This research aims to develop a reliable machine for grinding the seashells in order to be used as cheap source of calcium supplements in poultry feed formulations. The developed mill was fabricated locally in Egypt based on the theory of grinding hammers that included a special fabricated roughness hammer knives. It is powered by a 40 hp electrical motor that could be driven through merged inverter to control its speed and load. The performance of the developed mill was evaluated under three experimental variables including; three different drum speeds (S) of 26, 39 and 52 m/sec ( 1000, 1500 and 2000 rpm); three concave hole dia. levels of 5, 10 and 20 mm; and three feed rate levels of 20, 40 and 60 kg/min. The performance evaluation of the mill included four measuring parameters namely: the particle size distribution (fineness degree FD, %); the machine productivity (P), the consumed electrical energy (EC); and the machine operating costs (C).The obtained results revealed that: the best fineness degree (FD), % could be achieved during setting the highest grinding speed of 52 m/sec (2000 rpm) at sieve diameter (D) 20 mm and feed rate (F) 60 kg/min, which produces the most needed diameters fits poultry supplements. However the optimum value of the machine productivity (P) was (3.30 ton/h) for the same setting .As well, the specific energy consumed (EC) was decreased from (15.93 to 5.08 kWh/ton) by increasing the drum speed from 26 to 52 m/sec and also increasing both feed rates from (20 to 60 kg/min)and sieve diameters from (5 to 20 mm) . Whereas, the minimum operating cost, (C) was (12.20 L.E/ton) by increasing the grinding drum speed to 52 m/sec for the inlet feeding rate of 40 kg/min and 20 mm sieve diameter.