Accurately predicting milling forces is essential for assessing tool life and surface quality. In ball-end milling, which is primarily used for finishing operations, there is a critical need for a thorough investigation to optimize the machining process and cutting parameters. This research is vital for achieving greater precision and efficiency in milling operations. This paper presents an improved force model for ball-end milling that incorporates a new Instantaneous Uncut Chip Thickness (IUCT) model, which considers the engagement area between the tool and the workpiece. The IUCT model accounts for the effects of tilt and lead angles in ball-end milling. This approach captures the local impact of tilt and lead tool inclination on chip geometry, offering better precision than traditional models. For each individual cutting edge, the force components are calculated using a mechanistic method. The proposed model has been thoroughly validated through multi-axis milling experiments and compared with previous studies. The comparison demonstrates that the new model, based on IUCT development, effectively predicts milling forces, making it a valuable tool for optimizing tool life and ensuring high-quality surface finishes in ball-end milling operations.