Boring depth is limited by the overhang on which the vibration frequency depends. To improve the process, a passive boring bar with dynamic vibration absorber has been used, but is effective only for a limited length of overhangs. In this study, a tunable damped boring bar was devised to cope with a variable length of overhangs. Vibration parameters arising from the various overhangs were analyzed using Euler’s beam theory. The proposed bar contains a cantilever-type dynamic vibration absorber to suppress the vibration amplitudes of the overhangs. The absorber adjusts the natural frequency of the bar by adjusting the spring stiffness. The proposed bar was fabricated and tested by impact excitation and its capability to suppress vibration was demonstrated.