The M5 size of Square Nut, Metric is dimensioned by GB/T 39 / ISO 4034. The table below gives the dimensional row from the standard, followed by the drive and the installation notes for this type.
M5 Dimensional Row (GB/T 39 / ISO 4034)
| Size | Pitch (mm) | Width across flats s (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|
| M5 | 0.8 | 8.0 | 2.7 | GB/T 39 / DIN 562 |
Spanner & Drive for M5 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076)
Drive geometry for M5 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076) is given by the row above; match the tool to the listed values.
Tightening Torque for M5
| Class 8.8 (dry, ~µ 0.125) | ≈ 5.8 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 8.1 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 9.7 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 M5
| Tensile stress area As (ISO 898-1) | 14.2 mm² |
|---|---|
| Proof load, class 8.8 | 8.2 kN |
| Proof load, class 10.9 | 11.8 kN |
| Proof load, class 12.9 | 13.8 kN |
| Min. ultimate tensile, class 8.8 | 11.4 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.
Common Applications for M5 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076)
M5 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076) are commonly specified for paired with the same-size screws on PCB hardware, light enclosures and small-scale assemblies.
Installation Tips for M5 Square Nut, Metric — GB/T 39 / ISO 4034 (Series 076)
- At M5 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 M5
When the joint preload approaches the proof load of M5 class 8.8, step up to M6 class 8.8 (or move to M5 class 10.9). When the joint is over-specified, M4 often saves weight and cost without losing the safety margin.
