What are SEMS?
Pre-Assembled Washers and Screws (SEMS) Save Time and Reduce Costs
Washers are commonly used in conjunction with a bolt, nut or screw to reduce the under-head bearing pressure when fastening mating components.
In manufacturing where assembly time accounts for a massive proportion of the overall product cost, any reduction of component assembly time can lead to large cost savings. If the washers and screws are combined, or pre-assembled together when the fasteners are first manufactured, some of the assembly cost can be transferred to the fastener supplier and taken out of the overall cost of production.
By using washers with a slightly smaller internal diameter and assembling it with the screw before thread rolling, the washer remains assembled and free to rotate as a pre-assembled screw and washer unit, commonly known as a SEMS screw. This additional process will increases the cost of the fastener but will generate an overall cost saving for production.