A socket head cap screw — gb/t 5281 / iso 7379 (series 015 in M4: this guide pulls the row from the standard, adds the assembly numbers an engineer actually uses, and links you straight to a quote.
M4 Dimensional Row (GB/T 5281 / ISO 7379)
| Size | Pitch (mm) | Length L (mm) | Head diameter dk (mm) | Head height k (mm) | Hex socket s (mm) | Reference standard |
|---|---|---|---|---|---|---|
| M4 | 0.7 | 25 | 7.0 | 4 | 3.0 | ISO 4762 / GB/T 70.1 |
Spanner & Drive for M4 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 015)
The hex socket for M4 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 015) is shown in the spec table — use the matching Allen / hex key (an ISO 2936 hex key set covers the full range). A T-handle Allen key gives the best feel for setting preload by feel; for production work use a torque-controlled driver.
Hole Sizes for M4
| Coarse-thread pitch (ISO 724) | 0.7 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 4.5 mm |
| Tapping drill, coarse thread | 3.3 mm |
Tightening Torque for M4
| Class 8.8 (dry, ~µ 0.125) | ≈ 2.9 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 4.1 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 4.9 Nm |
Indicative dry-joint values. Lubrication can lower the required torque by 15–25%. Always confirm against the joint design, especially when going up a strength class.
Common Applications for M4 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 015)
M4 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 015) are commonly specified for electronics, PCB hardware, optical mounts and small-scale machinery.
Installation Tips for M4 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 015)
- Use a quality Allen key fully seated in the socket — partial engagement is the most common cause of stripped sockets at this size.
- For countersunk and button-head variants, chamfer the through-hole to seat the head flush without preloading the head/shank fillet.
- At M4 the joint is sensitive to over-torque — use a torque-limiting driver and check the head doesn't bury into a softer counterpart.
Mating Parts for M4
For M4, pair with a M4 hex nut (ISO 4032 / DIN 934) and, where used, a M4 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.