An employee placed a mast platter (aluminum disc) in a vise inside a CNC machine and programmed the machine to mill the top so that it was level. A tool used to level the mast platter became caught on a drilled hole. The employee went to stop the machine when the mast platter became airborne, broke through the closed CNC machine plexiglass door, and struck the employee on the abdomen. The employee sustained a laceration to the left side of his abdomen.