Abstract: A tip for a cutting tool which can apply a heavy residual stress in compression to a material to be cut. This tip has four cutting portions. Each of the cutting portions has first and second rake surfaces having first and second angles of negative values, respectively, relative to an upper surface of the tip. Absolute value of the first negative angle is smaller than that of the second negative angle. The second rake surface is located further from a center of the tip than is the first rake surface, and is also located behind the first rake surface relative to a cutting direction of the tip.

Abstract: Method for predicting destruction of a rolling bearing using an apparatus which has a sensor for detecting acoustic emission signals from a rolling bearing, a plurality of band-pass filters which have different specific frequency pass bands within the range of 150-400 KHz, first comparators for comparing outputs from the band-pass filters with their respective reference values for the specific frequency bands, time-measuring devices for measuring time during which the outputs from the band-pass filters exceed the reference values, and second comparators for comparing the time measured with a further reference value. Of all signals detected by the sensor, only those that have frequencies of 150-400 KHz pass the corresponding band-pass filters, and then are compared with their respective reference values. The first comparators signal to the time-measuring devices when the outputs from the band-pass filters exceed the reference values.

Abstract: An apparatus for detecting a failure in a bearing has an acoustic emission sensor which detects acoustic emission from the bearing and outputs signals indicative of power of the acoustic emission, a bandpass filter which passes only signals in the range of from 100 kHz to 500 kHz out of the signals received from the aforementioned sensor, and a comparator which compares each of the signals in the range of from 100 kHz to 500 kHz extracted by the bandpass filter with a predetermined threshold value and outputs event signals each of which expresses that the signal from the bandpass filter exceeds the threshold value. This apparatus also has a computer which receives the event signals from the comparator, determines time intervals in which the event signals occur, totals the number of event signals for respective timer intervals, and determines whether or not the number of totaled events exceeds a predetermined threshold value to determine a failure in the bearing.