USS flat washers

USS flat washers (United States Standard flat washers) are plain, flat, circular metal discs with a central hole, designed to be placed under a bolt head or nut to:

Distribute load – Prevent fastener pressure from damaging soft surfaces.

Provide spacing – Adjust alignment or gap between components.

Reduce friction – Help nuts rotate smoothly during tightening.

Protect surfaces – Act as a buffer against abrasion or galvanic corrosion.

They are thicker and larger in diameter than SAE flat washers, making them suitable for heavier-duty applications in construction, machinery, and structural steelwor

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Standard

ASTM F844 – Standard Specification for Washers, Steel, Plain (Flat), Unhardened for General Use.
Governing Standards:
ANSI B18.22.1 (Dimensional Standard)
SAE J480 (For SAE flat washers, which are thinner than USS)
ASTM F436 (For hardened washers, used with structural bolts)

Applications (Uses)

Load Distribution – Prevents bolt/nut heads from digging into soft materials.
Spacing & Alignment – Adjusts fastener positioning.
Electrical Insulation – When non-metallic washers are used.
Common Industries: Construction, automotive, machinery, structural steel, and general manufacturing.

Common Materials

USS flat washers are manufactured from various materials depending on application requirements:

Carbon Steel (Most Common)
Grade A (Low Carbon Steel, Unhardened) – General-purpose use, cost-effective.
Grade C (Medium Carbon Steel) – Slightly stronger than Grade A.
ASTM F844 Compliance – Typically covers unhardened carbon steel washers.

Stainless Steel (Corrosion-Resistant)
Grade 304 (18-8 Stainless Steel) – Good corrosion resistance, general use.
Grade 316 (Marine-Grade Stainless) – Superior corrosion resistance for harsh environments (saltwater, chemicals).

Alloy Steel (High-Strength Applications)
Sometimes used in hardened washers (ASTM F436), but USS washers under ASTM F844 are usually unhardened.

Non-Ferrous Metals (Special Applications)
Brass – Electrical conductivity, corrosion resistance.
Aluminum – Lightweight, corrosion-resistant (avoids galvanic corrosion with steel).

Dimensions & Size Range

USS Washers vs. SAE Washers:
USS washers are thicker and have a larger outer diameter (OD) than SAE washers.
Example: A ½" USS washer is thicker than a ½" SAE washer.

Size Range:
Nominal Bolt Sizes: #4 (0.112" ID) up to 1½" (1.5" ID)
Common Dimensions (per ANSI B18.22.1):

Bolt Size	Inside Diameter (ID)	Outside Diameter (OD)	Thickness
#4	0.125" (3.2 mm)	0.312" (7.9 mm)	0.026" (0.66 mm)
¼"	0.281" (7.1 mm)	0.625" (15.9 mm)	0.049" (1.24 mm)
½"	0.562" (14.3 mm)	1.125" (28.6 mm)	0.084" (2.13 mm)
1"	1.062" (27 mm)	2.000" (50.8 mm)	0.134" (3.4 mm)
1½"	1.562" (39.7 mm)	3.000" (76.2 mm)	0.165" (4.2 mm)

Comparison with Other Washer Types

Feature	USS Flat Washer	SAE Flat Washer	Hardened Washer (ASTM F436)
Thickness	Thicker	Thinner	Varies (hardened)
OD	Larger	Smaller	Similar to USS
Material	Soft steel, SS	Soft steel, SS	Hardened steel
Standard	ASTM F844 / ANSI B18.22.1	SAE J480	ASTM F436

Product Parameters

Product Name	USS flat washers
Material	carbon steel,alloy steel,stainless steel,brass,Titanium
Size	Imperial Sizes: #4 (0.112" ID) up to 1½"(1.5" ID)
Surface	Plain, black,zinc plated,zinc yellow plated,Hot Dip Galvanized,passivated,Mechanical Galvanzied,Phosphate Coating
Production Process	Stamping
MOQ	800KG
Package	Carton & Pallet