Internal sensors already available in the machine tools may prove to be an interesting approach to monitor the machining process. Accurate determination of the position of the individual tooth on a milling cutter is important to be able to correlate the measured responses from the machine tool position encoders to the tooth or teeth that may be the cause of the response.

The aim of the work presented in this paper is to develop a measurement method to identify the individual tooth on a milling cutter by their angular position relative to a specified 0-degree direction. If the lower and upper bounds of the cutting zone are known, together with the actual spindle position and the starting time of the cut, it will be possible to track and identify which teeth are within the cutting zone at a given time in the following off-line analysis of the responses. This may simplify the task of finding potential correlations between the state of individual teeth on the milling cutter with measured responses from various sensors during the milling process. The proposed method is based on a reflectance detector and uses accurate position information provided by the position encoders.

A validation of the measurement method is also presented which shows that the error of the estimated angular position is approximately +/- 0.15 degrees for the validation setup used in this case.