ISO 9001 · IATF 16949 Stainless steel bonded seal

MOLDED SEALS

Bonded Seals (Dowty Washers)

A steel washer permanently bonded to a rubber sealing ring — self-centering under the bolt head for a reliable high-pressure seal on threaded ports, hydraulic fittings and flange joints. Metric and BSP sizes from existing tooling, custom sizes to order.

✓Self-centering design — the rubber ring seats itself under the fastener head
✓Zinc-plated steel with NBR as standard; stainless steel with FKM for corrosive service
✓Copper + NBR combinations for plumbing-style joints
✓Metric, BSP and imperial sizes
✓For hydraulic fittings, threaded ports, plugs and banjo bolts

TYPES

Metric · BSP · Self-centering

METAL

Zinc steel · Stainless

RUBBER

NBR · FKM

SERVICE

High-pressure ports

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TECHNICAL DATA

Material Combinations

Four standard combinations cover nearly every port-sealing job.

Combination	Use
Zinc-plated steel + NBR	General hydraulic ports and fittings
Zinc-plated steel + FKM	High-temperature oil circuits
Stainless steel + NBR	Outdoor and washdown environments
Stainless steel + FKM	Chemical processing and marine service

APPLICATIONS

Where It's Used

Everywhere a threaded port has to hold pressure.

HYDR

Hydraulic Fittings

Leak-free ports on manifolds, valves and cylinders.

PORT

Threaded Ports & Plugs

Sealing BSPP and metric ports under the plug head.

BANJ

Banjo Bolts

Fuel and oil line banjo connections.

PUMP

Pumps & Valves

High-pressure joints in fluid power equipment.

AGRI

Agricultural Machinery

Vibration-proof port sealing on field equipment.

OIL

Oil & Gas

Corrosion-resistant combinations for harsh sites.

COMMON QUESTIONS

Bonded Seal FAQ

How does a bonded seal work?

Tightening the fastener compresses the rubber ring trapped inside the metal washer, forming a high-pressure seal — while the washer prevents over-compression and extrusion.

Can bonded seals be reused?

We recommend replacing them at every disassembly — the rubber takes a compression set and will not seal as reliably a second time.

Which sizes are available?

Metric, BSP and imperial series from existing tooling. Send your thread size and we will match it.

Do you offer stainless steel versions?

Yes — stainless washers bonded with NBR or FKM for corrosive, marine and washdown environments.

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