Abstract: The normal course of operating a numerically controlled machine tool includes the automatic collection of significant event data without any special interaction by the machine tool operator. These events are of two types: those embedded in the machine tool part program, which may be ordinary program steps or special event markers; and those which represent operator intervention of the programmed process operating on the machine tool. The theoretical time for the occurrence of the programmed events is embedded in the machine tool part program. The identity, date and time of the actual occurrence of an event is stored in nonvolatile memory. This technique may be used in a single computer controlling one or more machine tools or in a network with a host computer serving as the event depository and as the source of machine tool part programs. The event records are available for analysis to improve the productivity of the operation.