Abstract: A blade sharpening device for a rotatable chopping cylinder for a forage harvester or the like, which cylinder has a plurality of circumferentially spaced and generally parallel blades that are of a generally spiral shape. A carriage moves along parallel to the cylinder and has a sharpening tool extending from it for contact with the blades. Guide means are connected to the carriage and roll along the surface of the blade being sharpened whereby as the carriage moves along the axis of the cylinder a grinding wheel may be maintained in alignment with the blade. Biasing means are provided to maintain a torque on the cylinder and to maintain that blade in contact with the guide means for proper relationship with the grinding wheel.