This specialised SEMS screw features an external teeth lock washer (serrated washer) pre‑assembled under a cross recessed pan head, conforming to DIN6907. The radial teeth on the washer bite into both the screw head underside and the workpiece surface, creating a positive mechanical lock that resists loosening under severe vibration. Unlike ordinary spring washers, the external teeth provide a strong anti‑rotation effect without damaging the screw head finish. The screw body can be carbon steel or stainless steel, with zinc plating or plain finish as required. This design is ideal for applications where chemical threadlockers are not allowed.

• Agricultural machinery: harvesters, tillers – high vibration environments.

• Industrial washing machines and centrifuges: door hinges and covers.

• Generator sets and air compressors: base mounting screws.

• Rail vehicle interior fittings: seats, luggage racks.

• Construction machinery: tower crane platform connections.

• Positive mechanical locking – teeth embed into the workpiece, far better than friction‑based spring washers.

• No extra parts – one component combines screw and lock washer.

• Reusable (limited cycles) – retains some anti‑loosening ability after disassembly.

• Minimal surface marking compared to internal teeth washers.

• DIN6907 standard ensures reliable dimensions and performance.