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AN525-10R12 – High-Strength Washer Head Machine Screw
Available now on the Airparts.aero Marketplace.
The AN525-10R12 is a specialized, high-strength aerospace fastener designed for structural and semi-structural applications. Belonging to the AN525 series, this screw is distinctive for its integrated washer head, which provides a larger bearing surface than a standard machine screw. This design eliminates the need for a separate flat washer, reducing part count and ensuring an even distribution of clamping force—critical when fastening thin-skin aluminum panels, fairings, or composite structures.
Manufactured from heat-treated alloy steel, the AN525-10R12 is significantly stronger than standard commercial hardware or the common AN526 series. It is typically finished with cadmium plating to prevent corrosion and provide the necessary lubricity for precise torque application in aviation maintenance.
Key Features
Integrated Washer Head: The oversized head diameter prevents "pull-through" on soft materials and provides a clean, professional finish on visible exterior panels.
125,000 PSI Tensile Strength: Heat-treated to aerospace structural standards, making it suitable for high-stress areas where vibration and shear loads are present.
Cadmium Plated (Type II, Class 3): Offers superior sacrificial corrosion protection, particularly important when used in dissimilar metal joints (e.g., steel screw into an aluminum nut plate).
Cruciform (Phillips) Drive: Designed for high-torque manual or pneumatic installation while minimizing the risk of tool "cam-out."
Precision Threads: Features a #10-32 UNF-3A fine thread profile for maximum stripping resistance and vibrational security.
Technical Specifications
Part Number: AN525-10R12
Series: AN525 (Washer Head Machine Screw)
Thread Size: #10-32 (0.1900" - 32 Fine Thread)
Screw Length: 0.750" (3/4 inch) — Measured from under the head to the tip.
Material: Alloy Steel (MIL-S-6049 or equivalent)
Finish: Cadmium Plated per QQ-P-416
Head Type: Washer Head (Phillips Drive)
Tensile Strength: 125,000 psi Minimum
Aircraft Compatibility
General Aviation: Standard hardware for Cessna, Piper, and Beechcraft engine baffles, interior floorboards, and fairing attachments.
Commercial & Military: Used in Boeing, Airbus, and Lockheed secondary structures and accessibility panels.
Experimental Aircraft: The preferred fastener for builder kits (e.g., Vans RV series) due to its high strength and integrated washer.
Note: The "R" in the part number indicates a specific grip/length variation in newer nomenclature, though in the legacy AN system, the numbers following the dash represent the diameter and length ($10 = \#10$ diameter, $12 = 12/16$ or $3/4$ inch length).
Applications
The AN525-10R12 is utilized for Panel Fastening and Component Mounting. Its primary roles include:
Fairing and Cowling Attachment: Securing exterior aerodynamic skins where a large bearing area is required to prevent cracking.
Engine Baffle Mounting: Resisting the high-frequency vibration and thermal expansion found in the engine compartment.
Interior Monument Tie-downs: Fastening galleys, partitions, or floor panels to the primary airframe structure.
Why Choose AN525-10R12?
Choosing the genuine AN525-10R12 ensures Fastener Joint Integrity. Standard machine screws can "countersink" themselves into soft aluminum if over-torqued, leading to stress risers and eventual panel failure. The AN525 design spreads the load over a wider area, maintaining the Elastic Preload of the joint more effectively. Because it is heat-treated alloy steel, it will not "neck down" or shear under the G-loads experienced during turbulence or hard landings, unlike common stainless steel (AN526-C) or brass hardware.
The AN525-10R12 functions as a Tension-Loaded Fastener governed by the physics of Clamping Force ($F$). The integrated washer head increases the Effective Bearing Area ($A_b$), which significantly reduces the Bearing Stress ($\sigma_b$) on the parent material ($\sigma_b = F / A_b$). This is vital for thin-gauge aluminum airframes where the material's yield strength is the limiting factor. The use of fine threads (#10-32) allows for a higher Mechanical Advantage, ensuring that the fastener reaches its required tension with less applied torque, thereby reducing the risk of stripping the threads in aluminum nut plates or gang channels.
Note: This is a structural fastener. Never substitute an AN525 alloy steel screw with a standard hardware store screw or even a stainless steel aviation screw (AN526C) without engineering approval, as the tensile strengths are significantly different. Always use a calibrated screwdriver and verify the torque values in the Aircraft Maintenance Manual (AMM) or AC 43.13-1B.
