Hey, I'm currently studying the mechanics of cutting (my reference is Serope Kalpakjian book about manufacturing). I found out that there are two main forces that are applied to the material (or chip) during cutting, which are thrust force and cutting force. I understand about the forces, their relation to the cutting angles (friction angle, rake angle, and shear angle), and how to adjust them. Unfortunately, I didn't find the minimum force required to actually cut (or shear) the material. Should I use shear or tensile yield strength of the material as a reference? Which force should I multiply with the cutting area (cutting depth x cutting width)? Is it the cutting force, or the thrust force, or both?
Thank you

P.S. I'm actually trying to design a plastic shredding machine and using the mechanics of cutting concept of a general machining process as an approach to calculate the plastic resistance during shredding.