When evaluating a stainless hammer mill, you must prioritize the material grade, typically SUS304 or SUS316L, to ensure corrosion resistance and food/pharmaceutical safety. Key performance metrics include the rotor speed (RPM), which dictates fineness, and the screen mesh size, which determines the final particle distribution. Ensure the motor is copper-core with an IP55 rating or higher for durability, and check if the unit features a water-cooling system to prevent heat-sensitive materials from degrading during high-speed friction.