Dimensional data for M20 Square Nut to GB/T 39 / ISO 4034, with the drive and the installation notes for this type. Values are taken from the governing standard rather than from a general machine-thread table, because this type is not selected on one.
M20 Dimensional Row (GB/T 39 / ISO 4034)
| Size | Pitch (mm) | Width across flats s (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|
| M20 | 2.5 | 30.0 | 12.0 | GB/T 39 / DIN 562 |
Spanner & Drive for M20 Square Nut — GB/T 39 / ISO 4034 (Series 075)
Drive geometry for M20 Square Nut — GB/T 39 / ISO 4034 (Series 075) is given by the row above; match the tool to the listed values.
Tightening Torque for M20
| Class 8.8 (dry, ~µ 0.125) | ≈ 410 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 580 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 690 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 M20
| Tensile stress area As (ISO 898-1) | 245 mm² |
|---|---|
| Proof load, class 8.8 | 147 kN |
| Proof load, class 10.9 | 203 kN |
| Proof load, class 12.9 | 238 kN |
| Min. ultimate tensile, class 8.8 | 196 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 M20 Square Nut — GB/T 39 / ISO 4034 (Series 075)
M20 Square Nut — GB/T 39 / ISO 4034 (Series 075) are commonly specified for structural joints, flange connections and heavy equipment foundations.
Installation Tips for M20 Square Nut — GB/T 39 / ISO 4034 (Series 075)
- At M20 the stretch in the bolt becomes the controlling factor — for critical joints, use angle-controlled or stretch-controlled tightening instead of pure torque.
Mating Parts for M20
Pair M20 with the matching M20 bolt or screw, plus a M20 flat washer where required to distribute load on softer materials.
