MIG series hammer mill with grid bars is a robust and reliable piece of equipment suited for the third crushing stage of non-abrasive aggregates especially limestone, capable of producing calibrated sand. Equipped with a flange-type rotor, with free hammers in manganese steel, internal armours made of manganese steel plates and anti-wear grid. The machine operating principle is based on the impact effect of weights rotating at high speed, the material to be crushed is hit by the hammers and thrown against the top armours. The parts of the material, which have not been reduced to the required dimension in this first phase, are held back by the grid, placed on the bottom of the machine and brought back by the hammers into the crushing cycle. This type of mill can produce high outputs, a bigger reduction ratio compared to other types of mills, a high percentage of fines in the size distribution curve of the output material and with a controlled maximum size of the produced material.