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