Abstract This paper presents a new approach for the determination of cutting-force coefficients. The proposed methodology models a practical mechanism for collecting and analysing experimental data. The surface error is the measured parameter used for defining the cutting-force coefficients. The cutting tool deviation resulting from the cutting forces is considered as the main element of the surface error. The proposed mechanism consists of cutting two strips with the same cutting conditions but the axial depth of cutting differs with the height of the elemental axial disk. Hence, the resultant surface error represents the deviation of the cutter while cutting the strip with axial depth equal to the cutter elemental axial disk. The size effect has been taken into account when generating the functions for the cutting-force coefficients. Milling experiments have been conducted to verify the methodology and are reported in the paper. The proposed method overcomes the need to analyse and recalculate the instantaneous chip thickness, which is associated with the experimentally measured cutting forces traditionally used in the process of defining the cutting-force coefficients. The new approach provides the simulation process with instantaneous cutting-force coefficients, which are independent of the cutting operation geometry. The results when applying the new cutting-force coefficients show a good agreement between the predicted and measured surface error.