ABSTRACT
This chapter develops a wear mode hypothesis. The stresses at which the asperities of the rock fail are related to rock material properties (among other parameters), as are the cutting forces. With an increase in the displacement rate of the cutting tool into the rock, the stresses will increase until the rock relief fails. At this point, a change of cutting mode and wear process or wear mode takes place. Resistance of rock material to cutting or cuttability of rock may determine the magnitude of the cutting forces: the shear or cutting force and the normal force. Rock material properties such as strength, stiffness and hardness among others determine the resistance of rock to cutting. Interaction of cutting tools during the cutting process reduces the cutting forces dramatically. The interaction depends on the spacing and cutting depth of the tools. Rock shows a higher strength with an increase of the rate of loading of the rock.
