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You’re building a custom PC, mounting black anodized aluminum panels, or working on a project where dark hardware is a must – and you want screws that disappear into the surface. These M3, M4, and M5 hex socket countersunk screws are made from A2 stainless steel with an electrophoresis black finish. The flat 90° head sinks flush into a pre‑drilled countersink, leaving a smooth, almost invisible finish. The hex socket (Allen) drive lets you apply torque without slipping. Available in lengths from 5mm to 30mm measured overall (including the head). Fully threaded. The black coating is durable and adds extra corrosion resistance. Perfect for marine equipment, outdoor electronics, automotive trim, and any project where a low‑profile, rust‑proof dark screw is needed.
| Thread Diameter (M) | Thread Pitch (mm) | Overall Length (mm, including head) * | Head Style | Drive | Hex Key Size (mm) | Material / Finish |
|---|---|---|---|---|---|---|
| 📐 Overall length = from top of head to tip. Fully threaded. Select exact size from dropdown. | ||||||
| M3 | 0.5 | 5, 6, 8, 10, 12, 16, 20, 25, 30 |
Countersunk / Flat (90°) |
Hex socket (Allen) |
2 mm |
A2 304 Stainless / Electrophoresis black |
| M4 | 0.7 | 5, 6, 8, 10, 12, 16, 20, 25, 30 | 2.5 mm | |||
| M5 | 0.8 | 5, 6, 8, 10, 12, 16, 20, 25, 30 | 3 mm | |||
* Lengths are typical – exact availability may vary. Please allow minor manual measurement errors. Black color may vary slightly due to monitor calibration.
| Property | Details |
|---|---|
| Standard | GB/T 70.3 / ISO 10642 / DIN 7991 – metric countersunk hex socket head screws |
| Material | A2 stainless steel (304) – excellent corrosion resistance, high strength, non‑magnetic (slightly after cold working) |
| Finish | Electrophoresis black – uniform matte black coating, good adhesion, salt spray resistance |
| Thread | Coarse metric, fully threaded, burr‑free |
1. How do I measure the length of these countersunk screws?
For countersunk flat head screws (DIN 7991), the length is measured overall – from the top of the head to the tip. So an “M4 x 10mm” screw has a total length of 10mm including the head. This matches our listing.
2. Do I need to countersink the hole for these screws to sit flush?
Yes – these are true 90° countersunk screws. To achieve a flush or slightly recessed finish, you must drill a matching 90° countersink hole. Use a countersink bit slightly larger than the head diameter.
3. Are these screws fully threaded?
Yes – all M3, M4, and M5 screws in this range (up to 30mm overall length) are fully threaded from under the head to the tip, giving you maximum grip in blind holes or through‑nut applications.
4. Will the black coating scratch or wear off? What about rust?
Electrophoresis black is a durable coating that bonds to the steel. It resists scratches better than paint, but heavy torque or contact with sharp metal may leave marks. The good news: the base material is A2 stainless steel. Even if the coating wears, the screw itself will not rust – a major advantage over black‑coated carbon steel screws.
5. What hex key size do I need for M3, M4, and M5?
M3 uses a 2mm Allen key, M4 uses 2.5mm, M5 uses 3mm. Always use a quality hex key that fits snugly to avoid rounding the socket.
6. Can I use these screws with a nut? What size nut fits?
Yes – these are machine screws. Use standard metric nuts of the same thread size (M3, M4, or M5). We recommend matching black or stainless nuts. They will also thread into pre‑tapped holes. Not self‑tapping – for wood or plastic, use a threaded insert or a nut on the back.
