Hammer Mill components operating principles types uses 05/07/2020· Hammer mills crush materials into two 2 stages 1 Size reduction which occurs by dynamic impact 2 Sizing which occurs by attrition and shear in the second zone where small clearance exists between the hammer and the screen bar producing a particle range of 15 50 µm The material is crushed or shattered by the repeated hammer impacts collisions with the walls of the grinding