To facilitate the manufacturing of an end mill, this paper presents a manufacturing model of a flat-end mill using a five-axis computer numerical control (CNC) grinding machine. Using input data of end mill geometry, wheels geometry, wheel setting and machine setting, the NC code for machining will be generated directly from a solid modeling then used as input to simulate the end mill machining in 3 Dimension before machining. The 3D simulation system of the end mill grinding is generated by VBA and AutoCAD2008. Machining simulation consists of a sequence of Boolean operations on difference between the tool and the grinding wheels through NC code. Then the major design parameters of a cutter, such as relief angle and inner radius, can be verified by interrogating the section profile of its solid model. The manufacturing model presented in this paper provides a practical and efficient method for developing CAM software for the manufacture of an end mill.