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Damasko Watch Technology

Watch Case | Gasket System | Magnetic Field Protection | Patented Crown

Bezel Construction
| Stainless Steel | EPS® Spring | Micro Ball Bearing | Rotor | Damest Coating


The Watch Case

Damasko Watch CaseIt has always been one of our major goals to design a watch case with superior resistance against scratches, knocks, and general wear, but the materials commonly available, including the rather soft titanium definitively do not feature the necessary characteristics. The term 316L describes the kind of steel which is predominantly used in the watch industry. It features good corrosion resistance but is also relatively soft. Occasional knocks with a watch made from this material will often lead to serious scratches or dents.

Although there is the possibility to harden the surface of 316L (1.4435) or 1.4301 up to 1200 Vickers by diffusing carbon into the top layers of the steel, there is no way to temper the material. Due to the austenitic structure of the alloy it is impossible to make sure that that steel remains its hardness throughout the body.

Various tests have proved that this kind of surface treatment is not suitable for our purposes because it only hardens the top layer of the metal. This leads to the so-called egg-shell effect. We were able to dent and scratch the “hardened” surface with an ordinary pair of tweezers (which are normally made from spring steel) because the material underneath the hard layer was not able to withstand the pressure.

Due to the reasons described above we searched extensively for better alternatives. In 1994 after five years of research we took out patents for 20 closely related martensitic sorts of stainless steel which highly exceeded our expectations. They are absolutely nickel-free, offer a good corrosion resistance, and can be tempered up to 64 HRC/800Vickers which is four times the hardness of every other steel currently used in the watch industry.

What makes this material so special is the fact that the molten steel is enriched with 0.35% nitrogen under high pressure. Nitrogen and carbon are responsible for the hardness of the alloy. Under normal circumstances it takes about 1% of carbon to temper a martensitic steel up to 60 Rockwell but the low nitrogen content of our steel only requires 0.35% of carbon to achieve this superior hardness and in addition to that leads to an excellent corrosion resistance which is many times higher compared to other temperable martensitic steels. Due to the special process of hardening we call this steel “ice-hardened, nickel-free stainless steel”. This material is patented for our applications and Damasko makes exclusive use of this pioneering material.

The entire watch case, including hardened crown and pushers is designed, engineered, and machined at our factory near Regensburg. Until the end of 2002 we supplied our cases to a well known German watch brand but from now on these cases will only be available through Damasko. After the special heat treatment mentioned above our steel reaches a maximum hardness of 62 Rockwell which makes it superbly scratch-resistant. You have to search hard to find a common household item ( apart from a sapphire nail-file or a brick) that is able to scratch the case.

Due to its superior performances this steel was mainly created for aeronautical use in:

- ball bearings for jet-engines
- rotor bearings for helicopters
- fuel pumps of the “Space Shuttle”
- high-speed bearings in CNC lathes
- dental and surgical instruments

The use of this steel in watch cases is patented for our company.

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The Gasket System

Damasko Gasket SystemThe main operating elements on a chronograph are the crown and the pushers. The crown is used to set the correct time, and in case of a mechanical wristwatch to wind the movement. The pushers are used for starting, stopping, and resetting the chronograph functions of the watch.

These operating elements basically consist of the visible piece of the crown and chronograph button and a shaft which connects them to the movement.

One of the major problems we had to face during the construction of our new crown and pusher system was to find a solution to seal the operating elements against the ingress of moisture and dust. Conventional systems make use of two O-ring gaskets made from an elastic material such as Nitril™. The longevity of these gaskets is to a large extend determined by the quality of the material and the friction between the stem and the O-ring. This friction factor increases the wear and ultimately leads to worn out and leaking sealing elements.

After extensive research we found a solution to the problem – our lubrication cell. Once again the concept for this unique element is a miniaturized design derived from industrial engineering. The lubrication cell is basically a tube made of our patented hardened stainless steel which is screwed into the drill holes for the crown and the pushers. The cell is filled with a synthetic viscous lubricant and sealed with two innovative Viton™ elements which prevent the filling from leaking or migrating.

The lubricant fills the microscopic surface roughness of the polished crown and pusher stem and eliminates friction and wear. Our lubricant system offers a longevity of gaskets and operating elements which is second to none.

Our gasket system and lubrication cell are patented.

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The Magnetic Field Protection - The Case inside the Case

Damasko Magnetic Field ProtectionEvery Damasko watch features an important technical detail which is not visible at first sight but has a major influence on its accuracy under harsh conditions – the anti-magnetic cage.

