NC MACHINE TOOL

PURPOSE:To control the positioning of a main spindle by permitting the length of a tool fitted onto a main spindle to be correctly measured, in an NC machine tool equipped with a tool exchanger. CONSTITUTION:The transfer position in the Z-axis direction of the main spindle 4 of an NC machine tool is detected by the position detector 6 such as linear scale, etc., and the transfer position in the X-axis of a gate-shaped column 2 and the transfer position in the Y-axis direction of a saddle 3 are detected by other position detectors. A tool detection apparatus 31 is installed in the vicinity of the tool exchange position TCP behind an automatic tool exchanger ATC 12. After a new tool 16 is mounted onto the main spindle 4, it automatically measures the length of the new tool by an ATC12, and a tool file memory part 52 is rewritten. Therefore, the necessity of correctly setting the tool length from the start is obviated, and rapid setting of tool is permitted. Thus, the positioning of the main spindle can be controlled.