Washers may be simple, but they make fasteners perform better. A washer is a thin, flat, circular part with a centrally located hole used between the bearing surface of the fastener and the part being attached to improve stress distribution, protect surfaces, and maintain clamp load. Below is a practical guide—plus a quick look at what Allied Bolt & Screw stocks.
Why Washers Matter
- Distribute load: Prevents embedding, pull-through, and surface marring.
- Maintain preload: Helps combat relaxation and vibration loosening.
- Corrosion & environment: Coatings and materials match the jobsite and service life.
- Tolerance & fit: SAE vs. USS sizing ensures the right ID/OD for your hardware.
SAE vs. USS: What’s the Difference?
SAE (Society of Automotive Engineers) flat washers typically have a smaller ID and OD to fit closer tolerances—great for machine work and harder materials. USS (United States Standard) flat washers have a larger ID and OD, offering broader load spread—ideal for construction and structural applications.
Common Materials & Finishes
- Zinc plated: General indoor corrosion protection.
- Zinc yellow (Grade 8): Distinct yellow chromate, pairs with high-strength fasteners.
- Hot-dip galvanized: Thick, rugged coating for outdoor and marine environments.
- Plain steel: Economic, for dry indoor or painted assemblies.
- Nickel plated / black oxide: Aesthetic finishes; nickel resists tarnish, black oxide reduces glare.
- Non-metallic (nylon, neoprene): Electrical isolation, sealing, cushioning, and vibration damping.
What We Carry
- Flat Washers — SAE, Zinc Plated
- Flat Washers — USS, Zinc Plated
- Flat Washers — SAE, Grade 8, Zinc Yellow Plated
- Flat Washers — USS, Grade 8, Zinc Yellow Plated
- Extra Thick Flat Washers — SAE, Grade 8, Zinc Yellow Plated
- Extra Thick Flat Washers — USS, Grade 8, Zinc Yellow Plated
- F436 Structural Flat Washers — Plain Steel (Including Domestic)
- F436 Structural Flat Washers — Hot Galvanized (Including Domestic)
- Flat Washers — Hot Galvanized
- Dock Washers — Hot Galvanized
- Square Washers — Hot Galvanized
- Horseshoe Shims — Hot Galvanized
- Ogee Washers
- Bevel Washers — Galvanized
- Bevel Washers — Plain Steel
- Finishing Washers — Nickel Plated
- Finishing Washers — Black Oxide
- Split Lock Washers — Zinc Plated
- Split Lock Washers — Grade 8, Zinc Yellow
- Split Lock Washers — Hot Galvanized
- Internal and External Tooth Lock Washers — Zinc Plated
- Bonded Neoprene Washers
- Neoprene (Rubber) Washers
- Flat Washers — Nylon
- Fender Washers — Nylon
- Fender Washers — Zinc Plated
Specialty & Structural Types—Where They Shine
- F436 Structural: Designed for structural bolting (A325/A490 equivalents). Use with structural steel connections where hardness and flatness matter.
- Dock & Square: Extra large bearing surfaces for timber, ledger, and heavy framing.
- Ogee: Thick, contoured profile for masonry and restoration work.
- Bevel: Corrects for sloped flanges or angled surfaces (e.g., I-beam flanges) to keep nut faces parallel.
- Finishing: Cup-style washers that present a clean, finished look with countersunk or oval head screws.
- Split/Tooth Lock: Provide frictional resistance to loosening in dynamic assemblies—choose split for general use, toothed for bite under the head.
- Non-metallic & Bonded: Nylon for insulation and weight savings; neoprene and bonded styles for sealing roofing panels, enclosures, and vibration damping.
Selection Checklist
- Match the standard: SAE for tight fits; USS for broader load spread.
- Match the grade: Pair Grade 8 washers with Grade 8 bolts; use F436 for structural assemblies.
- Match the environment: Choose hot-dip galvanized for harsh outdoor use; zinc for general indoor; nickel/black oxide for appearance.
- Consider geometry: Need more bearing area? Use fender, dock, or square washers. Need alignment? Use bevel washers.
- Control vibration & sealing: Use lock, neoprene, or bonded washers where appropriate.
Need Help Spec’ing Washers?
Bring us your drawings, specs, or a sample. Allied Bolt & Screw can help you select the correct standard, grade, finish, and size—so your assemblies go together right the first time and stay tight.
