In many metal cutting operations, the relative displacement between the tool and the workpiece, determines the surface finish and the dimensional quality of the product. In an unstable operation, this relative displacement becomes bigger in an uncontrolled way and affects the cutting process. Vibrations of machine-tool systems leave a wavy surface in every tooth period. If waves on successive periods are not in phase, chip thickness may grow exponentially and cause an unstable operation. Having more than one cutting edge in boring tools can facilitate higher material removal rates and thereby boost productivity. Regenerative chatter vibrations, as a cause for instability in multiple-teeth boring operations, is investigated in this thesis. Different analyses for different types of inserts are presented. A method to approximate the uncut chip area is proposed to facilitate the frequency domain simulation. The proposed models were experimentally validated by cutting tests.