An external star washer is a metal ring with outward-pointing serrations that grip surfaces. It enhances grip, prevents loosening, and distributes load in fastened assemblies. Used in high-vibration applications, the "teeth" create tension, offering better stability than plain washers.

The washer’s outward-pointing teeth dig into the surface, creating friction and locking the fastener in place. This design resists loosening from vibrations or torque, ensuring the fastener stays secure. It’s ideal for dynamic environments like machinery and vehicles.

They are commonly made from stainless steel, carbon steel, or spring steel, often with zinc or phosphate coatings for corrosion resistance. Material choice depends on the application, with stainless steel preferred for high-strength and corrosion-resistant requirements.

Choose a washer based on the bolt/screw diameter and surface area requirements. Ensure the inner diameter matches the fastener and the outer diameter fits the contact surface. Correct sizing prevents damage, ensures effective grip, and distributes load appropriately.