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Custom Bonded Seal Dimensions, Materials, and Quotation Requirements
Quick Answer: A custom bonded seal is a metal washer with a molded rubber sealing lip, made to your required thread size, outside diameter, metal material, rubber material, and operating conditions. CORASEALS supplies custom bonded seals for bolt heads, drain plugs, filler plugs, and non-standard sealing points. Send us your thread size, ID, OD, washer thickness, metal material, rubber material, fluid, pressure, temperature, and quantity for a quotation.
What Is a Custom Bonded Seal
A bonded seal has a metal outer ring and a rubber sealing element. The metal ring limits compression. The rubber lip seals against the seating face. Custom bonded seals are produced when a standard size is not available, or when the application requires a different metal grade, rubber compound, thickness, or outside diameter.
Dowty seal is a common trade name for this type of seal. CORASEALS uses the descriptive term bonded seal and treats Dowty as a third-party trade name.
How to Specify Custom Bonded Seal Dimensions
Start with the thread size or bolt diameter. Measure the housing bore, seat diameter, and available outside diameter. Include the washer thickness and the rubber inside diameter if the hole must fit a specific bolt or plug. If the seat has a counterbore, include that diameter and depth.
Standard bonded seals are often referenced to DIN 7603. A custom bonded seal can use the same sealing principle with dimensions changed to match your housing and thread.
State dimensions in metric or inch units. Do not mix units. For example, a typical inquiry may state thread size M14, OD 20 mm, washer thickness 1.5 mm, and NBR rubber.
Material Selection for Custom Bonded Seals
Common metal ring materials include carbon steel, 304 stainless steel, and 316 stainless steel. Common rubber materials include NBR, FKM, and EPDM. NBR is widely used for mineral oil and hydraulic oil. FKM is selected for higher temperature and chemical resistance. EPDM is used for water, steam, and brake fluid. The final material combination must match the fluid, temperature, pressure, and seat surface.
| Material Type | Common Grade | Common Use |
|---|---|---|
| Metal ring | Carbon steel | General hydraulic and lubrication systems |
| Metal ring | 304 stainless steel | Water, corrosion resistance, and general chemical exposure |
| Metal ring | 316 stainless steel | Seawater, chemical, and acid environments |
| Rubber | NBR | Mineral oil, hydraulic oil, and fuel |
| Rubber | FKM | Higher temperature and aggressive fluids |
| Rubber | EPDM | Water, steam, brake fluid, and weather |
Most bonded seals use rubber in the 70 to 90 Shore A range. The correct hardness depends on the seating face condition, pressure, and required compression.
Application Limits to Check Before Ordering
Bonded seals work best in static threaded joints with a flat seat. The rubber lip must be compressed by the metal ring without being cut or extruded. Check the seat surface finish, bolt torque, thread clearance, and counterbore depth. A damaged seat or incorrect outside diameter can cause leakage.
Custom Bonded Seal Quotation Requirements
To receive a quotation, send us the following information:
- Thread size or bolt diameter
- Housing bore or seat diameter
- Required OD and washer thickness
- Rubber ID and lip profile
- Metal ring material
- Rubber material and Shore A hardness
- Fluid, pressure, temperature, and seat surface finish
- Required quantity and any drawing, photo, or sample
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