Rivet Washers

When do I need a backup washer?

Any time the blind side material cannot support the formed rivet head on its own. That covers three common situations. Soft materials like plastic, fiberglass, wood, and composite crush under the concentrated pressure of a forming rivet, so the joint goes loose almost immediately. Thin sheet metal deforms and dimples around the rivet rather than clamping flat. Oversized or worn holes leave the rivet body with too little material to grip, which is constant in repair work. In all three cases a washer converts a small, concentrated contact patch into a broad one, and the joint holds. The one thing to remember is that the washer becomes part of your material stack, so its thickness counts toward the rivet's grip range.

Why use rivet washers

• Prevents pull-through in plastic, fiberglass, wood, and thin sheet
• Spreads clamping load across a much wider area on the blind side
• Covers oversized, elongated, or worn holes in repair work
• Gives the rivet a hard surface to form against instead of soft material
• Increases pull-out resistance without moving to a larger rivet diameter

Materials and sizes stocked

• 304 stainless steel, for outdoor, marine, and washdown joints, 0.058 inch thick
• Aluminum, for aluminum panels and lightweight assemblies, 0.062 inch thick
• Zinc plated steel, economical for general indoor and light exterior work, 0.062 inch thick
• Sizes covering 1/8, 5/32, 3/16, and 1/4 inch rivet diameters
• Outer diameters run from 0.375 inch on the 1/8 up to 0.562 inch on the 1/4

Common applications

• Riveting into fiberglass, plastic, and composite panels
• Thin gauge sheet metal where the rivet would dimple the material
• Trailer, truck body, and RV panel repair over worn holes
• Boat and marine work, using stainless washers with stainless rivets
• Wood, laminate, and soft substrate joints
• Any repair where the original hole has enlarged

Match the washer material to the rivet wherever you can, so pair stainless washers with our closed end rivets in marine work. If you would rather solve the problem from the head side, large flange rivets spread load there, and tri-fold rivets spread it on the blind side without a separate part.

Related Categories

• Blind Rivets
• Large Flange Rivets
• Tri-Fold Rivets
• Rivet Tools
• Rivet Products

Rivet Washer FAQs

What size rivet washer do I need?

Match the washer to the rivet diameter, not to a bolt size. A 3/16 inch rivet takes a 3/16 inch rivet washer, whose inner diameter is sized to slip over the rivet body with minimal clearance. Using a standard flat washer with a loose hole lets the rivet body form unevenly.

Does the washer count toward grip range?

Yes, always. Add the washer thickness to your total material stack when selecting the rivet. Forgetting this is one of the most common ways people end up outside the grip range, since the washer can add over a sixteenth of an inch to the calculation.

Which side does the washer go on?

The blind side, behind the material, so the rivet body forms against it. Slide the rivet through the workpiece, put the washer over the protruding body on the far side, then set the rivet. On a truly blind joint this means you need at least enough access to place the washer before setting.

Can I use a regular flat washer instead?

It is not ideal. Rivet washers have inner diameters matched to rivet body sizes and a thickness chosen to work within typical grip ranges. A standard flat washer usually has a looser hole and different proportions, which lets the rivet form unevenly and reduces the holding benefit.

Should the washer match the rivet material?

Wherever the joint may get wet, yes. A steel washer against an aluminum rivet in a damp environment sets up galvanic corrosion at exactly the point you were trying to reinforce. Stainless washer with stainless rivet, aluminum with aluminum.

Do I need washers on both sides?

Usually only the blind side, since that is where the rivet forms and where pressure concentrates. If the head side material is equally soft, use a large flange rivet rather than adding a second washer, since a washer under the head can shift during setting.