A mechanistic modeling approach to predicting machining forces for grooved tools is developed. The models are solely based on the grooved tool geometry and the specific cutting energy and friction energy for flat tools. Special grooved tools (M2 grade HSS) were designed and fabricated and orthogonal cutting tests were performed to validate the model. The workpiece material used was Al 6061-T6. The force predictions from the model are found in good agreement with the measured forces. The effects of groove design parameters on the cutting forces are also determined.