Tool Geometry:

Back rake angle might vary over a wide range (namely, from + 20° to - 15°) and its value for a specified tool is decided based upon the kind of workpiece material being machined. This is observed that as the back rake angle enhance in the +ve direction the cutting force reduced but as the back rake angle reduced (below 0°) then the cutting force increases (Figure 7). In other terms, as the back rake angle reduced, the cutting force enhanced. But, as the back rake angle enhance (in +ve direction), the tool becomes weaker to withstand the forces. Therefore, it may not be enhanced beyond a certain value, else the tool becomes too weak to work like a cutting tool.

Figure 7 : Effect of Back Rake Angle on Cutting Force, Fc

Plan approach angle (φ_p in Figure 10, unit 7) and nose radius (r) jointly influence the cutting force acting upon the tool. In specific case of a tool with r = 2 mm, a minima is observed while in case of r = 0 mm the force F_c reduced with the enhance in plan approach angle, φ_p  (Figure 8).

Influence of nose radius on F_c, F_f and F_d are illustrated in Figure 9. A enhance in tool nose radius enhance deformation and therefore larger force F_c. Force F_d is also enhanced however F_f is reduced.