M12 Hex Nut, Fine Pitch are manufactured to GB/T 6171 / ISO 8673. This page lists the controlling dimensions for the M12 size together with the drive and the installation notes for this type.
M12 Dimensional Row (GB/T 6171 / ISO 8673)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|---|
| M12 | 1.75 | 18.0 | 20.03 | 10.8 | ISO 4032 / GB/T 6170 |
Spanner & Drive for M12 Hex Nut, Fine Pitch — GB/T 6171 / ISO 8673 (Series 067)
M12 Hex Nut, Fine Pitch — GB/T 6171 / ISO 8673 (Series 067) 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.
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.
Common Applications for M12 Hex Nut, Fine Pitch — GB/T 6171 / ISO 8673 (Series 067)
M12 Hex Nut, Fine Pitch — GB/T 6171 / ISO 8673 (Series 067) are commonly specified for medium-duty structural joints and motor / chassis mounting.
Mating Parts for M12
Pair M12 with the matching M12 bolt or screw, plus a M12 flat washer where required to distribute load on softer materials.
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.
