M83248/2-905 – Aerospace Preformed Fluorocarbon Rubber O-Ring Packing
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Overview
The M83248/2-905 is a flight-critical, military-standard preformed packing O-ring, an essential sealing component for aerospace hydraulic and fuel systems. This is not a standard O-ring; it is a specialized boss gasket seal engineered in strict accordance with the MIL-DTL-83248/2 specification. The /2 designator specifies that this seal is fabricated from a high-performance, 75-durometer Fluorocarbon (FKM) elastomer, commonly known as Viton®. The -905 dash number indicates its specific dimensions for sealing a -5 AN/JIC straight thread tube fitting.
Its primary function is to create a positive, leak-proof static seal between a straight thread fitting and its corresponding port, or "boss." As a genuine military-specification component, it guarantees the material performance and dimensional accuracy required for high-pressure, high-temperature fluid systems.
Key Features
High-Temperature Fluorocarbon (FKM) Material: Fabricated from a 75-durometer Viton® (FKM) elastomer. This material provides superior performance in high-temperature environments (up to 400°F) and is the industry standard for systems using synthetic hydraulic fluids, jet fuels, and oils.
Boss Gasket Seal Design: The -900 series dash number signifies that this is a specialized O-ring designed to be used as a gasket for a straight thread tube fitting boss. It is installed in the groove of the male fitting to create a static face seal when torqued into a port.
Excellent Fluid Resistance: Offers exceptional resistance to a wide array of aggressive fluids, including synthetic turbine oils (MIL-PRF-23699), petroleum-based oils, jet fuels, and both petroleum-based (MIL-H-5606) and synthetic phosphate-ester (Skydrol) hydraulic fluids.
Mil-Spec Certified Quality: As a certified military specification part, it guarantees full material traceability, dimensional accuracy, and performance characteristics (like compression set resistance) that meet the highest standards for safety and airworthiness.
Color Coded for Identification: The MIL-DTL-83248/2 standard often specifies a distinct color (such as black or brown) to identify the specific FKM compound and durometer, preventing incorrect installation.
Technical Specifications
Standard: M83248/2 (MIL-DTL-83248/2)
Full Part Number: M83248/2-905
Component Type: Boss Gasket O-Ring Seal for Straight Thread Tube Fitting
Material: Fluorocarbon Rubber (FKM / Viton®)
Durometer (Hardness): 75 Shore A
AS3579 Dash Size: -905 (for -5 AN / 1/2-20 thread size)
Precise Dimensions:
Inside Diameter (I.D.): 0.421 inches (approx. 27/64")
Cross Section (C.S.): 0.064 inches (approx. 1/16")
Operating Temperature Range: Approximately -15°F to 400°F (-26°C to 204°C)
Aircraft Compatibility
The M83248/2-905 is a universal sealing component used on virtually all modern military, commercial, and business aircraft where -5 AN straight thread fittings are used in high-temperature fuel, oil, or synthetic hydraulic fluid systems.
Common System Applications:
Hydraulic Systems: Sealing connections on actuators, pumps, valves, and manifolds, especially on systems using Skydrol.
Fuel Systems: Sealing high-pressure fuel line fittings, particularly in firewall-forward applications.
Engine & APU Lubrication Systems: Providing seals for oil filters, sensors, and other components using synthetic turbine oil.
Textron Aircraft:
Cessna Stationair
Cessna Skylane
Why Choose M83248/2-905?
A leak in a high-pressure hydraulic or fuel system is a critical flight emergency. The M83248/2-905 is the only seal certified to perform reliably in these demanding systems. Its FKM material is specifically engineered to resist the aggressive synthetic fluids and high temperatures that would cause standard Nitrile (Buna-N) O-rings to swell, harden, and fail. Using a genuine, certified mil-spec part is the only way to ensure the seal has the correct material properties and precise dimensions for a safe, leak-proof, and airworthy connection.
The M83248/2-905 is a key component of a straight thread O-ring boss seal. This design is superior to tapered pipe threads for high-pressure aerospace applications because it is far more resistant to leakage from vibration and pressure impulses. The seal is not made by the threads themselves, but by the O-ring. The M83248/2-905 O-ring is installed in a groove on the male fitting. When the fitting is tightened into a female port (boss), the O-ring is compressed radially against the tapered seat of the boss, creating a highly reliable, contained seal. The straight threads of the fitting only provide the mechanical clamping force; they are not part of the seal itself. The Fluorocarbon (FKM) material is essential here, as its excellent "compression set resistance" ensures the O-ring continues to exert a positive sealing force even after prolonged compression at high temperatures, preventing leaks that would develop with lesser materials.
Note: This is a single-use, flight-critical sealing component. It must be replaced whenever the fitting it seals is removed. Ensure all sealing surfaces are meticulously clean, dry, and free of nicks or scratches before installation. Lubricate the O-ring with a clean, compatible system fluid before assembly to prevent damage. Do not use tools that could damage the seal.