Blade steels: For the “heart” of the knife, the blade, ROCKSTEAD uses two of the best blade steels currently available: the powder-metallurgy steel ZDP-189, specially developed for knife blades by Hitachi, and the “high-speed steel” YXR-7, known for its particular toughness. Decades of experience in the production of cutting tools have enabled ROCKSTEAD to develop manufacturing processes that guarantee the best properties for knife blades with these steels.
The premium blade steel ZDP-189 is produced through powder metallurgy and was specially developed by Hitachi Metals for cutting tools, particularly knife blades. It has a particularly fine and even micro-structure and stands out for its extraordinary resistance to wear and tear and its outstanding corrosion-resisting properties. In order to bring together the best properties of this material in the form of a knife blade, a very precise heat treatment is required. In its processing of this steel, ROCKSTEAD achieves hardness of up to 67 HRc. However, the ZDP-189 only reveals its full cutting performance with the application of suitable blade geometries (HONZUKURI and SHINOGIZUKURI), as used by ROCKSTEAD. Knives with blades made from ZDP-189 retain their sharpness for longer. As ZDP-189 is not quite as tough as YXR-7 (see below), these blades are not recommended for “striking” cuts. Composition: the precise composition is not known. At this point, therefore, only the most important elements can be outlined: carbon: 3%, chrome: 20%, molybdenum: 1.30%, tungsten: 1.50%, vanadium: 0.10%.
(Laminated steel) Above all in order to give greater stability to larger blades made of the ZDP-189 blade steel, some of the premium ROCKSTEAD models are manufactured using a “composite blade” (laminated steel). Currently VG-10 stainless steel is used for the external layers – a material favoured by many knife manufacturers thanks to its good resistance to wear (possible hardness up to 62 HRc) and to corrosion. In earlier models, ATS-34 steel was used in place of the VG-10 steel. If you observe a blade like this very precisely, you will be able to see a fine line above the cutting edge that looks like the “hamon” (the hardness line of Japanese blades). In our ROCKSTEAD shop these blades are labelled with “ZDP-189 clad by VG-10” or “ZDP-189 clad by ATS-34”.
The blade steel YXR-7 is a high-speed steel (HSS) that is likewise manufactured by Hitachi Metals. The steels in the YXR series are high-strength and particularly tough. They are used primarily as stamps and templates for hot, semi-hot and cold working and also as deburring templates. They have already won numerous awards for their effectiveness as shaping and tool steels. In spite of its tremendous hardness (around 65 HRc), the YXR-7 steel boasts outstanding toughness thanks to its low carbide segregation. In comparison to the ZDP-189 blade steel, however, its corrosion-resistance is poor, so ROCKSTEAD chooses to coat this blade steel. The coating is applied to the entire surface of the blade, and is then removed from the cutting edge alone. It is therefore recommended that knives be wiped dry after use in order to prevent rusting. Knives made with this blade steel are extremely robust and particularly suitable for heavy work and “striking” cuts. Composition: the precise composition is not known. At this point, therefore, only the most important elements can be outlined: carbon: 0.8%, chrome: 5%, molybdenum: 5%, tungsten: 1.10%, vanadium: 1.10%.
The coatings of the YXR-7 steel:
Since the YXR-7 blade steel is less resistant to rust than the ZDP-189 blade steel, the blades of all ROCKSTEAD knives that are made out of this steel are coated. ROCKSTEAD most often uses the DLC (Diamond Like Carbon) coating, which boasts hardness of up to HV1800. For some years now, blades have also been given a titanium coating (TIN or HPC). This is even harder and therefore more resistant to wear and tear than DLC. It reaches hardness of up to HV3000 and boasts an even lower friction coefficient. It is possible to tell these two coatings apart by their colour. DLC is very dark, almost black. Titanium coatings, on the other hand, tend to be lighter and have a bluish or violet sheen.
Other material: ROCKSTEAD knives are perfected through the use of the best materials ideally suited to their purpose. These include: hardened aluminium, titanium and waterproof desert ironwood for handles and grip plates, and selected parts of the skin of stingrays for inserts or handle covers. The processing of all components takes place within the lowest tolerances and at the highest level of quality.
ROCKSTEAD uses two aluminium alloys. Duraluminium, also known as A2024, is an aluminium alloy that stands out particularly in comparison to pure aluminium thanks to the high strength and hardness achieved, as well as its particularly high resistance to corrosion. The alloy A6063 also boasts greater hardness and strength than pure aluminium, as well as a very high quality of surface. The ROCKSTEAD models HIGO, HIZEN, TEI, SHIN, KOU and CHI have handles made of these materials.
Titanium is much lighter than steel, but also boasts remarkably high strength and is corrosion-resistant. Although it is not easy to process, these properties mean it can be used in a variety of different ways. At ROCKSTEAD, the Gentleman Knife SHU is currently manufactured with titanium grip plates.
