The M12 size of Hex Head Bolt is dimensioned by GB/T 5782 / ISO 4014. The tables below give the dimensional row from the standard, the drill and spanner sizes that go with it, and the assembly torque per property class. The technical drawing on this page redraws to the exact values selected.
M12 Dimensional Row (GB/T 5782 / ISO 4014)
| Size | Pitch (mm) | Nominal diameter d (mm) | Length L (mm) | Width across flats s (mm) | Width across corners e (mm) | Head height k (mm) |
|---|---|---|---|---|---|---|
| M12 | 1.75 | 12 | 80 | 18.0 | 20.03 | 7.5 |
Spanner & Drive for M12 Hex Head Bolt — GB/T 5782 / ISO 4014 (Series 007)
M12 Hex Head Bolt — GB/T 5782 / ISO 4014 (Series 007) have a width across flats of 18.0 mm — fit a 18.0 mm open-ended spanner or socket. Use a 6-point socket for tight clearances and to reduce rounding; for repeated assembly choose a torque wrench so the joint preload is repeatable.
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 Hex Head Bolt — GB/T 5782 / ISO 4014 (Series 007) Weight
A steel M12 hex head bolt at the listed 80 mm length weighs approximately 88 g each — about 88 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 Hex Head Bolt — GB/T 5782 / ISO 4014 (Series 007)
M12 Hex Head Bolt — GB/T 5782 / ISO 4014 (Series 007) are commonly specified for medium-duty structural connections, automotive sub-frames and equipment chassis.
Installation Tips for M12 Hex Head Bolt — GB/T 5782 / ISO 4014 (Series 007)
- Use a 6-point socket where access allows — 12-point sockets are more prone to rounding the corners on smaller sizes.
- On flanged or serrated variants, do NOT add a separate flat washer — the flange already spreads the load and the washer can defeat the locking serrations.
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.