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When a protruding bolt head is not an option — whether you're assembling electronics enclosures, cabinetry hardware, or precision mechanical components — a standard hex bolt simply won't do. Makers, engineers, and maintenance professionals who need a clean, flush finish rely on countersunk socket cap screws to get the job done right without sacrificing holding strength.
Each screw in this listing is a UNC countersunk (flat-head) socket cap screw machined from A2 stainless steel (304 grade). The flat, angled head is designed to sit flush with or below the mating surface when installed in a properly countersunk hole. Available sizes span from #2-56 through 5/16-18, with lengths ranging from 3/16" (≈4.8 mm) to 2" (≈50.8 mm). Sold in convenient packs of 2, 10, 50, or 100 pieces to match your project scale.
These UNC countersunk machine screws are widely used in electronics panel assembly, aluminum extrusion framing, woodworking jigs, 3D printer builds, and light structural fabrication — anywhere a flush-mount fastener with a hex socket drive is required. The internal hex (Allen) drive allows high torque application in tight spaces where a Phillips or slotted driver would slip.
| Product Type | Countersunk (Flat Head) Socket Cap Screw |
|---|---|
| Drive Type | Internal Hex (Allen / Socket) |
| Head Style | Flat / Countersunk (82° included angle, typical) |
| Thread Standard | UNC — Unified National Coarse |
| Available Diameters | #2-56, #4-40, #6-32, #8-32, #10-24, 5/16-18 |
| Available Lengths | 3/16" (≈4.8 mm) to 2" (≈50.8 mm) — varies by diameter |
| Material | A2 Stainless Steel (Grade 304) |
| Finish | Natural stainless (no coating) |
| Corrosion Resistance | Good — suitable for indoor and light outdoor use |
| Tensile Strength | Typically 500–700 MPa (varies by diameter) |
| Pack Quantities | 2 pcs, 10 pcs, 50 pcs, 100 pcs |
| Hex Key Size | See variant options (varies by screw diameter) |
| Country of Origin | Contact us to confirm |
For countersunk (flat-head) screws, the listed length is the full body length including the head. Measure the total material thickness you need to fasten, then select a length that allows the head to sit flush or just below the surface. For example, a 1/2" (12.7 mm) screw is typically used in material up to about 3/8" thick when countersinking is applied. When in doubt, go slightly longer and countersink deeper.
These screws follow the Unified National Coarse (UNC) thread standard, which is the most common inch-based fastener thread in the United States. They are compatible with standard UNC tapped holes and nuts of the corresponding size — #2-56, #4-40, #6-32, #8-32, #10-24, and 5/16-18.
A2 stainless steel (also known as 304 stainless) is an austenitic grade offering good corrosion resistance and a tensile strength typically around 500–700 MPa depending on size. It is well-suited for general-purpose indoor and light outdoor applications. For highly corrosive marine environments, A4 (316) stainless is generally recommended instead.
Yes, A2 stainless steel provides good resistance to rust and oxidation, making these screws suitable for most outdoor applications such as furniture assembly, enclosures, and light structural work. However, in salt-spray or marine environments, A4 (316) stainless steel is generally a better choice for long-term corrosion resistance.
The required hex key size varies by screw diameter. As a general guide:
Always verify with the specific driver size chart for your fastener before installation.
Choose the quantity based on your project scope. A pack of 2 is ideal for a quick repair or prototype. A pack of 10 suits small assembly jobs or hobby projects. Packs of 50 or 100 offer better per-unit value for production runs, batch builds, or keeping a well-stocked workshop. Larger quantities generally provide a lower cost per screw.
These are inch-standard (UNC) socket cap screws designed for inch-sized hex keys. While some metric hex keys may fit due to close dimensional overlap, using the correct inch-sized Allen key is recommended to avoid rounding the socket drive. These screws are not compatible with metric (M-series) nuts or tapped holes — UNC and metric threads are not interchangeable.
These fasteners are commonly used in electronics panel assembly, aluminum extrusion framing, 3D printer builds, woodworking jigs, machine guards, enclosure fabrication, and any application requiring a flush-mount fastener with a high-torque hex drive. The countersunk head is especially useful where a protruding bolt head would interfere with mating parts or aesthetics.
