3) Analysis results with the developed model show that temperature inside the probe was around 440˚C at the center of the top surface and 400˚C at the probe root. Calculated temperature distribution proved that the measured temperature with the thermocouple at the probe tip is almost the same as the surface temperature. On the other hand, the shoulder had a steep temperature gradient along the tool axis, and thus the measured temperatures inside the tool were different from the surface temperatures by about 40˚C to 50˚C. It showed that the shoulder surface temperatures are higher than temperatures measured with thermocouples.