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.
FAQs about Sealing and Cushioning Washers
It combines a metal backing with an elastomer lip that compresses under the fastener head to help block water, dust, and air leaks.
NBR is good for oils and fuels, EPDM for water and weather, and silicone for very hot or cold conditions and UV exposure.
Lightly used parts can sometimes be reused, but sealing performance is best with a fresh elastomer. Inspect for cuts or permanent set.
Tighten until the seal compresses uniformly without squeezing the elastomer out. Follow the fastener’s torque guidance when available.
Install with the elastomer against the mating surface and the metal backing toward the fastener head.
They can damp minor vibration and protect finishes. For heavy vibration, consider additional measures such as lock washers or threadlocking compounds.
They are designed to resist leaks at the fastener interface. Overall enclosure sealing also depends on surfaces, holes, and any additional gaskets.
Select the matching metric size such as M5, M6, or M8, verify inner diameter fit, and choose an outside diameter that fully covers the hole.
They can help isolate the joint, but material pairing still matters. Match metals when possible or use isolation practices.
Many finishes can be painted. Lightly clean and scuff the metal backing for adhesion and avoid solvents that attack the elastomer.