A sems screw is a machine screw and free-spinning washer manufactured as one assembly. Steel SEMS are available with the following types of washers: internal tooth, external tooth, split-lock and conical. Stainless SEMS are offered with external tooth lock washers. Internal tooth SEMS are recommended when it is desirable to hide the teeth for appearance or to prevent snagging. External tooth SEMS are preferred over the internal tooth style as the teeth provide greater torsional resistance being on the larger radius. Split-Lock SEMS are preferred over tooth lock washer SEMS for use with hardened bearing surfaces. Conical SEMS provide a higher retained clamp load & improved compensation for thermal cycling and vibration and 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. SEMS screws are offered in different drive types for a number of different applications. These drive types include slotted, unslotted, Phillips, six-lobe, and combo (slotted and Phillips) with head styles like hex, hex washer, and pan for your commercial or industrial needs. BW Industrial Sales carries SEMS screws manufactured to meet the metric specifications of DIN 7985A, DIN 6902A, Modified DIN 127B, ISO 7045, JISB1187, JISB1188, in addition to standard ASME B18.13, SAE J82 specifications and recognized as the American National Standard. SEMS screw specifications vary from machine screws in that the maximum diameter of the unthreaded shank shall be less than the maximum major diameter of the thread by an amount sufficient to prevent disassembly of the washer from the screw. The unthreaded length on full threaded screws is measured to the contacting face of the washer instead of to the bearing face of the screw. The minimum under head fillet radius is equivalent to 5% of the basic screw diameter. BW Industrial Sales carries steel material finishes in clear zinc plated, black oxide, black zinc, yellow zinc, and RoHS zinc yellow. Steel screws are manufactured in AISI 1022 or equivalent steel with the steel washers using SAE 1055-1065 carbon steel for split-lock, SAE 1050-1065 carbon steel for the tooth-lock, and SAE 1050 carbon steel for the conical. Stainless screws are available in 18-8 (303 & 304 series) or 410 martensitic stainless steel. Stainless washers are offered in SAE J405 302-305 and 410 stainless. The screws for the SEMS assembly are manufactured to meet Rockwell hardness of B70 -B100. The steel and stainless-steel washers are designed to meet Rockwell hardness of C38-46, C40-50, C42-46, C35-43, and B88 minimum for stainless steel. Tensile strength for steel SEMS screws is a minimum of 60,000 psi and 96,000-99,000 psi for stainless steel SEMS screws. Available and ready-to-ship in a variety of sizes, styles and finishes. Browse our selection of sems screws for your building projects and industrial applications.
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contact our experienced and qualified BW Industrial Sales staff; or call us at
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