Cheap is not always economical – Quality knives instead of expensive, cheap knives

Hollow knife, cutting crowns, plan blade or reversible blades

Whether you are looking for hollow knives, cutting crowns, flat knives or reversible knives – the market for shredder rotor knives offers an abundance of cheap knives. These knives are often made from economical materials less suited for cutting tools, such as CK45, for example, which is only surface hardened. The service life of these knives is extremely short and their cost-effectiveness therefore very poor in the majority of cases.

PR-Technik GmbH, Germany, specialises in developing, manufacturing and selling industrial knife systems, relying entirely on premium quality: the hollow knives or cutting crowns in the PR-Technik range are provided with a 1.5 mm thick, hardened surface, a moderately hard transition zone and a soft core. They are manufactured from high-quality steel, specially suited to case hardening, and achieve optimal hardness by repeated tempering. The high-quality of PR-Technik knives comes into its own with regard to applications in which the knives are exposed to impurity-related, sudden forces and loads, in particular.

The differences compared to cheap, 1.2379 tool steel knives, can be even more significant. It is common practice for the majority of rectangular knives to be produced from a rolled, square steel section. In terms of material and production costs, this production method is comparatively economical, but presents a significant disadvantage as a result of rolling (banding): The forces acting on the knives during the shredding process act in exactly the same direction as the fibre (cf. Figure 1). This results in a considerably higher knife fracture hazard.

PR-Technik GmbH's hollow knives, cutting crowns, flat knives or reversible knives, in contrast, are always produced from the more expensive flat steel bar. In these knives the cutting forces act perpendicular to the fibre with the result that the fracture hazard is very substantially reduced (cf. Figure 2). In addition, the optimal heat treatment with multiple tempering processes brings the knives to the ideal hardness, positively impacting on the cutting force and the throughput capacity.

Buying cheap knives, then, only has merit at first glance. In economic terms the investment in expensive, but high-quality, knives is far more economical, simply because they have much higher service lives per cutting edge. This results in noticeably lower knife replacement and time-consuming, expensive machine standstill times are distinctly minimised.


More than 20 years experience in shredding technology and intensive collaboration with machine manufacturers and operators in the timber, plastics and recycling industries create impetus towards new, innovative products, opening the way to greater efficiency and profitability. PR-Technik GmbH develops and produces high-quality industrial knife systems for customers around the world, in Germany. Our aim is to provide individual solutions and adaptations for all customer-specific tasks.

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