Abstract: A blade for a comminution machine includes a first attack face facing in a first direction to perform comminution when the blade is rotated about an axis of rotation in a first direction. The blade also includes a second attack face facing in a second direction to perform comminution when the blade is rotated about the axis of rotation in a second direction substantially opposite to the first direction. A radial exterior of the first attack face and a radial exterior of the second attack face are connected along an arc subtending at least 30 degrees and less than 110 degrees with respect to the axis of rotation.