A machine operator asked the injured employee to change out an air tester. The employee asked another coworker to retrieve airlock seals to change the air tester. The coworker and machine operator went to the tool crib to retrieve seals. During this time, the injured employee reached into the area of operation. A sensor sent the jaw block (hydraulic-operated) down and amputated the employee's left-hand ring finger (half of finger) and pinky (1st joint of finger).