Pan head SEMS machine screw is pre-assembled together with flat washer and spring lock washer as one piece. It adopts machine thread, designed to match nuts.

Flat washer evenly distributes compression load to protect workpiece surface; spring washer provides elasticity for auxiliary anti-loosening. Materials: Grade 4.8 carbon steel, 304 / 316 stainless steel optional. Surface finish: blue-white zinc, yellow zinc, black oxide, passivated for stainless steel. Widely applied in sheet metal, electrical cabinets and hardware assembly, simplifying installation and avoiding missing washers.