Only very few mechanical pilot’s watches are equipped with this feature. The unique inner case consists of the dial, the movement retaining ring, and a second back. These parts are made of a special material with anti-magnetic characteristics which is able to withstand magnetic fields with a strength up to 80,000 A/m. They are machined with maximum precision to ensure an exact fit and to prevent the escapement from being magnetically charged.

The magnetic field protection in combination with martensitic ice-hardened steel is patented.

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The Patented Crown

Damasko Patented CrownDuring the development of our new crown we had to face the fact that literally every current crown system that works on a basis of a decoupling screw-down crown has two major weak spots that may sooner or later result in a defect.

The reason for that is to be found in the positive-fit coupling elements of the crown. They often consist of a fairly weak hexagon bolt which with1mm width across flats. Another reason for a defective crown mechanism is the wrong choice of material. Most watch manufacturers still make use of brass, German silver, or rather soft stainless steel (see “The Watch Case”). this leads in many cases to chamfered corners of the hex bolt which makes a form fit almost impossible. In such a case you would neither be able to wind the movement by hand nor to set the correct time.

Many watch manufacturers seem to be aware of this problem and use an inferior coupling crown which is permanently connected to the movement. The wrong choice of materials described above also sometimes results in ruined and worn out threads of the crown mechanism which also impacts the water resistance of the watch.

After extensive research we developed a decoupling screw-down crown which is constructed according to standards derived from mechanical engineering. The use of a hex bolt with 2mm width across flats and the fact that the entire crown, including shaft, thread etc. is made from our patented hardened steel (60-62 HRC) results in a longevity which is second to none.

All gaskets of the new crown system are made of Viton™, a material with high chemical and mechanical resistance which is superior to every other gasket material (Nitril etc.) currently used in wrist watches.
Crown and pushers are also equipped with our patented lubrication cell which ensures a smooth action and lubricates the shaft and the gasket. The tubes of both crown and pushers are, according to industrial engineering, screwed into the case using a special key. Almost every other watch manufacturer makes use of an inferior press fit tube.

Our new crown system is patented.

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The Bezel Construction

In the following images we would like to give you a rare insight into our currently used bezel constructions (patent pending). We would like to illustrate how we achieve an ultra precise and reliable bezel action. CAD/CNC designed and engineered, hardened components guarantee that our bezels ratchets will never wear out, or become loose. Get a view on bezel parts that even Damasko owners will only hardly ever see.

Damasko Bezel
Damasko Bezel
Damasko Bezel
 
Click images to enlarge
 
Damasko Bezel
Damasko Bezel
Damasko Bezel

No other bezel available offers that amount of precision and performance even under harshest conditions.

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The Stainless Steel

Due to the fact that we are well known experts on stainless steels and their metallurgical aspects, we are often approached by watch enthusiasts and customers from all over the world. And more or less all of them ask the same questions: Which steel used for watch cases offers the highest corrosion resistance, and which one features the greatest hardness? Which company offers the best choice?

Although it is possible to answer this question in one sentence, we feel that it might be of greater interest to compare the most commonly used stainless steels with each other, including one of our steels.

For our upcoming automatic pilot’s watch range (DA 36/46) we’ve chosen a highly corrosion resistant austenitic stainless steel alloy which can be fully hardened, leaving the surface with a key hardness of 1600 HV (Hardness Vickers). Just to give you an impression how hard this actually is: Titanium 180-210 HV, St. Steel AISI 316L 190-220 HV, Sapphire crystal 2000 HV.

In order to compare our new steel with other commonly used stainless steels, we’ve decided to measure the PRE-factor (Pitting Resistance Equivalent). This can be done by defining the ratio of three important alloy components, using the following formula:

PRE = %Cr (Chromium) + 3.3 x %Mo (Molybdenum) + 30 x %N (Nitrogen)

This leads to the following results:

1. Stainless steel AISI 304 (watch cases, not in common use): PRE-factor 20
2. Stainless steel AISI 316L (commonly used for quality watches): PRE-factor 26-30
3. Stainless steel AISI 904L (marine hardware, etc.): PRE-factor 35
4. Stainless steel used for latest strategic developments of the German Navy, e.g. 1.3964/1.4566: PRE-factor 38
5. Stainless steel DIN 1.4456 (high grade alloy used for medical implants): PRE-factor 52
6. New Damasko stainless steel used for the upcoming DA 36/46: PRE-factor 50-52

We think that this table perfectly illustrates the superior corrosion resistance of our new steel. Soon we will also discuss how we achieve the tremendous hardness of this pioneering material.

