If the three force components Fc, Ff and Fd are measured, and resolved into components in the plane of, and normal to, the rake face of the tool, hc can be obtained from the condi-tion that the chip flow direction is opposed to the direction of the resultant (friction) force in the plane of the rake face. ae can then be determined from hc and the tool geometry. Equation (6.17a) can then be used to determine fe from the measurement of chip thickness. When the chip thickness varies along the cutting edge, a modification of the equation must be used