A tool for insertion of a sensor to a predetermined depth within a bore includes an elongate tool tip terminating at a tip end, a handle affixed to the tip, and an axial passageway extending through the tip and handle to a tool end. A window is provided extending transversely into the tool tip at a location between the tip end and the handle and provides visual access to the passageway. The tool is capable of use in two modes of operation. In a first mode, a bore is drilled into an object body such as a tire to the required depth. The sensor leads are fed through the tip of the tool and pulled through the handle until the sensor touches the tip of the tool. Thereafter, the tip of the tool with the sensor is inserted into the pre-formed bore. The tool tip is then removed out of the bore, leaving the sensor within the bore at the pre-determined desired depth. In the second mode of operation, the tip of the tool is inserted into the pre-drilled bore and a thermocouple is inserted into the bore via the axial passageway extended through the tool tip and handle. The progress of the thermocouple insertion is tracked through the window. A marking or other indicia may be placed on the trailing leads of the thermocouple at a predetermined spacing from the thermocouple. Visual identification of the arrival of the indicia at the tool tip window indicates a successful insertion of the thermocouple to its intended depth. Thereafter the tool tip is removed, leaving the thermocouple within the bore at the predetermined, optimal depth.