By the way: Since most quality watches are made from 316L they don’t offer real salt water resistance, so always make sure to rinse your sports/dive watch with fresh water after open water swimming or diving.

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The EPS® Spring

Isochronism is the essential element of any chronometry based on oscillations of whatever kind: the oscillations of a pendulum, a quartz crystal or a balance. The more regular the oscillation occurs, the more regular is the movement rate and the better can it be adjusted for best possible accuracy. If a control mechanism oscillates fully regularly, it is called isochronous (Greek for “occurring at equal intervals”). In this context, isochronism of the classical balance on transportable mechanical watches has proven to be the greatest challenge for watchmakers and engineers. Major interference factors include primarily

* the asymmetric development (transient and dying out oscillation, resp. breath) of the spring,

* the change in the elasticity of the spring depending on the temperature,

* the influence of magnetic noise fields,

* mechanical and thermal changes to the material at both fixation points of the spring,

* the influence of the centrifugal and gravitational force on the spring,

* the unbalance of the balance wheel,

* the play between the regulator pins.

The properties of the EPS® material alone do not suffice to solve the phenomenon of asymmetric development of a flat spiral spring. For this reason, our team of researchers looked for a method and found one in a new type of end curve design, which could be realised within the oscillatory level of the spring. This is shown in an obvious thickening at the outer end, which forces the EPS® spring into a concentric development, as a result of which the transient and dying out oscillation occurs symmetrically to the centre of the spring on all sides of the oscillatory level. This ideal form of thickening was registered as a patent.

The EPS® spring is manufactured in one piece, which means that is has an integrated collet for fixation to the balance staff, and at the outer end it is “clipped” into the stud in a very precisely defined area. The minute clamping jaws of this stud are designed resilient, so that the clip-on point of the spring can still be corrected by pulling or pushing the spring through the stud. This new type of stud design was registered as a patent.

On conventional springs, the inner end is affixed to the collet by soldering, welding or clamping. This causes a structural modification of the spring material at the fixation points due to squeezing or heating, which on the other hand requires additional adjustment works.

With our EPS® spring, we have created an oscillating mechanism that provides multiple decisive advantages: the EPS® spring oscillates ideally concentric. It is designed for isochronism independently of the temperature, of the position of the movement and of magnetic fields.

EPS® springs with uniformly identical quality:

As in the case of the silicon escape wheel, the EPS® spring is produced in a DRIE (deep reactive ion etching) process, which is described in more detail at a later stage. The material has a uniformly fault-free polycrystalline structure and can be machined with tolerances in the micrometer range. Accordingly, all EPS® springs are of uniformly consistent and extremely high quality, which is transferred onto to the accuracy of the movements fitted with these.

The EPS® spring is the result of the consistent innovative policy of our manufacture. With this development, Damasko is amongst the leaders in innovation and at the same time sets decisive accents in order to furnish its novelties with an exclusiveness that is typical to the brand using significant distinguishing features. Also in the case of the EPS® spring, it is the objective of this innovative philosophy to increase the accuracy and stability of mechanical watches, as well as raise the durability and sustainable value of Damasko watches.

Damasko will still carry out numerous tests before this new EPS® spring can be integrated in wider serial production.

EPS® spring by Damasko at a glance

* Produced by deep reactive ion etching (DRIE) method and registered as a patent

* Concentric development that improves isochronism on the basis of a geometry that is registered as a patent

* Anti-magnetic

* Temperature compensation due to material properties

* Contrary to conventional springs, no thermal or mechanical impairment at fixation points

* Insensitivity to minor shocks

* Reduced sensitivity to centrifugal and gravitational forces, as the EPS® is three times lighter than conventional springs

* No impairment of movement rate due to recurrent minor shocks in daily use

* Complies with NIHS standards for coincidental standardised shocks

The following images illustrate the flexibility of our EPS® springs:

Image 1 shows the spring in a non-tensioned condition – absolutely plane at flat level
Image 2 shows the spring out of the flat level drawn approx. 6-7 cm – the individual turns are subject to strong torsional forces
Image 3 shows the spring again after the tension test in a non-tensioned condition. It is absolutely plane again at flat level - without any permanent plastic deformation


Image 1


Image 2


Image 3

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The Micro Ball Bearing

From the beginning, ease of servicing and durability were in the foreground for the design of our new calibre A35. For this reason, we decided at a very early stage already to place the complete winding mechanism on lubricant-free four-point micro ball bearings. The result of this is that frictional losses are reduced to a minimum.

