🔩 M3 M4 M5 Hex Socket Cap Head Screws – Black A2 Stainless Steel, Allen Drive
You’re putting together a 3D printer, mounting a part on your motorcycle, or building a piece of custom furniture – and you want fasteners that look as good as they perform. These black oxide‑finished socket cap screws are made from A2 stainless steel, then coated with electrophoresis black for a sleek, corrosion‑resistant finish that won’t flake or rust easily. The hex socket (Allen) drive lets you apply high torque without stripping, and the cylindrical head gives a clean, professional look. Available in M3, M4, and M5 thread diameters, with a range of lengths to suit your project. Whether you’re a machinist, a hobbyist, or a DIY builder, these black stainless screws add a stealthy accent while delivering the strength you expect from socket head cap screws.
✨ Key Features – Black A2 Stainless Hex Socket Cap Head Screws
- 🔘 Socket cap head design – High cylindrical head with a recessed hex drive. Provides excellent torque transfer and a clean, industrial look.
- ⚫ Electrophoresis black finish – A durable black coating that bonds to the stainless steel. Resists corrosion, scratches, and gives a stealth matte appearance.
- 🛡️ A2 stainless steel base (304) – The underlying material is corrosion‑resistant stainless, so even if the black coating wears, the screw won’t rust easily.
- 🔧 Hex socket (Allen) drive – Allows precise torquing with standard hex keys. Less prone to cam‑out compared to Phillips or slotted drives.
- 📏 Metric sizes M3, M4, M5 – Three commonly used diameters for electronics, machinery, furniture, and automotive applications.
- 📐 Multiple lengths available – Choose from a variety of lengths under the head (e.g., 6mm, 8mm, 10mm, 12mm, 16mm, 20mm, 25mm, 30mm – see dropdown for exact options).
- 💪 Fully threaded (most lengths) – Threads run the full length under the head for maximum grip in blind holes or through‑holes with nuts.
📏 Available Sizes – Black Socket Cap Head Screws (Metric)
| Thread Diameter |
Typical Lengths Available (mm, under head) |
Recommended Hex Key Size |
| M3 |
6, 8, 10, 12, 16, 20, 25, 30 |
2.5 mm |
| M4 |
6, 8, 10, 12, 16, 20, 25, 30, 35, 40 |
3 mm |
| M5 |
8, 10, 12, 16, 20, 25, 30, 40, 50 |
4 mm |
📐 Length is measured from under the head to the tip. Fully threaded for lengths up to 30mm; longer sizes may have partial thread.
📋 Full Specifications – Black A2 Stainless Socket Cap Screws
| Parameter |
Details |
| Product name |
Hex Socket Cap Head Machine Screws / Bolts |
| Material |
A2 Stainless Steel (304 / 18-8) with electrophoresis black coating |
| Head style |
Socket cap head (cylindrical, high profile) |
| Drive style |
Hex socket (Allen key) |
| Thread sizes |
M3, M4, M5 (metric coarse thread) |
| Length range |
6mm – 50mm (varies by diameter – see dropdown) |
| Finish |
Electrophoresis black – matte, uniform, corrosion resistant |
| Grade equivalent |
A2-70 (approx.) |
| Typical applications |
3D printers, CNC machines, automotive trim, furniture, electronics, DIY projects |
❓ Frequently Asked Questions – Black Socket Cap Screws
1. Is the black coating durable? Will it scratch off easily?
Electrophoresis black is a robust coating that bonds electrochemically to the stainless steel. It resists minor scratches and abrasion better than spray paint. However, heavy torque or contact with sharp metal may expose the underlying stainless. Even if scratched, the A2 stainless underneath won’t rust – so the screw remains functional and corrosion‑free.
2. Are these screws fully threaded?
For M3, M4, and M5 lengths up to about 25–30mm, they are typically fully threaded. Longer screws (e.g., 40mm or 50mm) may have a partial thread (unthreaded shank) near the head. If you need full thread on a longer screw, please contact us to check availability.
3. What hex key do I need for M3, M4, and M5?
Standard metric hex key sizes: M3 uses 2.5mm, M4 uses 3mm, M5 uses 4mm. Always use a good quality key that fits snugly to avoid rounding the socket.
4. Can I use these screws outdoors?
Yes – A2 stainless provides good corrosion resistance for outdoor use. The black coating adds extra protection against moisture and UV. However, for continuous saltwater exposure, we recommend uncoated A4 (316) stainless. For normal garden furniture, bike accessories, or outdoor signs, these are perfect.
5. Do these screws come with matching nuts or washers?
This listing is for screws only. We sell matching black stainless or plain stainless nuts and washers separately. Look for “M3/M4/M5 black hex nut” or contact us for a complete fastener kit.
6. What’s the difference between a socket cap head and a button head?
Socket cap heads are taller and cylindrical, providing a larger hex socket for higher torque. Button heads are low profile and rounded. Cap heads are preferred for high‑strength clamping; button heads are for low‑profile aesthetics. This listing is for standard socket cap heads.
