Slotted Pan Head Internal Tooth Machine Screw SEMS, Zinc Plated
Also known as:
Machine Screws with Lock Washers
SEMS are machine screws with free-turning captive lock washers—external tooth and internal tooth lock washers are common. The screw/washer assembly saves time when compared to using individual screws and washers. Internal SEMS, which have an internal tooth lock washer, are preferred when it is desirable to hide the teeth. The larger radius of an External SEMS, though, provides greater locking action. Length is measured from under the head.