Aluminum Scrap Crusher The basic principle of scrap crusher is impact of material by hammer beating. When the material enters into the crusher, it is suffered impact from the high speed rotary hammers, flap of the crushing chamber body and at the same time strike among materials. Thus material is grinded by lots of times. The materials less than the sieving hole discharge from the clearance. Larger particles are hit again by the hammer. Final particle size is mainly decided by hole size of the sieve plate, so you can adjust the size by your requirements.