Sealing & Cushioning Washers
What are Sealing and Cushioning Washers?
Sealing and cushioning washers are assemblies that combine a metal backing with an elastomer layer to create a compressible seal under a screw or bolt head. They reduce vibration, protect finished surfaces, and help block water, dust, and air leaks in light to moderate duty assemblies.
What do bonded sealing washers do?
Bonded sealing washers use a metal ring for support and a molded elastomer lip that compresses during tightening. The compression forms a barrier at the fastener head and around the shank to help prevent leaks and isolate vibration.
When should I use sealing or cushioning washers?
- Roofing, siding, HVAC panels, and sheet metal where weather resistance matters
- Electrical and electronic enclosures that need dust or splash protection
- Appliances, pumps, and light machinery to reduce buzz and rattle
- Soft or coated surfaces that need a protective cushion under the fastener head
Types of sealing and cushioning washers
- Bonded sealing metal backed with an elastomer lip for leak resistance
- Cushioning compressible washers that focus on vibration control and surface protection
Materials and elastomers
Stainless steel 304 and 316
Corrosion resistant metal backing for outdoor and marine environments. Choose 316 near salt or harsh chemicals.
Aluminum
Lightweight backing for general exterior panels and where galvanic compatibility with aluminum is preferred.
NBR nitrile
Common elastomer for oils and fuels at moderate temperatures.
EPDM
Strong choice for water exposure, steam, and outdoor weathering.
Silicone
Wide temperature range and good UV resistance for hot or cold conditions.
How to size sealing and cushioning washers (inch and metric)
- Match the nominal size to your fastener size such as 1/4 in or M6
- Confirm the inner diameter fits the shank without cutting the elastomer
- Select an outside diameter that covers the hole and lands fully on the surface
- Choose the backing thickness and elastomer hardness to suit clamp load and vibration needs
Installation tips for a reliable seal
- Place the washer under the head with the elastomer side facing the surface
- Tighten gradually until the seal compresses evenly and stop before over squeezing
- Use clean, flat bearing surfaces and avoid burrs that could nick the seal
- Recheck fasteners after thermal cycling or initial run in
Sealing washers vs alternatives what to know
Sealing washers offer a fast, hardware level seal with simple assembly. For higher pressure or large joint gaps, consider gaskets, O rings, or sealants in addition to proper fasteners.