Dimensional and assembly data for M12 Socket Head Cap Screw to GB/T 5281 / ISO 7379. Includes head size and width across flats, clearance-hole and tapping-drill diameters, tightening torque per property class, and the sizes to step up or down to when the joint requires it.
M12 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 |
|---|---|---|---|---|---|---|
| M12 | 1.75 | 80 | 18.0 | 12 | 10.0 | ISO 4762 / GB/T 70.1 |
Spanner & Drive for M12 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 016)
The hex socket for M12 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 016) 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 M12
| Coarse-thread pitch (ISO 724) | 1.75 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 13.5 mm |
| Tapping drill, coarse thread | 10.2 mm |
Tightening Torque for M12
| Class 8.8 (dry, ~µ 0.125) | ≈ 85 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 120 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 145 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.
Proof Load & Strength for M12
| Tensile stress area As (ISO 898-1) | 84.3 mm² |
|---|---|
| Proof load, class 8.8 | 49 kN |
| Proof load, class 10.9 | 70 kN |
| Proof load, class 12.9 | 82 kN |
| Min. ultimate tensile, class 8.8 | 67 kN |
Proof load = stress area × proof stress per ISO 898-1. Design joints so the working preload stays below the proof load of the selected class.
M12 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 016) Weight
A steel M12 socket head cap screw at the listed 80 mm length weighs approximately 160 g each — about 160 kg per 1,000 pieces. Stainless A2/A4 weighs roughly the same (density 7.9–8.0 g/cm³). Actual weight varies slightly with head form, thread and finish; use this figure for freight estimation only.
Common Applications for M12 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 016)
M12 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 016) are commonly specified for heavier machine assembly and equipment mounting.
Installation Tips for M12 Socket Head Cap Screw — GB/T 5281 / ISO 7379 (Series 016)
- 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 M12
When the joint preload approaches the proof load of M12 class 8.8, step up to M16 class 8.8 (or move to M12 class 10.9). When the joint is over-specified, M10 often saves weight and cost without losing the safety margin.