary dial element is advanced by 90 degrees every six hours. Thus, it fully exposes the tourbillon from 12 to 6 o’clock and assures that the hour dial delivers a precise reading of the time from 6 to 12 o’clock.

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Once the tourbillon cage has been integrated and attached to its bridge, the pivoting dial segment can be added. This completes the first assembly pass.

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Now, the perfectly adjusted movement would be ready for integration in its case.

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Instead, the movement is entirely taken apart again. The components are thoroughly cleaned in an ultrasonic bath. To assure the absolutely flawless presentation of the movement through the sapphire-crystal caseback, some parts are only now painstakingly decorated. The second assembly pass can begin.

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In the second, final assembly phase, one single watchmaker is responsible for the entire movement. The three-quarter plate made of German silver was embellished with traditional Glashütte ribbing. All gold chatons have been manually polished and carefully inserted in the plate. The jig screws previously used were replaced with gleaming thermally blued screws.

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The last step involves the placement of the pretensioning ratchet. The movement is finished and can now be cased up. Then, the watch must demonstrate its functional integrity and precision in an accurately defined procedure that can last several weeks.

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After the strict final inspection, the RICHARD LANGE TOURBILLON “Pour le Mérite” is ready for delivery. Somewhere in the world, a watch enthusiast is impatiently waiting for its arrival.
 
:up:A very interesting read!:wink: Thanks for posting this up, Mike.:hat:
 
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