The safe hidden trouble that numerical control lathe several easy to overlook Numerical control lathe in nc machine tool teaching, students training, numerical control lathe in practical operation there are some potential safety hazard, must be attention. 1, the background editing functions In FANUC series oi Mate TB in the system, the manufacturer in order to make the operator processing convenience, set the background editing functions, namely in the automatic processing process, but in the case of not terminate processing, the program edit mode for the current program edit modifications or other programs for the background; Also can choose to "the handwheel way" will control mode, by turning the handwheel making knives, so as to change the position of the processing centers. Background editing features convenient operator in the process of machining of parts manufactured by modified, simplify the operation process. But this kind of simplified, has brought a serious hidden trouble for safety operation, in the teaching practice, students frequently occur wrong operation. When the control mode selection to "automatic cycle", if the machine not clamping chuck