Impact mills, PH series are extremely sturdy machines that can also be used as primary machines. They are suitable for crushing not very abrasive limestone. They are designed to produce aggregate 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 are fixed by means of a retainer bar and a locking wedge, which secure the hammers rigidly. Hammers in manganese steel, internal side armours made of manganese steel plates fixed using conical bolts, impact walls with manganese steel bars complete the equipment. PH series mills are supplied complete with a hydraulic system to open the machine and adjust the lower impact walls as well as a hydraulic anti-clogging system.