An Intelligent Tool Post (ITP) used in lathe is proposed in this study. ITP is designed from the basis of two different cutting force characteristics produced from abnormal cutting generated by tool crashing workpiece and from normal cutting. ITP is capable of sensing and distinguishing the normal cutting signals from the abnormal ones. During normal cutting, ITP is able to resist the cutting torque and continue the cutting. As abnormal cutting occurs, the tool would move away from the workpiece without any damage. The equations for design and operation have been established. With the threshold and the design equation, one can design appropriate ITP. The threshold can be calculated and set up by the operating equation and the cutting conditions. Furthermore, Taguchi method was employed to conduct the experiments and analyze the experimental results. The results showed that the ITP's functions met the design requirements completely.