The production of sago starch involves multiple processes, and grating is among the important processes since it indirectly affects sago starch recovery. In order to produce a finer size of grated sago and high starch recovery, a new design of sago disc grating machine has been developed. An optimization was performed to determine the optimum operation conditions on the basis of the feeding rate and grating speed input of the sago disc grating machine with the starch recovery as the output. The grated sago was dried and sieved at different sizes to determine the size distribution. A mathematical model was developed to predict the starch recovery using Minitab 9.1.0. software. The optimum feeding rate was 0.1 m/min with 1,500 rpm of grating speed to produce 23.57% of sago starch. This study showed that the feeding rate and grating speed affects significantly the size of the grated sago (P < 0.01) and indirectly affects starch recovery. Overall, the optimization process is very important to ensure that the output is at the maximum level.