🔩 M3 M4 M5 Socket Head Cap Screws – A2 Stainless Steel, High Strength & Corrosion Resistant
You’re building a 3D printer, assembling a CNC machine, or repairing a piece of industrial equipment – and you need screws that can handle high torque without stripping. These socket head cap screws are made from A2 stainless steel (304), offering excellent corrosion resistance, heat resistance, and high strength. The cylindrical cap head allows deep hex socket engagement, so you can apply serious torque with an Allen key without worrying about cam‑out. Available in M3, M4, and M5 diameters with a range of lengths (select from dropdown). Fully threaded for maximum grip. Perfect for machine tools, electronics enclosures, marine hardware, and any application where a strong, low‑profile fastener is needed.
✨ Key Features – Socket Head Cap Screws (A2 Stainless Steel)
- 🔧 Hex socket (Allen) drive – Allows high torque without cam‑out. Clean, recessed drive won’t collect dirt.
- 🔘 Socket cap head (cylindrical) – Tall head profile provides deep bit engagement and high clamping force.
- 🛡️ A2 stainless steel (304) – Excellent corrosion resistance, oxidation resistance, heat resistance, high strength and toughness.
- 📏 Metric sizes M3, M4, M5 – Popular diameters for 3D printers, machinery, electronics, and marine use.
- 📐 Fully threaded, coarse pitch – Threads run the entire length under the head. Maximum grip in blind holes or with nuts.
- ⚙️ DIN 912 / ISO 4762 standard – Precision dimensions, consistent quality.
- 🔩 Versatile applications – CNC machines, 3D printers, electronic enclosures, furniture, automotive, and marine hardware.
📏 Specifications – M3 M4 M5 Socket Head Cap Screws (A2 Stainless)
| Thread Diameter (M) |
Thread Pitch (mm) |
Typical Lengths (mm, under head) * |
Head Style |
Drive |
Material |
| 📐 Length measured from underside of head to tip (grip length). Fully threaded. Select exact size from dropdown. |
| M3 |
0.5 |
5, 6, 8, 10, 12, 16, 20, 25, 30, 35, 40 |
Socket cap head |
Hex socket (Allen) |
A2 304 Stainless Steel |
| M4 |
0.7 |
5, 6, 8, 10, 12, 16, 20, 25, 30, 35, 40 |
| M5 |
0.8 |
6, 8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50 |
* Lengths are typical – exact availability may vary. Please allow minor manual measurement errors. Hex key sizes: M3→2.5mm, M4→3mm, M5→4mm.
📋 Why A2 Stainless Steel for Socket Cap Screws?
| Property |
Benefit |
| Corrosion resistance |
Excellent – resists rust in outdoor, humid, and coastal environments. No plating needed. |
| Strength |
High tensile strength (A2‑70 ~700 MPa). Withstands high torque without deformation. |
| Heat & oxidation resistance |
Suitable for applications up to moderate temperatures (e.g., engine compartments, industrial equipment). |
| Magnetic |
Almost non‑magnetic (slightly magnetic after cold working – normal for 304). |
❓ Frequently Asked Questions – Socket Head Cap Screws
1. How do I measure the length of a socket head cap screw?
For socket cap head screws, length is measured from the underside of the head (the flat bearing surface) to the tip. The head itself is NOT included. So an “M4 x 10mm” screw has a 10mm long threaded shaft under the head. All our lengths follow this standard.
2. Are these screws fully threaded? What about longer lengths?
Yes – all M3, M4, and M5 screws in this range (up to the maximum length) are fully threaded from under the head to the tip, giving you maximum grip in blind holes or when using nuts.
3. Can I use these screws outdoors? Will they rust?
A2 stainless steel (304) is highly corrosion‑resistant and suitable for outdoor use in most environments – rain, humidity, and coastal areas. For continuous saltwater immersion, consider A4 (316) stainless, but for 3D printers, furniture, and general outdoor use, A2 is excellent and will not rust.
4. What Allen key size do I need for M3, M4, and M5?
M3 uses a 2.5mm hex key, M4 uses 3mm, M5 uses 4mm. Always use a quality hex key that fits snugly to avoid rounding the socket.
5. 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). For outdoor applications, pair with stainless steel nuts to avoid galvanic corrosion.
6. Do you offer other sizes like M6 or M8?
This listing covers M3, M4, M5. We also carry M6, M8, and other sizes in our store – please check our other listings or contact us for custom orders.
