The results of research are presented whose objective was to develop a remote thermocouple technique for measuring cutting temperatures in a turning operation. The measuring scheme relies on the signals from two standard thermocouples located beneath the cutting tool insert. These signals are fed into an analog computer which calculates on-line the temperature at the tool point. The on-line computation provides an estimate of the tool point temperature within about one second rather than requiring the tool thermal system to come to steady state before temperatures are estimated. The research included two development phases. The first involved the use of digital computer simulations of the heat transfer process in a generalized cutting tool. This led to the derivation of a simple equation to estimate the cutting temperature from measurements taken at two remote points. The second phase concerned experimental validation of the computer simulations under a variety of cutting conditions.

An analytical study of the effect of crater wear on the response of a remote thermocouple sensor is described. The remote thermocouple sensor is at present being developed as a device for the on-line measurement of tool wear. This technique depends for its operation on the strong influence of wear on the transient temperature variations in the tool. The two-dimensional transient temperature variations in the chip and tool regions are determined using a numerical finite-difference technique. Results are obtained under idealized cutting conditions with a zero wear rate, a normal wear rate, and an accelerated wear rate. Comparisons are made between the three cases to develop relationships for the effect of wear on the temperature at the remote thermocouple location.

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Experimental data. are presented which demonstrate a strong correlation between tool wear and the signal of a thermocouple located at a position on the cutting tool remote from the cutting edge. A mathematical model is proposed for explaining this relationship between tool wear and. temperature. The model is supported by good statistica.! agreement between the data and the form of the proposed equation. For Q total of nine different machining conditions with replications for several of the conditions, the correlation coefficient ranged in vsJue between 1),837 and 1),978. IntroductionSince about 1962, there have been a number of attempts to develop relationships between tool wear and other process variables in metal cutting. The motivation behind these efforts has been to determine a scheme for estimating tool wear while the cut was in progress. Work sponsored by the United States Air Force at the Bendix Research Laboratories (1964) led to a proposed tool wear rate expression based on measured values of metal removal rate, cutting temperature and torque rate of change. Another study was based on the use

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