An employee was sitting on a casing head valve to hold himself up while working in a cellar. He was holding onto a stud with his left hand for support. He was cutting approximately 14 inches off of the casing using a torch when the blowout preventer became off-center and shifted to the side. His left index, middle, and ring fingers were then caught and smashed between the stud and casing, requiring surgical amputation of two fingertips at the base of the nail and one fingertip at the first knuckle.