Abstract: A high speed machining controller comprises an acoustic emission sensor which is installed in or near a machine for machining a work piece in a high speed and which detects acoustic emission generated during machining a work piece; a signal processing means which is composed of a band-pass filter for passing an element of a frequency band corresponding to the acoustic emission by inputting a signal outputted from the acoustic emission sensor, a rectification circuit for rectifying a signal outputted from said band-pass filter, a peak detection circuit for detecting peak values of the signal outputted from the rectification circuit, and a smoothing circuit for smoothing output signals of said peak detection circuit and for outputting a signal corresponding to the amplitude of the acoustic emission for the purpose of processing the output signal of the acoustic emission sensor to detect its amplitude; a cutting condition discrimination means for judging the cutting condition of a work piece by comparing a detec

Abstract: An apparatus for discriminating a machining state from a non-machining state in a machine tool wherein a workpiece is machined with a cutting tool or grinder, comprising plural vibration sensors including at least one acoustic-emission sensor, which detect vibrations of different frequency bands, respectively, which are produced during machining of the workpiece by the tool. A discriminating device judges that the workpiece is being machined by the tool when levels of output signals generated from at least two of the vibration sensors are higher than respective predetermined threshold levels, and judges that the workpiece is not being machined by the tool when the level of an output signal generated from less than two of the vibration sensors is higher than a predetermined threshold level. Also disclosed is a method for discrimination between the machining and non-machining states.