milling 101 When you have almost forty years of data testifying to the extreme hardness of an ore and you then take a chance on installing a marginal 34 foot SAG rather than the more expensive initial capital cost 38 foot one you are then constrained by the ore, fogiving ore you make budget tonnage, hard ore you are lucky to maintain 800 tph so what do you do. Secondary crushing is one expensive way to correct the problem and share the burden of size reduction I guess but it sure makes one wonder about that original decision.