This study seeks to develop an efficient way of quantitatively investigating the intrinsic size effect in machining. This is accomplished by carrying out the following procedures: conducting the pure two-dimensional orthogonal machining with the cutting edge radius and the uncut chip thickness varied, investigating the relation between the cutting edge radius and the specific cutting energy when the uncut chip thickness is fixed, and then estimating the specific cutting energy for a perfectly sharp tool by extrapolating the relations obtained for different values of the uncut chip thickness. Finally, the usefulness of the developed method is validated by showing that the estimate of the specific cutting energy for a perfectly sharp tool can be effectively utilized for understanding and modeling the intrinsic size effect, especially the material length scale, in machining.