Linear motor direct drive actuators are implemented as feed drives for the end milling machining process. An H∞ optimal feedback controller is designed and analyzed for performance, stability, and robust stability. A simplified cutting process model is presented for use in system stability analysis. Because of uncertainty in the cutting process model and the multivariable nature of the system when cutting is taking place, a μ analysis approach is taken to establish stability boundaries for the machine parameters. Experimental results verifying the cutting process model, examining the feedback controller performance, and verifying the accuracy of the robust stability analysis are presented.