For Slotted Countersunk Head Screw — GB/T 68 / ISO 2009 (Series 039), the M4 thread sits in the small-to-medium range of the catalog and is one of the most-asked slotted countersunk head screw — gb/t 68 / iso 2009 (series 039) in this family. The dimensional and assembly data follow.
M4 Dimensional Row (GB/T 68 / ISO 2009)
| Size | Pitch (mm) | Length L (mm) | Head diameter dk (mm) | Head height k (mm) | Cross recess | Countersink angle (deg) | Reference standard |
|---|---|---|---|---|---|---|---|
| M4 | 0.7 | 25 | 7.5 | 2.2 | PH2 | 90 | ISO 7046 / GB/T 819 |
Spanner & Drive for M4 Slotted Countersunk Head Screw — GB/T 68 / ISO 2009 (Series 039)
The hex socket for M4 Slotted Countersunk Head Screw — GB/T 68 / ISO 2009 (Series 039) 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 Slotted Countersunk Head Screw — GB/T 68 / ISO 2009 (Series 039)
M4 Slotted Countersunk Head Screw — GB/T 68 / ISO 2009 (Series 039) are commonly specified for electronics, PCB hardware, optical mounts and small-scale machinery.
Installation Tips for M4 Slotted Countersunk Head Screw — GB/T 68 / ISO 2009 (Series 039)
- 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.
When to Step Up or Down from M4
When the joint preload approaches the proof load of M4 class 8.8, step up to M5 class 8.8 (or move to M4 class 10.9). When the joint is over-specified, M3 often saves weight and cost without losing the safety margin.