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M4 set screw size
2 mm hex key
Allen / internal hex key size for M4 grub
M4 set screw — collars, pulleys and knobs.
Full specification
| System | Metric (45H) |
| Nominal diameter | 4 mm |
| Thread pitch | 0.7 mm |
| Hex key (Allen) | 2 mm |
| Tap drill | 3.3 mm |
| Clearance hole | n/a (threaded) |
| Common grade / class | 45H |
| Typical torque | 1.8 Nm (1.3 ft·lb) |
| Closest other-system size | ~#8 imperial |
🔧 Torque unit converter
Pre-filled with the typical torque for M4 grub (45H, dry). Edit any field to convert.
⚠️ Torque values here are general references for 45H 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 grub
M4 grub screws hold pulleys and collars on small shafts.
A dab of thread locker stops M4 grubs vibrating loose on rotating shafts.
Frequently asked questions
- What size Allen / hex key fits M4 grub?
- M4 set screw uses a 2 mm hex (Allen) key with an internal hex drive.
- What is the torque for M4 grub?
- A typical tightening torque for M4 set screw in 45H on dry threads is about 1.8 Nm (1.3 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does M4 grub use?
- M4 set screw has a thread pitch of 0.7 mm and uses a 3.3 mm tap drill, with a n/a (threaded) clearance hole.