The roundness and surface roughness are important quality performances for machined round parts. In order to get the best quality performance by less experiment search for optimum parameters, an orthogonal array was used for the experimental design, optimal machining parameters were determined by the grey relational grade obtained from the grey relational analysis, and the main machining parameters that affect the machining performance can be found by the difference between the maximum and minimum value of the grey relational grade of the machining parameters. Experimental results have shown t...