1/4-20X3/8 Unslotted Hex Washer External Sems Machine Screw Fully Threaded Zinc And (Pack Qty 3 000) BC-1406EW

PICTURES ARE REPRESENTATIVE OF ITEM BUT ARE NOT OF THE ACTUAL ITEM. Product dimensions finish head markings thread length stamping shape or forging shape etc. may differ from picture. Products are guaranteed to meet the specifications to which they are manufactured. Specifications allow for tolerances in dimension and shape which can vary from lot to lot. A machine screw and free-spinning lock-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.. The washer/screw assembly makes this a locking screw with the washer providing the locking action. Machine pre-assembly provides cost savings to the end user. Internal Tooth SEMS: Recommended when it it desirable to hide the teeth for appearance or to prevent snagging. External Tooth SEMS: Preferred over the internal tooth style as the teeth provide greater torsional resistance being on the larger radius.. Split-Lock SEMS: Preferred over tooth lockwasher SEMS for use with hardened bearing surfaces. Conical SEMS: Provides a higher retained clamp load & improved compensation for thermal cycling and vibration. 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.. Steel Screws-- AISI 1022 or equivalent steel. -- Steel Washers-- Split-lock: SAE 1055-1065 carbon steel; Tooth-lock: SAE 1050-1065; Conical: SAE 1050.. Stainless Screws-- SAE 18-8 stainless steel or 410 martensitic stainless steel -- Stainless Washers-- Split-lock: SAE J405 302-305; Tooth-lock: SAE 410 stainless steel; Conical: 410 stainless steel..