M8 Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021) is the m8-thread variant of Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021) manufactured to GB/T 77 / ISO 4026. This page focuses on the data engineers reach for at the bench: dimensional values for the M8 size, the spanner/drive that fits, and the assembly data you need to install it.
M8 Dimensional Row (GB/T 77 / ISO 4026)
| Size | Pitch (mm) | Length L (mm) | Hex socket s (mm) | Engagement depth t min (mm) | Point diameter dp (mm) | Reference standard |
|---|---|---|---|---|---|---|
| M8 | 1.25 | 12 | 4.0 | 4.0 | 5.5 | ISO 4026-4029 / GB/T 77-79 |
Spanner & Drive for M8 Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021)
The hex socket for M8 Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021) 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 M8
| Coarse-thread pitch (ISO 724) | 1.25 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 9 mm |
| Tapping drill, coarse thread | 6.8 mm |
Tightening Torque for M8
| Class 8.8 (dry, ~µ 0.125) | ≈ 25 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 35 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 41 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 M8 Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021)
M8 Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021) are commonly specified for machine assembly, general engineering, plant maintenance and OEM equipment.
Installation Tips for M8 Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021)
- 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.
When to Step Up or Down from M8
When the joint preload approaches the proof load of M8 class 8.8, step up to M10 class 8.8 (or move to M8 class 10.9). When the joint is over-specified, M6 often saves weight and cost without losing the safety margin.