This chapter presents results on the design and experimental implementation and testing of robust controllers for the high-speed milling process for the purpose of avoiding chatter vibrations. Chatter vibrations are intimately related to the delay nature of the cutting process inherent to milling and should be avoided to ensure a high product quality. A design approach based on μμ -synthesis is used to synthesize a controller that avoids chatter vibrations in the presence of model uncertainties and while respecting key performance specifications. The experimental validation of this controller on a benchmark setup, involving a spindle system including an active magnetic bearing, shows that chatter can be robustly avoided while significantly increasing the material removal rate, i.e., the productivity.