This paper investigates the relationship between drill life, the sound, and the drift forces produced by the drilling process. Tests were performed while drilling steel with 38 in. twist drills. As a tool life criterion, the wear of the drill lips was monitored. Typical signals are described, and various signal processing techniques presented in view of characterizing them. These include time, frequency, and amplitude domain techniques. It is shown that specific signal patterns that occur with increasing lip wear show definite trends which can be followed by some analysis techniques. A discrete point process, derived from the signal’s spectrum, has been found specifically valuable. Results shown for actual data using these signal analysis techniques seem to support a theory of drill wear mechanism which was reported recently.

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