Productivity improvement is the need of current market and manufacturing sector globally and machining time plays a very important role in reducing cost and time. In this book author aims to study the various factors affecting the NC machining time estimation and also tries to study the available methods used for estimating it. Hence a new prototype feature based model has been developed for NC machine time estimation. This model is then compared with the existing commercial software and other time estimation methods. The experimental data indicate that the proposed feature based model is reliable, practical and feasible. NC machining time estimation is a critical factor considered for manufacturing process planning and scheduling. Based on this time estimation process engineers can design and develop optimum design of products to reduce the manufacturing cycle time and hence reduce manufacturing costs.