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Ichihiro
The "Spiralists"
Hairspring production at A. Lange & Söhne
It weights slightly more than two milligrams. It is smaller than a thumbtack head and thinner than a human hair. And it is the pulsating heart of every wristwatch: the balance spring, or hairspring as it is also called. Perhaps only half a dozen watch companies in the whole world make them in-house. And A. Lange & Söhne is one of these chosen few. Since 2003, the vener able Saxon manufactory has endowed a growing number of movements with its pro prietary balance springs. Meanwhile, they oscillate in one out of two Lange movements.
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Tiny. Vital. The balance spring. | Since the DOUBLE SPLIT, a spectacular double-rattrapante chronograph, was launched seven years ago, Lange has steadily increased the number of manufacture cali bres with its proprietary hairsprings. At this year's SIHH alone, the Saxons presen ted five new models with springs developed and manufactured in-house. So now, half of the 24 current Lange calibres are equipped with them (see table on page 2). |
 Exclusive trio with the Lange hairspring: the "165 Years – Homage to F. A. Lange" anniversary edition | Lange's balance spring manufacturing ca pability is based on an ingenious and elabo rate system that Günter Blümlein began to develop in the 1990s. After all, hairsprings are part of the Lange heritage: the metal alloy still ubiquitously used today dates back to 1930 and to Richard Lange, Ferdinand A. Lange's eldest son. The scien tist in the fam ily was the first to discover that the admix ture of beryllium in steel-nickel alloys deci sively improved their elasticity and thermal resistance. |
| Year | Model | Calibre |
| 2004 | DOUBLE SPLIT | L001.1 |
| 2005 | TOURBOGRAPH "Pour le Mérite" | L903.0 |
| 2006 | RICHARD LANGE | L041.2 |
| DATOGRAPH PERPETUAL | L952.1 | |
| 2008 | CABARET TOURBILLON | L042.1 |
| 2009 | RICHARD LANGE "Pour le Mérite" | L044.1 |
| LANGE ZEITWERK | L043.1 | |
| 2010 | LANGE 1 TOURBILLON "Homage to F. A. Lange" | L961.2 |
| 1815 MOONPHASE "Homage to F. A. Lange" | L943.2 | |
| RICHARD LANGE "Referenzuhr" | L033.1 | |
| LANGE 1 DAYMATIC | L021.1 | |
| 1815 CHRONOGRAPH | L951.5 | |
| Meanwhile, Lange has equipped 12 calibres with its proprie tary hairsprings | ||
Even today, the development and pro duction of reliable balance springs is associated with nearly insurmountable technical obstacles. The slightest devia tions from specified manufacturing tol erances or sequences in the multi-stage production process would have serious consequences with respect to the rate accuracy of the watch. This is why most watchmaking companies don't even con sider getting involved in such an intricate undertaking.
The first difficulties are already en coun tered at the first stage during which the wire, made of a steel-nickel alloy, is drawn. Several times in succession, it is pulled through progressively smaller diamond dies until it has attained its final diameter of down to 0.05 millime tres. Then, between two extremely hard metal cylinders, it is rolled to a strip with a cross section measuring 0.018 by 0.09 millimetres. Uncompromising precision is ab solutely crucial. This is because in the assembled watch, a deviation of just one ten-thousandth of a milli metre can cause a rate diffe rence of about three minutes. The spe cial rollers used by Lange are ground in the in-house toolmaking depart ment. No outside supplier would be capable of delivering rolls to the required toler ances.
The next step involves measuring the strip after it has been rolled. A laser inside the roll mill measures the width, but it still lacks the precision to dependably meas ure the thickness of the strip. For this purpose, a defined section of strip has to be weighed. Then, using a special formula, the thickness can be determined with sufficient accuracy.
The rolled strip is now precisely cut into pieces of identi cal length. Three, four, or five of these pieces are pedantically coiled around each other by hand. This is how the hairsprings are ultimately formed. Up to 40 of these coiled packs are stacked in a metal ring. In a vacuum furnace, they are subject to a sta bilising heat treatment at a temperature of several hundred degrees Celsius. The permissible tem pera ture deviation during this phase is less than one de gree. After the hairsprings are separated, collets are laser-welded to their inner ends. Finally, the hair springs are cut to the desired number of wind ings. Now, they are ready to be connected to the balance.
But first, they have to be classified to assure that the balance spring and the balance truly constitute a harmonious pair. This is done with a method that accurately measures the moment of elasticity of the hairspring and assigns it to one of 20 classes. Then, the hairspring can be paired with a balance that has precisely the right moment of inertia. This eliminates pairings that would cause exces sive rate deviations.
The process of bending the terminal curve calls for extreme sensitivity. It is decisive for the regularity of the hairspring's oscillation behaviour. This applies in par ti cular to the so-called "Breguet overcoil" for which the outer end of the spring is bent upwards and then folded inward on a sec ond plane above the spring. For this critical procedure, which allows only one try, an experienced watch maker spends about two to three hours. But if he succeeds, the bal ance spring will "breathe" about 200 million times a year with impeccable uniformity.
 |  |  and balance wheel with eccentric poising weights. |
Lange's technological know-how and in-depth experience in the domain of oscillation systems is in no way limited to the production of balance springs, by the way. Special springs like those that re-tension the constant-force escapements of the LANGE 31 and the LANGE ZEITWERK are also crafted in-house. And the balance wheels with eccentric poising weights, perfectly matched in their characteristics to Lange hair springs, are produced on-site as well. Meanwhile, this lightweight and precisely adjustable system has been deployed in seven calibres. Thanks to the interaction of these two compo nents, Lange watches are adjustable to a rate accuracy that is second to none. This achievement reflects a horological understanding with an ultimate goal that can be expressed in one word: precision.
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