A machine screw and free-spinning lock-washer manufactured as one assembly. Steel SEMS are available with the following types of washers: internal tooth, external tooth, split-lock and square-cone®. Stainless SEMS are offered with external tooth lock washers.
The washer/screw assembly makes this a locking screw with the washer providing the locking action. Machine pre-assembly provides cost savings to the end user. Internal Tooth SEMS: Recommended when it it desirable to hide the teeth for appearance or to prevent snagging. External Tooth SEMS: Preferred over the internal tooth style as the teeth provide greater torsional resistance being on the larger radius. Split-Lock SEMS: Preferred over tooth lockwasher SEMS for use with hardened bearing surfaces. Square-Cone® SEMS: Provides a higher retained clamp load & improved compensation for thermal cycling and vibration. Can accept a high tension load and maintain spring action. The washer design makes for better control during installation, and improved tool bit life. Ideal for clamping fragile materials and for spanning large clearance holes.