Flat Washers

Flat washers distribute a fastener's clamp load over a wider area, protecting the work surface from damage and preventing the bolt head or nut from pulling through. They are among the most-used fasteners in any assembly. We stock flat washers in SAE, USS, and fender patterns across every common material and finish.

SAE vs. USS vs. Fender

SAE flat washers have a smaller outside diameter and are sized to match the bolt — the standard choice for most machine and automotive work. USS flat washers have a larger OD and wider hole, suited to construction and rougher tolerances. Fender washers have a very large outside diameter relative to the hole, spreading load across thin or soft materials like sheet metal and wood.

Materials and Finishes

Steel with zinc plating: the economical standard for indoor and light outdoor use. Hot-dip galvanized for sustained outdoor exposure. 18-8 stainless for general corrosion resistance. 316 stainless for marine and chemical environments. Brass for electrical and decorative applications.

Dimensional Standards

Inch flat washers conform to ASME B18.22.1; structural washers to ASTM F436 (hardened) and ASTM F844 (USS/SAE). Metric flat washers follow DIN 125 / ISO 7089, with large-OD fender types per DIN 9021 / ISO 7093.

Selecting the Right Flat Washer

Match the washer's inside diameter to the bolt, and choose the OD pattern for your bearing needs — SAE for standard machine work, USS or fender for soft or oversized-hole applications. For structural joints, use hardened F436 washers rated to the bolt grade. Match the material and finish to the bolt to avoid galvanic corrosion — pair stainless washers with stainless fasteners.

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