Combination screws (SEMS screws) are fasteners with a washer (flat washer, spring washer, or a combination) pre‑assembled onto the screw. The washer rotates freely on the thread but cannot fall off, simplifying the installation process, improving productivity, and eliminating the risk of missing washers. Common head types include cross‑recessed pan head, hexagon socket head, Torx® head, etc. These screws are ideal for applications requiring anti‑loosening, increased bearing surface, or protection of the workpiece surface from scratching.
Customizable options:

Materials: Carbon steel (e.g., C1008/C1022), alloy steel (e.g., SCM435/10B21), stainless steel (SS304/SS316), brass, etc.

Surface finishes: Electroplated zinc (blue/white, yellow, black), hot‑dip galvanizing, Dacromet, nickel plating, chrome plating, black oxide, phosphating, eco‑friendly zinc‑aluminum coating, etc.

Washer types: Flat washer, spring washer, conical washer, internal/external tooth lock washer, combined washer (flat + spring), etc.

Other variables: Nominal diameter (M2–M12), length (4mm–80mm), head type, drive type, washer material and hardness can be manufactured to customer drawings.
Widely used in electronic products, home appliances, automotive parts, instruments, and furniture assembly.