For CNC machine tools, in the beginning of the processing to determine the relative position of the tool and the workpiece is very important that the relative position of the knife-point by confirming to achieve. Knife knife point is determined by the relative position of the tool and the workpiece reference point. Knife point can be set on the part to be machined, may be provided in the fixture and parts locating datum has a location to contact a certain size, the knife-point processing is often the origin of the parts. Knife point selection principles are as follows:
(1) of the selected point of the knife should make programming simple;
(2) the point of the knife should be easy to find a positive choice, easy to determine the origin of the parts machining position;
(3) The location of the point of the knife should be easy to test in the processing and reliable;
(4) the choice of the point of the knife should help to improve the machining accuracy.