Description: 

USS and SAE (Type A) are the most widely used types of washers. SAE standard washers generally have a smaller ID and OD than USS standard washers. Commonly used with bolts, screws, and nuts.

Material:

• Low Carbon Steel
• Hardened Steel
• Stainless Steel
• Nylon
• Brass
• Aluminum

Grades:

Flat washers do not have a specific grade as traditional fasteners such as Grade 5 or Grade 8 bolts do however there are two common types of steel used.

• Standard steel flat washers (low carbon steel) are not rated for hardness.
• Hardened steel flat washers.

Markings:

• Standard steel flat washers generally do not have any markings.
• Hardened steel flat washers usually have a vendor identification but do not follow any traditional grade marking rule.

Plating:

• Plain
• Zinc
• Hot Dip Galvanized

How to measure:

Note that the inside diameter(ID) is typically 1/16” bigger than the bolt size that they fit for sizes 1” and smaller.  For sizes 1 1/8” and larger the ID  is 1/8” bigger than the bolt size that they fit. IE, a 1/2” washer has a 9/16” ID and a 1 1/8 washer has a 1 1/4” ID.

Application:

Flat washers are used primarily to distribute the load of a fastener across a larger area than just the head of the fastener.

Abbreviation / Jargon:

• Cut Washer
• Flats

Part Number Prefix:

• 0FW* (Steel)
• 1FW* (Stainless Steel)
• 2FW* (Brass)
• 3FW* (Aluminum)
• 4FW* (Nylon)

Style / Types:

• USS Flat Washers
• USS Hardened Flat Washers
• SAE Flat Washers
• SAE Hardened Flat Washers
• Square Washers
• Finish Washers
• Brass Flat Washers
• Aluminum Flat Washers
• Nylon Washers
• Special Flat Washers

Their are many more types of washers. Some do not fall under the FW prefix. We will go over them later.