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MS51957-44 – Stainless Steel Pan Head Phillips Machine Screw
Available now through the AirParts Aero marketplace.
Overview Section
The MS51957-44 is a high-grade Corrosion-Resistant Steel (CRES) machine screw featuring a pan head and a Phillips drive. As a Military Standard (MS) fastener, it is manufactured to stringent aerospace and defense tolerances, ensuring consistency in material strength, thread precision, and finish.
The MS51957 series is the stainless steel equivalent to the alloy steel MS35206 series. Because it is made from 300-series stainless steel, this screw is non-magnetic and highly resistant to oxidation, making it the ideal choice for instrument panels, cabin interiors, and external components exposed to moisture or corrosive environments.
Key Features Section
Corrosion-Resistant Steel (300 Series): Provides excellent protection against rust and environmental degradation without the need for additional plating.
Pan Head Profile: Features a flat top surface with rounded sides, providing a large bearing surface and a clean, professional appearance.
Phillips Drive (Type I): Compatible with standard cross-recess screwdrivers, allowing for high-torque manual installation while minimizing the risk of tool "cam-out."
Non-Magnetic Property: Ideal for use in and around cockpit instrument panels and magnetic compasses where magnetic interference must be avoided.
Passivated Finish: Treated to remove surface impurities and enhance the natural protective oxide layer of the stainless steel.
Unified Fine Thread (UNF): Features precision-rolled threads for a secure fit and high resistance to vibration-induced loosening.
Technical Specifications Section
| Specification | Detail |
| Part Number | MS51957-44 |
| Thread Size | 8-32 UNC-2A (Nominal) |
| Length | 0.500 in (1/2 inch) |
| Material | 300 Series Corrosion-Resistant Steel (CRES) |
| Head Style | Pan Head |
| Drive Type | Phillips (Recess) |
| Thread Class | 2A (Standard Fit) |
| Finish | Passivated (per AMS2700) |
Aircraft Compatibility Section
The MS51957-44 is a "standard hardware" item found in virtually all aircraft types:
General Aviation (Cessna/Piper/Beech): Used for mounting avionics, securing interior fairings, and attaching inspection plates.
Cockpit Instrument Panels: The primary fastener for securing 3-1/8" and 2-1/4" flight instruments to the panel.
Corporate Jets (Citation/Learjet): Found in cabin cabinetry and environmental control system (ECS) vent covers.
Experimental Aircraft: A staple for builders requiring durable, non-rusting hardware for nutplate-reinforced assemblies.
Technical Applications & Safety
Stainless steel fasteners are valued for their longevity, but they have different mechanical properties than alloy steel "Structural" screws (like the MS27039 series).
Safety Warning: Do Not Use for Primary Structural Loads. Unless specifically called for in the Maintenance Manual, the MS51957-44 should not be used in high-shear structural applications (such as wing-to-fuselage joints). While strong, 300-series stainless steel has a lower shear strength than heat-treated alloy steel. Additionally, when installing into stainless steel nutplates, use a small amount of Anti-Seize to prevent "galling" (cold-welding), which can occur when two stainless surfaces are torqued together.
Technical Engineering Insight
The engineering value of the MS51957-44 lies in its Passive Protection. Unlike cadmium-plated steel fasteners that eventually rust once the plating is scratched, the 300-series stainless steel is corrosion-resistant throughout its entire cross-section. This is critical for "blind" installations behind panels where moisture may accumulate. Furthermore, the Pan Head geometry is designed to distribute the "clamping force" over a wider area of the sheet metal or plastic fairing than a round head screw, reducing the likelihood of cracking the material around the screw hole.
Installation & Maintenance Addendum
Tooling: Use a high-quality #2 Phillips screwdriver. A worn-out bit will "cam out" of the stainless recess more easily, which can burr the screw head and make it difficult to remove in the future.
Hole Clearance: Ensure the screw passes through the clearance hole without force. If the threads "bite" into the skin of the aircraft, it can lead to localized stress corrosion cracking.
Torque: For 8-32 stainless screws, the standard torque is typically between 12 and 15 inch-pounds. Over-torquing can lead to the head shearing off or the threads stripping in aluminum nutplates.
