ABNORMAL TOOL CHANGING METHOD

PURPOSE:To make unmanned operation performable, by setting a tool malfunction detecting sensor down to an air pressure changing system, and stopping a machine tool when a pressure switch is operated by a variation in air pressure, while operating an auto matic tool changer at once. CONSTITUTION:In machining a work 3, if rotation slippage is produced between a tool setting shaft and a tool holder 12 due to wear or the like in a cutting tool 22, injection air out of an injection nozzle of the tool 12 is stopped or air injection is started or the like whereby air pressure in a hose 16 is varied to some extent, so that this variation is detected by a pressure switch 17, transmitting it to a control panel 20 via an optical fiber cable 19. And, this control panel 20 stops a spindle motor 7 on the basis of this signal, while it operates an automatic tool changer 11 and the worn tool is automatically changed with a new one in a tool magazine 8. Afterward, machining is reopened from the work stopping position. Thus, unmanned operation for hours by a maching center or the like can be made possible.