Sems Screw

A sems screw is a screw with a pre-assembled washer, often a captive spring or flat washer. It saves handling time during assembly.

A sems screw carries a captive washer under its head so the washer stays on during assembly. It often drives into a tapped hole or nut with a screwdriver or nut runner. A hole of matching thread suits it.

Sems screws are usually made of steel or stainless steel. The washer can be of a similar material or a different one. Plated steel is common for general assembly.

This is a general guide to checking this kind of part. It says nothing about any supplier's parts.

Ask for a certificate of conformance and a material test certificate. Check the washer retention, the thread and the finish on receipt.