Flat Washers – Best 316 Stainless Steel SAE, Standard Washers, Box of 1000

Description

Flat washers are the small part that makes every bolted joint stronger, cleaner, and longer lasting. A washer sits between the nut or bolt head and the surface you’re fastening, spreading clamping pressure over a wider area so the hardware seats firmly without digging into the material. Our stainless steel flat washers are made from 316 stainless steel, a marine-grade alloy built to resist rust and corrosion outdoors. They come in two styles, SAE washers and standard flat washers, in 1/4″, 5/16″, and 3/8″ sizes, and every size ships in a bulk box of 1000.

Why 316 Stainless Steel

316 stainless steel is a marine-grade alloy with excellent resistance to rust and corrosion, the same type of steel used on boats, docks, and coastal hardware. Outdoor furniture, decks, and structures face rain, humidity, snow, pool water, and salt air all year long. Plain steel or zinc-plated washers can rust, leave stains on the surrounding material, and lock up the joint over time. 316 stainless steel flat washers stay clean, keep their finish, and let you tighten or take apart hardware easily years down the road.

Matching your washers to your bolts matters too. Pairing 316 stainless washers with 316 stainless bolts keeps the whole joint the same material, so you avoid mixing metals that can corrode each other outdoors.

SAE Washers vs. Standard Flat Washers

We carry both styles so you can pick the right fit for the job:

• SAE washers – A closer fit around the bolt with a smaller outside diameter. SAE washers give a neat, compact look and work well where space is tight or where the washer will be visible on finished furniture.
• Standard flat washers – A wider outside diameter that covers more surface area. Standard flat washers are a great choice for softer materials like wood and poly lumber, where a broader bearing surface helps the nut seat without pressing into the material.

Sizes and Dimensions

Choose the washer size that matches your bolt diameter:

• SAE 1/4″ – 0.281″ ID x 0.625″ OD
• SAE 5/16″ – 0.33″ ID x 0.607″ OD
• SAE 3/8″ – 0.406″ ID x 0.812″ OD
• Standard 1/4″ – 0.30″ ID x 0.675″ OD
• Standard 5/16″ – 0.343″ ID x 0.750″ OD
• Standard 3/8″ – 0.390″ ID x 1.00″ OD

Every size is sold in a bulk box of 1000 pieces, which gives furniture builders, repair shops, contractors, and dealers a steady supply at a low cost per washer.

Perfect for Poly Furniture and Outdoor Projects

Our flat washers are a natural match for poly furniture, including Adirondack chairs, rockers, gliders, porch swings, benches, and picnic tables. They’re also ideal for decks, docks, fences, gates, playsets, and garden structures. Pair them with our 316 stainless steel carriage bolts and wafer head bolts for a complete, rust-resistant fastening system built for the outdoors.

Why Use a Washer

• Protects the surface – Keeps the nut from grinding into wood or poly lumber as you tighten.
• Spreads pressure – Distributes clamping force over a wider area for a firmer, more even joint.
• Helps joints stay tight – A flat, even bearing surface helps hardware hold its position over time.
• Covers oversized holes – Bridges slightly large or worn holes so the nut still seats properly.

Easy Installation

Slide the washer onto the bolt before threading on the nut, so the washer sits flat between the nut and the material. Tighten until snug. In poly lumber, avoid over-tightening, which can compress or distort the material. Recheck your hardware after the first few uses and tighten as needed.

Simple Care Tips

• Inspect outdoor hardware at the start of each season
• Retighten any nuts that have loosened
• Rinse away dirt and debris, especially near pools or the coast
• Keep a supply of flat washers on hand for quick repairs

Built to Last Outdoors

Finish every joint the right way. Our 316 stainless steel flat washers are rust-resistant, available in SAE and standard styles, and packed in bulk boxes of 1000. They’re the essential hardware for poly furniture and outdoor builds that live outside year-round.