TOOL ABNORMALITY DETECTING DEVICE IN MACHINE TOOL

PURPOSE:To detect an abnormality of a cutting tool with a high degree of accuracy, by providing, on a plate member capable of transmitting AE waves, an AE sensor and an opening which is approachable surrounding a spindle, and by attaching the plate member to the machine body with the opening being approached to the spindle. CONSTITUTION:When AE waves are generated due to an abnormality of a cutting tool 5, the AE waves are directly transmitted from a cutting tool 5 to a spindle 11 carrying the tool 5, and are then transmitted to a plate member 10 through an opening 12 so that the transmitted AE waves are detected by an AE sensor 9. Since the AE waves substantially directly transmitted from then cutting tool 5 may be detected, no noise and damping caused by bearings occur, and further no affection due to the shape of a workpiece is effected. Thereby, either of breakage, chipping and friction may be all detected at a high S/N ratio with a high degree of accuracy, and therefore, it is possible to detect an abnormality of the tool with a high degree of accuracy.