The finer and more closed the cutting edge in the front micro-area, the better the edge retention. And the finer and sharper the blade, the better the knife's cutting act on the product being cut. As a result, less pressure can be applied and the cutting edge becomes less damaged. The knife remains usable for longer.
Tip: Sharpening the knife on a regular basis with a very fine sharpening steel or stone increases the knife's cutting capacity.
Tip: Make sure when buying the knife that the cutting edge has no burr or roughness (very fine nicks) whatsoever.
The more resistance a blade is to mechanical wear the better its edge retention.
Camber grinding and cutting angle
Professional chef and butcher knifes are exposed to diverse conditions. No two cuts are alike. High mechanical compressive load and different product types damage the cutting edge.
For optimal blade retention to be achieved nonetheless, a relatively blunt cutting angle is recommended. GIESSER knives are sharpened innately with an angle of von 40°! (20° on both sides).
Tip: The blade should be guided at an angle of 20° even when using sharpening steel.
The selection and execution of the hardening process for the knife blades is of overriding importance to cutting performance and rust resistance.
GIESSER relies here on the modern technology of hardening in a vacuum. To the exclusion of air, the blades are heated up to approx. 1050°C over various heat stages and then cooled down with liquid nitrogen. This results in an extremely fine structure of all steel components. Any possible caking is avoided.
The change to the microstructure, however, also causes stresses during the hardening process. And so a second process, that of "tempering", follows. The blades are heated up to approx. 200°C and then cooled with air.
The result is a blade with optimal toughness and a Rockwell Hardness (HRC) of 56–57.
Hardness as a concept
Where HRC values are below 54, the blade is relatively soft. It soon blunts. But the blade is easier to re-sharpen. HRC values of over 57 mean a high degree of hardness and relatively high edge retention. The disadvantage, however, is that as a blade's hardness increases, it becomes more difficult to re-sharpen.
An HRC of 55–57 is the ideal balance between edge retention, material usage and re-sharpening behaviour.
Rockwell Hardness Test
The Rockwell Hardness Test is one of the most common methods for determining the hardness of a steel. The test measures the penetration depth of a diamond body in the steel. And the corresponding hardness is automatically determined by a comparison procedure.
Tip: As a customer, you are rarely able to accurately check the hardness of a knife. Ask about a knife's hardness at the time of purchase.
The grinding operation
At GIESSER, blades are ground on state-of-the-art machines in a fully-automated process.
It is important to ensure that the blades are very well cooled (using plenty of water), precisely the same grinding angle is maintained and the grinding pattern is extremely fine and consistent.
Tip: Serrated knives cannot be re-sharpened by hand. Ask your specialist dealer or contact us.
Tip: Make sure that the blade does not overheat when being mechanically re-sharpened. This will alter its structure. The hardness will reduce and the cutting edge is no longer retaining.
aw – partly serrated edge
The serration is about 4 cm long and easily cuts through even the hardest plastic sausage casings.
w – wavy edge
The regularly grinded waves along the cutting edge enable the knife to slide securely and without slipping through hard hides and crusts.
wwl – scalloped edge
A knife with scalloped edge slides more easily through the cutting medium. The result is a perfect and effortless cut.
z – serrated edge
Suited for the cutting of fruit and vegetables with hard skin. The blade slides effortlessly through the skin without damaging the flesh.
The steel processed by GIESSER is made in Germany, Austria and France. A high-alloy, rust-resistant steel to DIN 1.4110 and 1.4116 is used in the vast majority of cases.
The main components are:
- Carbon (C): determines edge retention and sharpness, proportion: 0.50 – 0.60 %
- Chrome (Cr): increases the rust resistance of the steel, proportion: 14 %
- Vanadium (V): increases the strength of the material, proportion: 0.1 – 0.2 %
- Molybdenum (Mo): helps improve rust resistance, proportion: 0.5 – 0.8 %
By their very nature, knives and their accessories come into direct contact with food. GIESSER makes absolutely sure that the only materials used are those which meet the legal requirements for hygiene and food safety. It also arranges its own tests that substantiate conformity with the legal requirements.
Knives with wooden handles are an exception here. These knives must not be used for industrial purposes. They are, however, suitable for domestic use. As with all knives, very thorough manual cleaning after use is highly recommended.