During single point diamond turning, the effects of tool feed rate on surface figure and finish of aluminium-6061 alloy are evaluated. The studies are conducted on 60 mm diameter optical flat surfaces. Twenty-s ix specimens are diamond turned for varying tool feed rates (0.3 μm/rev to 30.0 μm/rev) keeping all the other machining parameters constant. The aluminium surfaces thus machined, show a typical roughness of 15 nm, and surface figure of better than a half wave peak-to-valley (PV) for optimum tool feed rate. The tool feed rate between of 1.5-8.0 μm/rev is found to be optimum for a given set of other machining parameters to get the acceptable surface figure as well as roughness values. An empirical formula with best fit has been formulated to find out the practical roughness achievable for the machining conditions under study.