Thread cutting is a form of cutting process, and during the process, energy is transferred into the workpiece by the tool that generates the surface layer of the threaded part. Cutting conditions are heavier in thread cutting than cylindrical side cutting operations, and energy consumption is more important at the thread root during thread cutting. Total cutting energy is mainly affected by cutting forces and cutting velocity. Variation of cutting forces, chip thickness ratios, and shear angles in thread machining were investigated. Effects of the thread height and tool wear on the chip compression ratio were determined experimentally. Main cutting forces at the thread root were calculated by using Zorev's force calculation approach to evaluate the cutting power and specific cutting energy during thread cutting process. Fatigue strengths of threaded specimens produced by machining were evaluated depending on the cutting power and specific cutting energy at the thread root. It is observed from the experimental results that when specific cutting energy is increased, fatigue strengths of the threaded specimens are also increased significantly, while cutting velocity and chip thickness are kept constant in the specified range.