Copper Ore Crushing, Grinding & Flotation - 911 MetallurgistMay 22, 2017 . Grinding and Flotation. Fine ore at minus 19mm (¾”) sizing is fed at a controlled rate into the open-circuit 2600mm x 3960mm (8'-6 x 13'-0) Hardinge rod mill at an average feed rate of 2,106 STPD or 87.75 STRH. Rod mill discharge at a nominal size of minus 16 mesh and a pulp density of 75 percent solids.amount of feed to rod mill when grinding copper ore,Evaluating the effect of feed particles size and their hardness on the .regarding changes in feed particle size distribution, size of the ball, speed of mill, prediction of energy . SAG mill; size of feed. 1. Introduction. The evaluation of grinding and breaking energy is usually criterion for the estimation of ore's hardness. On the other hand, the . Sarcheshme's copper mine located in Kerman, Iran.