OPERATION CONTROL DEVICE FOR FEED SHAFT IN MACHINE TOOL

PURPOSE:To continue work as long as possible even when working load is too large by providing the operation control device with a working load detecting means and a feed control means for diving a clamping member and a tool fixing member in their approaching directions. CONSTITUTION:A spindle motor servo amplifier 22 for controlling the rotational speed of a spindle motor 16 is connected to the motor 16 and a speed command circuit 23 and a spindle current detecting circuit 24 to be a working load detecting means are included in the servo amplifier 22. When the circuit 24 detects overload, a feed shaft control part 28 devices a driving means 26 reversely to the time of working to separate the clamping member from the tool fixing member 16, and after temporarily reducing the working load, joins both the members to continue the work. Thereby, even if the working load is abnormally increased, the work can be continued as long as possible.