THE EMPLOYEE AND A CO-WORKER WERE ATTEMPTING TO DRIVE A BUCKET TOOTH OUT IN ORDER TO CHANGE A TOOTH. THE EMPLOYEE HELD THE PIN DRIVER AS HIS CO-WORKER USED A SLEDGE HAMMER ATTEMPTING TO HIT THE PIN DRIVER.THE CO-WORKER MISSED THE DRIVER STRIKING THE BUCKET TOOTH CAUSING THE EMPLOYEE TO BE STRUCK BY A METAL FRAGMENT FROM THE TOOTH.