ROCKSTEAD uses this wood for handles, for example with the models HIGO-X or CHOU-IW. One of the first sheath knives produced, the JIN model boasts a handle made of this unusual material. Ironwood is heavy, very dense and is one of the most resilient of all woods. The remarkable patterns and strong contrasts in its colouring also make it an unusual yet pleasing material.
Micarta is a so-called fibre-plastic composite. During its manufacturing process, various plates or layers of an absorbent carrier material, such as wood, linen or cellulose, are soaked in phenolic resin and then pressed into a whole under high pressure. After the synthetic resin has hardened, Micarta is very easy to work and/or grind, and in the process a grain appears where differently coloured materials are used. Micarta is pleasing to the touch, very natural-looking, and is waterproof. Another advantage is that it can be stained almost any colour. It is thus unsurprising that Micarta is one of the most frequently used handle materials. ROCKSTEAD uses this practical, long-lasting and visually appealing material in the models KON-ZDP (brown) and KON-DLC (black).
Inserts stingray leather are rare and can generally only be cut using special tools. The hardness of the pearls makes them reminiscent of glass pearls. In Japan, stingray is traditionally used for inserts or as a cover for handles. It prevents slippage and is extremely resilient. ROCKSTEAD uses only selected parts that must visually suit each knife. For processing, ROCKSTEAD has developed special procedures that make it possible to produce extremely precise, perfectly tailored inserts. This ensures that the inserts continue to fulfil their function even after many years of use. Stingray is currently used in the folder models TEI, SHIN, KOU and CHI, as well as for the handles of GI and UN. Here, the handle of a GI or a UN corresponds entirely to that of a katana, both with regard to the use of Stingray leather and as regards the execution of the handle cover. These handles are manufactured specially for these knives using traditional methods in a specialist workshop.
Specific features: Alongside the heat treatment optimised for these steels, it is the blade geometries (HONZUKURI and SHINOGIZUKURI) and the mirror polish applied across the entire blade surface that form the basis for the unique properties of a ROCKSTEAD knife.HONZUKURI:
This dual-sided, convex-curving blade surface – HONZUKURI – is based on the blade forms of the Japanese katana. It guarantees maximum cutting performance and lasting edge-holding ability. These blades are also aesthetically exquisite, and their production is particularly time-consuming and costly.
With the second blade form used by ROCKSTEAD – SHINOGIZUKURI – the surface is not convex, but shaped in surfaces with angles of 30 and 24 degrees. These degree values are the result of intensive investigations by ROCKSTEAD regarding the optimum transfer of force. This form also promises outstanding cutting performance and lasting sharpness.
The immaculate mirror polish typical of all ROCKSTEAD blades is far more than just a smart finish. It reduces the development of nicks and improves the knife’s cutting performance significantly. Even if this perfect mirror finish has a practical purpose, it is also the expression of a unique aesthetic, which ultimately reflects ROCKSTEAD’S perfectionism in the production of each individual knife. This mirror polish is a particular mark of quality and can only be found with this level of perfection at ROCKSTEAD.Cutting performance:
The quality of a knife is defined first and foremost by its cutting performance. Optimisation of this was and remains the primary goal ROCKSTEAD pursues in the development and production of knives.
Care and maintenance:
Your ROCKSTEAD needs regular care and maintenance too. This is particularly easy with the HIGO model, which is supplied with a matching torx tool for dismantling the folding knife. The structure is simple enough so that the knife can be cleaned quickly and easily even when very dirty. A drop of oil (for example WD-40) from time to time will do all ROCKSTEAD knives good. Knives with blades made of YXR-7 should basically be wiped dry after each use in order to prevent possible corrosion. The most important measure, however, is polishing the blade after more intensive use. This way, the tiny bits of damage on the cutting edge that inevitably occur during use can be removed before they develop into larger nicks. The method that is the most suitable in our experience and yet is still very easy is described by ROCKSTEAD on their website under the keyword “Maintenance”. If sharpening is subsequently required as time goes on, you can take advantage of ROCKSTEAD’s lifetime complimentary sharpening service. You need only pay the cost of sending the knife to Japan and for its return.
Repairs: In case of greater damage to the blade or other defects, ROCKSTEAD will generate a quote for you and will only carry out a repair on your express instructions. Otherwise your knife will come back to you “merely” sharpened. With the correct handling and maintenance in accordance with instructions, you will be able to maintain the outstanding sharpness of your ROCKSTEAD knife for many years, without having to have it re-sharpened.
For all questions concerning the details of the manufacture of a ROCKSTEAD knife and in relation to the materials used as well as care and maintenance, or to take advantage of the guarantee services, we would be happy to help you. Write to us or give us a call! If you wish to take a look at the ROCKSTEAD knives in our collection or try them out, we would be delighted to arrange an appointment for you at our site.
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