Abstract: On August 3, 2005, an employee was milling a piece of 0.25 in. thick aluminum plate approximately 3-in. by 3-in that was clamped to the machine vise. As the head cutter of the cnc machine came in contact with the aluminum plate it pulled it out of the vice causing it to spin and ejecting it through the safety glass door. The employee was standing in front of the safety door, when the 0.25-in. plate came out of the vice and through the safety door, striking the employee in the chest. A coworker that was working near the employee heard a loud bang and turned around to see the employee lying on the floor. The coworker went to assist the employee and called his supervisor. The emergency medical services were called, and the local fire department arrived to provide first aid. The employee was transported to the Sutter Roseville Hospital and spent two days for treatment for a punctured lung.