Externally threaded screws and bolts with captive washers
SEMS screws provide design and manufacturing efficiencies by combining multiple parts, captive washer and screw, into one versatile fastener. This design reduces two part numbers to one and also saves assembly time on the production floor. The assembly allows you to increase bearing surface over a traditional cold headed part. One part to inventory, track and assemble.
It was a great leap forward when screws and washers became pre-assembled into the SEMS screw. This screw includes a free-spinning washer that is locked into place because the screw thread (created after the washer is put on) is larger than the hole of the washer. SEMS are low cost, easy to use and are available from our company in many different sizes, styles, head types, drives, materials and other choices, depending upon your application needs.
It is not uncommon to design and manufacture double-washer SEMS screws, a fastener with two free-spinning washers. These are more cost-effective than conical washers or other alternative designs, exhibit good holding strength, and are now ubiquitous in electrical and electronic applications.