The number of hammers used for a hammer mill of 1,800 rpm, should be 1 for every 2.5 to 3.5 horsepower, and for 3,600 rpm, one for every 1 to 2 horsepower. ... Freezers - Feed Machinery & Equipment; Extruders for Feed Production; Pellet Feed Dryers . Featured Hammer Mills. Champion Series Hammer Mills. SFSP 132 Hammermill.