120 Piece Thru-hardened USS Extra Thick Flat Washer Assortment Starter Kit

When a standard flat washer pulls through soft steel plate, a worn flange face, or a composite mounting surface, the problem is bearing surface — not the bolt. This 120-piece USS extra thick flat washer assortment covers six diameters (1/4" through 5/8") in thru-hardened extra thick stock, organized across a labeled 6-hole plastic drawer so the right size is always within reach. What's Included Thru-hardened USS extra thick flat washers — 1/4", 5/16", 3/8", 7/16", 1/2", and 5/8" diameters Multiple pieces per size 120 pieces total 6-hole small plastic drawer — pre-labeled, one compartment per diameter Specifications Standard USS (United States Standard) — larger OD than SAE for the same bolt diameter Type Extra thick — up to 50% thicker than standard flat washers Hardening Thru-hardened (full cross section, not surface only) Diameters 1/4", 5/16", 3/8", 7/16", 1/2", 5/8" Total pieces 120 Storage 6-hole small plastic drawer SKU ASST6FWCXT Best For Heavy machinery and structural bolting — USS OD distributes clamping load over more surface area than SAE, reducing risk of pull-through Soft or thin base materials — composite panels, thin sheet metal, worn flange faces, and soft steel where standard washers embed under torque In-plant and industrial maintenance — anywhere repeated loading cycles cause standard flat washers to compress or deform over time Construction and fabrication — high-load structural connections where bearing surface is as important as fastener strength Fleet and equipment repair — a ready organized stock of the six most common heavy-duty washer diameters About Thru-Hardened USS Extra Thick Washers USS flat washers use a larger outside diameter than SAE flat washers for the same bolt size, which distributes clamping force over a wider area. In extra thick form, they resist deformation under high torque — a standard washer can embed into softer material or compress over time, gradually reducing clamp load. Thru-hardening means the full cross section is hardened, not just the surface, so they hold their shape under repeated loading cycles. USS dimensions are the common choice for general construction, machinery, and heavy industrial fastening where bearing surface matters. If your application requires tighter OD clearances — precision clearance holes, close-tolerance flanges, or anywhere the USS OD would interfere with adjacent hardware — see our SAE Extra Thick Flat Washer Assortment for the same 1/4" through 5/8" range in SAE dimensions. Shipping & Ordering Ships within 1–2 business days from our warehouse Volume pricing available — save up to 20% when ordering 3 or more kits B2B accounts: Fleet managers, facilities teams, and machine shops can apply for a business account with custom pricing and a dedicated rep — contact us to get started