Abstract: The phenomenan of negative shear and its influence on the destruction of cutters are further studied. It is proved that the negative shear which results in the curly cutting scrap rotates on the cutting chin and makes the strees distribution worse at the outer wedge is the primal cause of the cutter destruction, by means of high speed picture and measurement of milling force variation at cut-out and analysis of elastic thoory. At last, the measures to decreases cutter destruction are proposed.

Key words: Destruction, Milling cutter, Negative shear