The M18 size of Hexagon Coupling Nuts is dimensioned by DIN 6334. The table below gives the dimensional row from the standard, followed by the drive and the installation notes for this type.
M18 Dimensional Row (DIN 6334)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e (mm) | Length l (mm) | Reference standard |
|---|---|---|---|---|---|
| M18 | 2.5 | 27 | 29.56 | 54 | DIN 6334 |
Spanner & Drive for M18 Hexagon Coupling Nuts
Drive geometry for M18 Hexagon Coupling Nuts is given by the row above; match the tool to the listed values.
Tightening Torque for M18
| Class 8.8 (dry, ~µ 0.125) | ≈ 290 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 405 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 485 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 M18
| Tensile stress area As (ISO 898-1) | 192 mm² |
|---|---|
| Proof load, class 8.8 | 115 kN |
| Proof load, class 10.9 | 159 kN |
| Proof load, class 12.9 | 186 kN |
| Min. ultimate tensile, class 8.8 | 154 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 M18 Hexagon Coupling Nuts
M18 Hexagon Coupling Nuts are commonly specified for structural joints, flange connections and heavy equipment foundations.
Installation Tips for M18 Hexagon Coupling Nuts
- At M18 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 M18
Pair M18 with the matching M18 bolt or screw, plus a M18 flat washer where required to distribute load on softer materials.
