Coupled with an optical fiber,temperature responses at the contact zone during grinding of granite and ceramics with a diamond grinding were measured using a two color infrared detector. It was shown that, compared to a single photocell system, the two color detector is able to measure not only the temperature, but also the corresponding apparent emissivity of the workpiece under the grinding conditions. Since the measured temperatures near the surface are somewhat higher than analytical results due to the holes for the optical fiber, the infrared system is suitable for measuring the temperatures at some distance below the workpiece surface. The temperatures on and near the workpiece surface can be calculated from the theoretical thermal model based on the ratio of energy conducted to the workpiece, which can be obtained by a temperature matching technique. The measurement of gridning temperatures is important for understanding the heat transfer at the tool workpiece interface since the energy partition value can be obtained based on the measured temperature.