USS Pattern F436 Washer
What It Does
When a connection needs load spread over a wider area, a wide outside-diameter hardened washer provides more bearing surface than a standard circular washer. This USS pattern washer is used in structural bolting where added bearing area is required or specified, giving a hard bearing surface beneath the turned element that resists embedment into the connected steel. It is used with high-strength structural bolting assemblies where the larger diameter is appropriate, and meets ASTM F436.
The larger outside diameter spreads the clamping force across more of the connected material. This can be valuable when the connected steel is thinner or softer than the fastener, when the bolt bears near an edge or an opening, or when a project specification calls for a wider bearing footprint. By covering more surface area, the wide OD washer reduces bearing stress at the washer face compared with a standard circular washer of the same bolt size.
When to Use a USS Pattern Washer
A wide OD washer is appropriate where the connection benefits from more bearing area than a standard circular washer provides, or where the project documents specifically call for it. It is not a substitute for an extra-thick washer over an oversized or slotted hole; those two conditions call for different washers. Where the requirement is simply more bearing surface on a flat, standard-hole connection, the USS pattern is the right choice. When in doubt, the appropriate pattern should be confirmed against the connection design.
Finishes and Material Types
USS pattern F436 washers are available in plain finish and hot-dip galvanized. As with other F436 washers, Type 1 carbon or alloy steel is used for standard structural assemblies, and Type 3 weathering steel is used with weathering-steel assemblies. The washer finish and material type should match the bolt and nut used in the assembly.
Availability
Available in plain finish and hot-dip galvanized in common diameters. Larger and special sizes are manufactured to order.