In forage harvesters, drum devices equipped with fixed blades are used to shred mowed plant mass. The length of the shredded particles is determined by the number of blades and the diameter of the drum. While flat blades are easy to manufacture, they can cause uneven loading when installed parallel to the drum axis. Angled or helical blades are more complex to manufacture but offer solutions to this issue. Using a sectional drum to arrange blades can help minimize impact loads. Additionally, helical knives, which are outlined along a helical line, offer a solution by providing a constant cutting angle and even loading. However, they are more complex to manufacture. This research focuses on designing a helical knife to optimize the shredding process based on specific geometric parameters. Parametric equations for the knife surface are formulated, and an approximate unfolding is constructed due to the non-developable nature of the surface. Calculations are based on given geometric parameters to optimize the shredding process. For the given parameters τ = 20°, φ = 65°, R = 0.25 m, L = 0.72 m, and uo = 0.1 m, the flat blank of the knife will be a part of a ring, which is determined by the central angle ψ = 0.08 rad and bounded by the arcs of circles Ro = 9.55 m and ro = 9.45 m.