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Metric Torx Socket Flat Head Cap Screw – A4 / 316 Stainless Steel, Black Oxide
What is a Metric A4 Stainless Black Oxide Torx Flat Head Cap Screw?
Flat head Torx socket cap screws feature a 90° countersunk underside designed to seat flush with the surface of the workpiece when installed in a properly countersunk hole. The flush installation provides a clean, low-profile finished surface and helps prevent the screw head from protruding above the assembly. Screw length is measured from the top of the head to the tip, including the head.
The Torx (hexalobular) drive provides excellent torque transfer because driving forces are distributed across the six lobes of the recess, providing secure driver engagement and reducing cam-out compared with Phillips-style drives. The design also helps reduce driver wear and makes these screws well suited for controlled assembly applications. These screws are also known as countersunk Torx socket cap screws, six-lobe drive flat head screws, Torx flat head machine screws, and countersunk multi-tooth socket cap screws.
What material is a Metric A4 Stainless Black Oxide Flat Head Cap Screw made from?
These screws are manufactured from A4 stainless steel, also known as AISI 316 or marine-grade stainless steel, providing excellent resistance to corrosion, saltwater, chlorides, moisture, and many chemicals. A4 stainless steel is particularly well suited for demanding outdoor, coastal, and marine environments.
The black oxide finish provides an attractive matte black appearance while retaining the underlying properties and strength of the A4 stainless steel. Black oxide is a surface treatment rather than a conventional thick coating, resulting in practically no dimensional change to the base fastener.
What are the benefits of Black Oxide A4 Stainless Steel?
The black oxide treatment is abrasion resistant and does not peel, chip, or rub off like many conventional coatings. It reduces friction and can help reduce galling during installation while maintaining the strength of the stainless steel. The spray-applied treatment may wear over time, gradually revealing an attractive matte black stainless finish.
Black oxide treatment per MIL-DTL-13924, Class 4 on 300-series corrosion-resistant steel meets 96 hours of resistance in a 5% salt spray (fog) test in accordance with ASTM B117. Stainless steel installation tools are recommended to prevent extraneous rust or contamination during installation.
Why choose an A4 Stainless Black Oxide Torx Flat Head Cap Screw?
These screws combine the flush installation of a 90° countersunk head, high-torque Torx drive, and corrosion resistance of A4 / 316 stainless steel with a distinctive black oxide finish. The countersunk head is ideal where a smooth, unobstructed surface is required, while the Torx recess provides reliable driver engagement during installation.
A4 stainless steel makes these screws especially appropriate for marine, coastal, outdoor, and corrosive environments, while the black oxide finish provides a darker appearance for applications where natural stainless steel is not desired.
Where are A4 Stainless Black Oxide Torx Flat Head Cap Screws commonly used?
A4 stainless black oxide Torx flat head cap screws are commonly used in marine equipment, boats and yachts, automotive and motorsport components, motorcycle assemblies, outdoor machinery, architectural hardware, sporting equipment, industrial machinery, robotics, automation equipment, electrical enclosures, food processing equipment, and OEM manufacturing.
They are particularly useful for flush-mounted panels, brackets, covers, machine components, marine hardware, automotive trim and chassis components, and visible finished assemblies where corrosion resistance, a low-profile installation, and a durable black appearance are important.
