Home › Socket Cap Screws › M4 socket cap
M4 socket cap screw size
3 mm hex key
Allen / internal hex key size for M4 socket cap
M4 socket cap screw — machine guards and fixtures.
Full specification
| System | Metric (12.9) |
| Nominal diameter | 4 mm |
| Thread pitch | 0.7 mm |
| Hex key (Allen) | 3 mm |
| Tap drill | 3.3 mm |
| Clearance hole | 4.5 mm |
| Common grade / class | 12.9 |
| Typical torque | 4.5 Nm (3.3 ft·lb) |
| Closest other-system size | ~#8 imperial |
🔧 Torque unit converter
Pre-filled with the typical torque for M4 socket cap (12.9, dry). Edit any field to convert.
⚠️ Torque values here are general references for 12.9 on clean, dry threads. Lubrication, coatings, and the joint material change the figure significantly. For structural, automotive, or safety-critical work, always use the torque specified by the manufacturer or engineer.
About M4 socket cap
M4 socket caps are common in machine fixtures and electronic enclosures.
A 3 mm hex key fits M4 — do not force a worn key or you will round the socket.
Frequently asked questions
- What size Allen / hex key fits M4 socket cap?
- M4 socket cap screw uses a 3 mm hex (Allen) key with an internal hex drive.
- What is the torque for M4 socket cap?
- A typical tightening torque for M4 socket cap screw in 12.9 on dry threads is about 4.5 Nm (3.3 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does M4 socket cap use?
- M4 socket cap screw has a thread pitch of 0.7 mm and uses a 3.3 mm tap drill, with a 4.5 mm clearance hole.