Though it is very difficult to model physical phenomena of machining exactly, results trend could be re-considered from a perspective of the tool geometry. In this paper, machining tool tip was considered as a cantilever beam attached to the shank, and assumed to be deformed by uniform stress as shown in Fig. 7. Shank was assumed as a rigid and fixed body, during the drilling.Since only a partial parts were drilled into the work piece in practical machining, load w was assumed to be applied in length of b.Real values for b in the experiments were 5.25-mm for 0.25-mm tool, 6-mm for 0.3-mm, 0.4-mm, and 0.6-mm tools. Deflection at the tool tip, ı could be calculated using Equation 1 below [31].