In an orthogonal cutting process, the shear plane has a significant force resulting from chip removal action, since in the chip removal process, most of the force applied to the workpiece is used to change the shape of the material in the form of heat and it is dissipated by the chip, tool and the workpiece. It can be seen that the shear zone takes the highest temperature during the chip removal process. Therefore, increasing or decreasing the area of the shear plane and its angle has a direct effect on reducing the temperature and force resulting from chip removal and accordingly, improving the cutting conditions. In this research, the effect of machining parameters including cutting velocity, depth of cut, rake angle, and tool radius on temperature, force, and angle of cutting plane in AISI 4340 alloy is studied. The two-dimensional finite element model of orthogonal cutting is simulated as a couple of dynamic-thermal loads. The results obtained from the simulation in DEFORM software show that the depth of cut has the greatest effect on the changes in the angle of the shear plane in such a way that increasing the depth of cut decreases the angle of the shear plane and vice versa, also, the radius of the tool has the least effect on the changes in the angle. The results obtained from the numerical simulation are in good agreement with metal-cutting theories.