This research examines the amount of heat transmitted to the workpiece during the end milling of aluminium alloys. The thesis covers the development of a mathematical model to predict the temperatures in the workpiece being machined by end milling. The model uses the proportion of the cutting energy that is transmitted to the workpiece as a major variable. The mathematical model was used to predict temperature distributions within the workpiece for a wide range of cutting speeds and feed rates. A technique for measuring the workpiece surface temperatures using an infrared thermometer mounted on the milling machine quill was developed. At present no commercial method for measuring temperatures while machining exists. The methods of machining temperature measuring temperatures while machining exists. The methods of machining temperature measurement that have been used in laboratories have been proof of concept and were not designed for industrial use. All this emphasises the need for a reliable method of measuring temperature at the required point, and a definition of that point. The method developed is capable of presenting data to the machine operator simply and accurately in real time.