Finishing Washer

Finishing washers, also referred to as cup washers or countersunk finishing washers, are specially formed washers with a concave (cup-shaped) profile designed to cradle flat or oval head screws. They provide a large bearing surface while creating a neat, finished appearance without requiring a countersunk recess in the mating surface.

Applicable Standards
Note: Currently, there is no single set of requirements universally accepted as the industry standard for countersunk finishing washers. The following dimensions serve as general guidelines:

#4 to #12 screw sizes (metric equivalents available)
1/4″ to 3/8″ and larger fractional sizes
Custom dimensions available upon request

Materials

Steel: Carbon steel (hot-rolled, cold-rolled, or machined from bar stock)
Stainless Steel: 18-8 (304) for general corrosion resistance; 316 for marine/harsh environments
Brass: Warm decorative finish for architectural and furniture applications
Silicon Bronze: Marine-grade with excellent corrosion resistance
Other alloys available upon request

Surface Treatments

Steel: Zinc plating (clear or yellow), nickel plating, black oxide, plain/oiled finish
Stainless Steel: Generally supplied without additional finish (plain/passivated)
Brass: Nickel plating, plain polished, or custom finishes

Size Selection
Washer size refers to its nominal hole size and is based on the screw size (e.g., #6, #8, #10, 1/4″). The outside diameter (OD) is always larger. Choose by screw size and confirm the screw head nests properly in the cup without wobble.

Common Applications