Also for the design of our rotor fabrication for various calibres, it was our objective to make the rotor bearing lubricant-free, quiet and shock-proof, but also to keep the tilt angle as small as possible.

However, as the tilt on a normal micro ball bearing is too large due to the geometry of its raceway, these were unsuitable for our purposes.

The so-called 4-point micro ball bearings already in use in the watch industry, which have a divided inner race and where the bearing clearance is adjusted by connecting or pressing on the 2nd taper ring, were also taken into account.

However, the attempts to adjust the radial play or tilt in a defined way turned out to be difficult due to pressing of the taper ring on a divided four-point bearing on the inner race at an outer diameter of <2.7mm.

A bearing with a precisely defined play had to be developed, as our crown wheels only run on a one-sided bearing in the inner race of the bearing and “tilting away” under stress had to be limited to a negligible minimum. We found the solution in a new raceway geometry for our micro ball bearings. Based on this geometry, the necessary 4-point contact was also achieved. The advantage is that the bearing consists of a single-piece inner and outer ring. In production, these can be machined with closest work tolerances, and afterwards the bearings are assembled using ceramic balls with a precisely defined size or dimension. This way, for example, radial plays of 5.10 or 15µm can be adjusted without any problems.

In addition, the resulting very small realisable radial play only permits a so-called tilt in the µ range, which is of major importance for rotor bearings.

Also to be mentioned is that our new bearings are manufactured from non-corroding special steel and are fully hardened, as it is quite common in the watch industry that the pressed-on taper ring on the inner race on multipart four-point bearings is made of toxic copper beryllium bronze.

As the ceramic balls can be manufactured with a superfine surface structure and neither microbonding nor frictional corrosion occurs, a lubricant can be omitted completely. And since no lubricants can age in this way, an unlimited lifetime is the result.

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The Rotor

In the course of the development of our self-manufactured calibre A35, for which also a new winding concept was worked out, the familiar “double eccentric winding system” was created.
In order to be able to produce this in an optimal way, both from a technical point of view as well as in terms of quality, we decided to produce all important key components ourselves.
In addition to the bearing of the winding device (see section “Micro ball bearing"), the focus of attention now moved onto fabrication of the winding mass, the so-called rotor.

Today, after establishing the production and assembly process, we are in the position to manufacture all the rotors used by us ourselves. In addition to that, this fabrication was expanded further due to increased enquiries by other watchmakers, so that we are able to manufacture rotors for all current automatic calibres. At this point, we benefit from the fact that these can be equipped either with a standard ball bearing or with our own micro ball bearing.

Special models or even new developments can be realised within a short time, whether of one piece or multipart, e.g. with hard metal segment. Moreover, surface refinements such as perlage, Geneva Stripes or the like can be realised. Besides, any imaginable milling or laser engraving is possible.
Even such surface refinements as gold-plating, rhodanizing or PVD-coating do not represent a problem.

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The Damest Coating

In everyday life wristwatches are subject to hard use, which unfortunately can make marks on the case. Damasko has set the goal of manufacturing watches which brave the perils of everyday life and serve as a time keeping instrument for years without acquiring marks to show the age of the watch or reveal the hard life of the owner. The Damest coating is another innovation to support this goal.

The Damest coating protects the watch with its special structure, like no other coating, to maintain a new appearance. The special coating of Damest is a proprietary multi-layer composition. The foundation is the case material of martensitic stainless steel with a hardness of about 740 HV. This ensures a stable and impact-resistant base layer, which supports the upper layers and prevents them from breaking under stress. An intermediate zone about 1.5 µm (microns) thick is created by ion implantation on the surface of the case. This region is strong with hardness about 1500HV. It acts as a bonding layer between the case and the multi-layer coating.

The coating layer adheres to this region and spalling is prevented. The Damest multi-layer coating is applied in a PECVD process. The combination of layers is about 7µm (microns) thick with an outer hardness about 2500HV to resist abrasion. Some of the intermediate layers of the coating have a certain elasticity. By keeping the layers thin, the outer layers can deflect enough to resist chipping from impact without enough deflection to crack. The result of this combination of layers is a hard coating with high resistance to scratching the surface. So, the watch can look new for years.

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