In most machining operations undersirable burr or negative burr is created at workpiece edges. The burr/negative burr formation mechanism is analyzed based on shear strain which is obtained from simulation results of the finite element model of burr/negative burr forming process. To varify the simulation results, experiments are conducted. We observered that there exists a critical value of shear strain for burr/negative burr transformation. Burr or negative burr, which to be formed at workpiece edges can be controlled by adjusting the cutting conditions or tool geometric parameters. Edge quality of workpiece can be controlled by converting burr or negative burr forming.