Standard SAE Flat Washer Size

Standards

• Flat washers are typically manufactured to specifications established by national or international standards organizations. Flat washers that conform to standards established by the American National Standards Institute are referred to as meeting ANSI standards. Flat washers that conform to standards established by the Society of Automotive Engineers are referred to as meeting SAE standards. SAE flat washers are lighter and smaller than comparable ANSI flat washers. They are intended to be used with fine-thread bolts and nuts. SAE flat washers are designated Type A Plain Washers, narrow series.

Inside Diameter

• The size of an SAE flat washer may be referred to either as a number or by a division of an inch. An SAE flat washer's inside diameter is slightly larger than the bolt it is intended to fit over. The inside diameter for a #6 SAE flat washer is 5/32 inch, the inside diameter of a 1/2-inch SAE flat washer is 17/32 inch, and the inside diameter of a 7/8-inch SAE flat washer is 15/16 inch.

Outside Diameter

• The outside diameter of an SAE flat washer is slightly larger than the nut that is intended to match with the corresponding bolt. The outside diameter of a #6 SAE flat washer is 3/8 inch, the outside diameter of a 1/2-inch SAE flat washer is 1-1/16 inch, and the outside diameter of a 7/8-inch SAE flat washer is 1-3/4 inch.

Thickness

• The thickness of an SAE flat washer is determined by its size. SAE flat washers #6, #8 and #10 are all 3/64 inch thick; 1/2-, 9/16- and 5/8-inch SAE flat washers are 3/32 inch thick; and 3/4-, 7/8- and 1-inch SAE flat washers are all 9/64 inch thick.