Machining is the most widely used and efficient material removal process, and tool wear in machining is usually of great interest in order to improve machining efficiency and effectiveness. Cutting tool wear patterns such as the flank and crater wear and the dead metal zone (DMZ) may induce the cutting tool geometry variation in machining. As a result, cutting forces may increase or decrease due to the change of tool effective cutting geometry during machining operations. A quantitative understanding of and the ability to predict cutting forces in relation to tool wear are important to the tool life estimation, chatter prediction, and tool condition monitoring. Most available force models are limited to fresh tool conditions or worn tool conditions only considering the flank wear. Furthermore, the effect of DMZ on cutting forces, especially when a chamfered tool is used, is frequently ignored. The objective of this dissertation is to analytically model the combined effect of the crater and flank wear as well as the effect of DMZ on cutting forces in 2D and 3D turning.