An employee was attempting to restart a cooker's infeed screw. After locking out the equipment, he tried to pull the belts backward to get the screw motor to turn over. He then attempted to start the equipment. When the equipment started, the motor turned over and the belt caught his glove, causing his left index finger to contact the belt/pulley. His fingertip was amputated. The machine was unguarded at the time of the incident.