Tool abnormality detecting device

A tool abnormality detecting device for a machine tool for machining a work with a machining tool selected according to a machining program, said device comprising:

• machining load detecting means for detecting a machining load during machining with the machining tool;
• memory means for storing threshold data for judging a tool life, detection starting time data and detection time data, for each machining stage carried out by each machining tool according to the machining program;
• and
• a comparison/judgement means for judging abnormality of the tool by taking detection data corresponding to the machining tool from said memory means and comparing the output of said machining load detecting means with a threshold in said threshold data within a detection time set in said detection time data,
• wherein each threshold has an upper and a lower limit, and wherein the abnormality is determined by said comparison/judgement means based upon actual cutting power, said actual cutting power being determined by subtracting a power of a motor of the machining tool while not in a machining operation from a power of said motor during machining.