Self-Seal® O-Ring Type

Positive Sealing–Pressure and Vacuum
Cold-Formed for Superior Strength and Uniformity
High Re-Usability
Optional Self-Locking Capability

Self-Seal® fasteners, manufactured exclusively by Long-Lok, are designed to provide the optimum combination of sealing and fastening in one complete unit. They are cold formed for strength and uniformity, and then assembled with O-rings capable of sealing almost any fluid or gas.


Self-Seal® fasteners overcome all these limitations by placing an O-ring under the head for sealing. With this elegant solution, Self Seal fasteners offer these unique advantages:
• Assemble mating components using standard torque values.
• Specify any common surface finish.
• Metal-to-metal contact.
• High re-usability.
• Positive sealing from either side of the assembly.

Self-Seal fasteners are designed and manufactured with a cold-formed groove beneath the head of the fastener. As the fastener is tightened, the O-ring is compressed, squeezing the O-ring between the groove and mating surface to complete the seal. The design of the groove controls the amount of compression to the O-ring. And because O-rings retain their elastic memory, Self-Seal fasteners are reusable time after time. The O-Ring groove is optional for 100° flathead fasteners. Standard 100° flatheads are without the O-Ring groove.

Typical Applications
• Motors
• Cabinets and enclosures
• Sensors and instrumentation
• Internal combustion engines
• Gear pumps
• Fuel tanks
• Transmissions
• Gear boxes
• Air cylinders
• Pressure gauges
• Computer disk drives
• Motion control valves
• Missile tank
• Wet wings

Military Specifications:

MaterialDescriptionKey UsesTemp. Range
(Dry Heat Only)
Buna-N (Nitrile)Most common seal material. Excellent resistance to petroleum-based oils and fuels, silicone greases, hydraulic fluids, water and alcohols. Low compression set, high tensile strength, and high abrasion resistance.
Oil resistant applications.
Oil resistant applications.

Low temperature military uses.

Automotive, marine, aircraft fuel systems.
-40°F to 250°FBlack
Viton® (Fluorocarbon)High temperature resistance and outstanding chemical resistance. Low gas permeability and high resistance to swelling in gasoline and gasoline/alcohol blends. Resists ozone and U.V. light. Perhaps the “ideal” O-ring material.
Aircraft engine sealing.
Automotive fuel handling systems.Hard vacuum service.

Wide chemical exposure situations.

High temperature/Low compression set applications.
-20°F to 400°FBlack
SiliconeMade from silicone, oxygen, hydrogen and carbon. Excellent retention of flexibility and low compression set characteristics. One of the widest temperature ranges for elastomers.Static seal in extreme temperatures.Medical devices.

Meets FDA regulations.
-75°F to +450°FRed
Ethylene PropyleneCopolymer of ethylene and propylene (EPM), sometimes combined with a third co-monomer (EPDM). Excellent ozone and chemical resistance characteristics. Provides effective resistance to steam (400?F) hot water, silicone oils and greases, dilute acids and alkalies, alcohols and automotive brake fluids.Outdoor weather resistance.Hydraulic and automotive brake systems.

Automobile cooling systems.

Water appliances.
-60°F to +300°FBlack
FluorosiliconeCombines the good high and low temperature stability of Silicone with the fuel, oil, and solvent resistance of Fluorocarbon (Viton®). Suitable for exposure to air, sunlight, ozone, chlorinated and aromatic hydrocarbons.Aerospace fuel systems.Fuel emission control systems.

Static sealing applications.
-70°F to +400°FBlue
Neoprene (Chloroprene)One of the earliest of the synthetic materials to be developed as an oil resistant substitute for natural rubber. A homopolymer of chloroprene (Chlorobutadiene). Good resistance to ozone, sunlight and oxygen aging; low compression set.Components in transportation industry.Recommended for exposure to weathering.

Preferred material for refrigeration industry.

FDA listed for food and beverage industry.
-45°F to +250°FBlack


Long-Lok is part of Novaria Group, a cohesive family of precision component companies, that consistently delivers optimum performance and sustainable growth within the aerospace and defense marketplace.
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