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When a protruding screw head gets in the way — snagging cables, blocking panels, or ruining a clean surface — you need a fastener that disappears into the material. These A2 stainless steel countersunk socket screws are built for makers, engineers, and DIYers who demand a flush, professional result without compromise. Whether you're assembling electronics enclosures, CNC-machined parts, or furniture frames, the right flat-head hex bolt makes all the difference.
Each screw features a 90° countersunk flat head with an Allen hex drive socket, machined from A2 (304) stainless steel for reliable corrosion resistance. Sizes span M2 through M12, with lengths ranging from 3mm to 100mm depending on diameter — covering the vast majority of metric fastening needs. Available in convenient 10-piece or 50-piece packs so you can stock exactly what your project requires.
These metric countersunk hex bolts are a go-to choice for 3D printer frames, electronics enclosures, aluminum extrusion builds, cabinetry hardware, and general mechanical assembly. The ISO metric coarse thread ensures compatibility with standard nuts, threaded inserts, and tapped holes across all common M-series designations.
| Material | A2 Stainless Steel (equivalent to 304 SS) |
|---|---|
| Head Style | Countersunk Flat Head (90° included angle) |
| Drive Type | Hex Socket (Allen / Internal Hex) |
| Thread Standard | ISO Metric Coarse Thread |
| Diameter Range | M2, M2.5, M3, M4, M5, M6, M8, M10, M12 |
| Length Range | 3mm (≈1/8") to 100mm (≈3.9") — varies by diameter |
| Finish | Bright / Natural Stainless (uncoated) |
| Property Class | Typically Class 70 (≈700 MPa tensile strength) |
| Hex Key Size | See variant options (varies by screw diameter) |
| Pack Quantity | 10 pieces or 50 pieces (select above) |
| Compatibility | Standard metric nuts, threaded inserts, tapped holes |
| Recommended Use | Electronics, machinery, furniture, DIY, 3D printers, CNC frames |
A general rule of thumb is that the screw should engage the base material by at least 2–3 times the screw diameter. For example, an M4 screw typically needs at least 8–12mm of thread engagement in the base material. Remember to account for the countersink depth — the flat head sits below the surface, so the effective clamping length is the total screw length minus the head depth. When in doubt, go slightly longer and trim or select the next size down.
A2 stainless steel is the ISO designation for 304 stainless steel, containing approximately 18% chromium and 8% nickel. It offers good corrosion resistance for most indoor and light outdoor applications. A4 stainless steel (316 SS) adds molybdenum for enhanced resistance to chlorides and salt — making it the better choice for marine or coastal environments. For typical workshop, home, and electronics use, A2 is generally sufficient.
A2 stainless steel generally handles light outdoor exposure well — rain, humidity, and mild temperature swings are typically not a problem. However, in environments with heavy salt air, chlorine exposure, or constant moisture (such as coastal or marine settings), A4 (316) stainless steel is usually recommended for longer service life. For most outdoor DIY and garden furniture applications, A2 performs reliably.
The required hex key size generally corresponds to the screw diameter as follows (typical values — verify with your specific fastener):
Yes. These screws use standard ISO metric coarse thread, which is the most common thread standard for metric fasteners worldwide. They are compatible with standard metric hex nuts, nylon lock nuts, heat-set threaded inserts, and tapped holes of the same M-size designation. Common thread pitches: M3×0.5, M4×0.7, M5×0.8, M6×1.0, M8×1.25, M10×1.5, M12×1.75.
A countersunk (flat head) screw has a tapered underside that seats into a matching countersunk hole, allowing the head to sit flush with or below the surface. This is ideal when you need a smooth, snag-free surface. A pan head screw has a low-profile rounded head that sits above the surface — good for clamping thin materials. A button head has a dome-shaped low-profile head, also sitting above the surface. Choose countersunk when flush mounting is required.
A2 stainless steel socket screws are generally rated to property class 70, with a tensile strength of approximately 700 MPa. They are well-suited for general mechanical assembly, electronics enclosures, furniture, and light machinery. For safety-critical or high-load structural applications, we recommend consulting a qualified engineer and verifying load requirements against the specific fastener's rated capacity.
Yes — for a proper flush fit, you need to drill a clearance hole matching the screw's nominal diameter, then use a 90° countersink bit to create the tapered recess for the head. The countersink depth should match the head height of the screw so the top of the head sits level with the surface. In softer materials like wood or plastic, the head may self-countersink slightly, but pre-drilling is always recommended for accuracy and to avoid splitting.
