Reversible impact mills, TH series, are machines suitable for crushing very hard and abrasive materials. They are designed to produce aggregates having the shape coefficient (polyhedral) required so the final product can have the mechanical properties required. These machines are equipped with an open type impeller, mounted on grease lubricated bearings that are protected by a series of labyrinth flanges. The hammers have an oscillating attachment system (TH M series) by means of a pin, or a fixed system (TH L series) by means of a retainer bar and a locking wedge, which secures the hammers rigidly. Protection devices, internal side armours made of manganese steel or alloy plates, double sector impact walls with manganese steel or alloy bars complete the equipment. TH series mills are supplied complete with a hydraulic system to open the machine and adjust the impact walls.