Signal processing system and signal processing method for cutting tool with abrasion sensor

For determination of the expiration of the life of a cutting tool on the basis of a resistance signal from sensor lines, a true signal component indicative of the abrasion of the sensor lines should be extracted from the resistance signal. In a signal processing method according to the present invention, an output of an abrasion sensor is sampled in a predetermined sampling cycle (Step S1), and then the sampled data is passed through a median filter for elimination of a noise therefrom (Step S2). Further, the noise-free data is passed through a separation filter (Step S3). By the separation filter, reduction data having a time-serially reduced in value is separated and eliminated from the noise-free data. As a result, true data indicative of a change in the resistance of the sensor is obtained. The true data is subjected to a counter function process (Step S4) thereby to determine how many sensor lines have been cut off by the abrasion. The expiration of the life of the cutting tool is detected when the number of the cut-off sensor lines reaches a predetermined number (Step S5).