Metallics JWW82SS Washers 3/8 USS Flat SS (Jar 100)

Stainless steel throughout, material and finish both, so there is no plating to wear through. That makes them suitable for exterior mounting, wet mechanical and pump rooms, and pool or coastal work where a zinc-plated washer would bleed rust onto the surface it is clamped to.

USS washers like the JWW82SS have a larger outside diameter and a wider bearing surface than SAE washers of the same bolt size, which spreads clamp load over more material. That is what you want on sheet metal, strut, wood, or any soft or oversized hole. SAE is the narrower pattern, used where clearance around the fastener is tight or the washer has to sit inside a counterbore or channel.

Better not to as a habit. The JWW82SS is solid stainless, and pairing stainless hardware against zinc or galvanized steel in a wet location puts the zinc on the losing end of a galvanic couple, so the plated bolt corrodes first. For exterior or damp work, keep the bolt, nut and washer all stainless. Indoors and dry, the mix is not a practical problem.

Thickness runs 0.064 to 0.104 inches, which is the standard USS range for this bolt size. That stack-up matters when you are threading into a shallow channel nut or have limited bolt projection: count roughly a tenth of an inch per washer when you figure thread engagement.

The JWW82SS is built to the ANSI dimensional pattern for a 3/8 USS flat washer, with the 0.433 to 0.453 inch bore and 0.064 to 0.104 inch thickness that pattern calls for. So it interchanges with any other ANSI 3/8 USS flat washer already on the job.

Each jar holds 100 washers. The jar pack is the reason these end up on service trucks instead of in a bin: it keeps one size separated and pours without spilling the whole count. Jar weight is 0.62 lbs.

Load spreading. A USS flat washer puts the clamp force onto a wider footprint so the bolt head does not dig into or deform the material underneath, and it bridges an oversized or slotted hole. On strut, channel, sheet metal enclosures and wood blocking, that is the difference between a joint that stays tight and one that crushes and loosens.