In this paper, an initial investigation of the nonlinear dynamic properties of clamped boring bars is carried out.Two nonlinear, single-degree-of-freedom models with different softening spring nonlinearities are introduced formodeling the nonlinear dynamic behavior of the fundamental bending mode in the cutting speed direction of aboring bar. Also, two different methods for the simulation of nonlinear models are used. The dynamic behavior interms of frequency response function estimates for the nonlinear models and the experimental modal analysis ofthe clamped boring bar is compared. Similar resonance frequency shift behavior for varying excitation force levelsis observed for both the nonlinear models and the actual boring bar.