Experimental results on plastic strain induced in truning operation are presented in this paper. The plastic strain is computed by lagrangian strain using grid method, and metal cutting phenomena are also illustrated by micrograph and distribution figures of plastic strain and microvickers hardness of the machining surface. In the cutting of ductile materials, such as carbon steel, generally, the plastic strain is found to be concentrated near the surface. The amount of plastic strain increases with increasing cutting speed and feed rate. The dustribution of microvickers hardness is greater near the cutting surface and decreases from the machining surface under which its hardness returns to the normal hardness of the material.