Boring and Trepanning Association (BTA) deep hole drilling is often used to machine bores with large diameters (D > 40 mm) and a length-to-diameter ratio greater than ten (l/D > 10). Typically, the tool cutting edges on the BTA drill head are arranged asymmetrically. This results in radial forces that are supported by guide pads on the bore wall. This leads to forming processes on the bore surface and feed grooves are smoothed. In addition to improving the roughness, this also results in changes in the subsurface zone of the bore with regard to the microstructure, the hardness and the residual stress. In experimental investigations, the thermal load on the outer cutting insert and the guide pads is determined. The available sampling rate of a fiber-optic two-color pyrometer is used to achieve a high local resolution of the temperature measurements. Experiments were performed with the optical measurement fiber located inside the workpiece to determine the temperature at the cutting edge and the guide pads.