1) 12 dia end mill run instead of 10 dia.|2) Tool number entered in the program was wrong.|3) The program has two sub sequences one is for semi finishing and the other is for finishing but the tool used for both the operation was same so the operator changed the tool number for the semi-finishing operation and did not changed for the finishing operation.|4) Usually the programs were run separately but to reduce the cycle time the program was merged and the operator did not cross checked the program before starting the cycle.