Internal turning or boring operation is a common metal working process that is usually associated with vibration problems. Vibration problems in internal turning considerably influence important factors such as surface quality, productivity, production costs, etc. In this paper we report analysis results from an operational modal analysis of a boring bar during cutting operation. The results are compared with operating deflection shape results and traditional modal analysis results of the same boring bar. Results show that the first bending modes in the directions of cutting speed and cutting depth are active in the operating vibrations. The three analysis methods result in similar conclusions.