Separator disc is used in a disc separator for separating a mixture of grain according to particle length. It is characterized by a series of spaced parallel discs, which is mounted for rotation on a common shaft. The discs are submerged in the mixture. Pockets in the exposed plane surfaces of the discs lift shorter grains from the mixture and dump them as the discs rotate to separate the particles. It is formed as a castable polyurethane material.