This thesis presents the underlying mechanisms for the occurrence of surface anomalies in turning of difficult-to-cut materials with high-pressure coolant supply. Based on empirical and analytical investigations of each type of surface anomaly, the cause-and-effect relationships between the relevant process parameters and the surface quality were identified, translated into an explanation model and validated in a case study. Finally, an overview of different possibilities for anomaly-free machining with high-pressure coolant supply were discussed.