Two new methods of measuring cutting temperatures have been evaluated. The first is a radiation technique using a lead-sulfide cell. The cell is arranged to sight through a small hole drilled in the work material sensing radiation from the shear plane and clearance face of the tool. Peak temperatures in these regions have been obtained but shear-plane temperature distributions could not be determined successfully. The second technique uses a 0.005-in. single wire imbedded in the side of a workpiece as a thermocouple. With orthogonal cutting the tool passed beneath the wire so that the wire passed up the tool face still imbedded in the chip. By this method it was possible to determine the temperature field throughout the chip and work. These temperature fields have been compared to theoretical predictions and show only fair agreement. The lack of agreement is due partially to the simplifying assumptions of orthogonal cutting and a true geometric shear plane necessary for theoretical solution. The necessity of locating the thermocouple junction on the side of the work introduced errors from side flow of the chip and certain other edge effects. The iteration procedure of Trigger and Chao has been extended to tools of any rake angle and simplified by use of a conducting-paper electrical analog.