The M16 size of Hex Nut is dimensioned by GB/T 6170 / ISO 4032. The table below gives the dimensional row from the standard, followed by the drive and the installation notes for this type.
M16 Dimensional Row (GB/T 6170 / ISO 4032)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|---|
| M16 | 2.0 | 24.0 | 26.75 | 14.8 | ISO 4032 / GB/T 6170 |
Spanner & Drive for M16 Hex Nut — GB/T 6170 / ISO 4032 (Series 066)
M16 Hex Nut — GB/T 6170 / ISO 4032 (Series 066) have a width across flats of 24.0 mm — fit a 24.0 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.
Tightening Torque for M16
| Class 8.8 (dry, ~µ 0.125) | ≈ 210 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 295 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 355 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 M16
| Tensile stress area As (ISO 898-1) | 157 mm² |
|---|---|
| Proof load, class 8.8 | 91 kN |
| Proof load, class 10.9 | 130 kN |
| Proof load, class 12.9 | 152 kN |
| Min. ultimate tensile, class 8.8 | 126 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 M16 Hex Nut — GB/T 6170 / ISO 4032 (Series 066)
M16 Hex Nut — GB/T 6170 / ISO 4032 (Series 066) are commonly specified for medium-duty structural joints and motor / chassis mounting.
Installation Tips for M16 Hex Nut — GB/T 6170 / ISO 4032 (Series 066)
- 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 M16
When the joint preload approaches the proof load of M16 class 8.8, step up to M20 class 8.8 (or move to M16 class 10.9). When the joint is over-specified, M12 often saves weight and cost without losing the safety margin.
