For hex nuts in Grade 12.9 Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for Grade 12.9 Steel (class 12.9) is summarized below together with every size supplied.
Why Choose Grade 12.9 Steel for Hex Nuts
The highest common strength class, for high-load machine assembly. For hex nuts, this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | class 12.9 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | up to approx. +300 °C |
| Corrosion characteristic | Requires plating or black-oxide protection |
Corrosion Behavior in Service
Carbon and alloy steel hex nuts require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Galvanic & Galling Considerations
For hex nuts in steel, the dominant compatibility issue is hydrogen embrittlement at high property classes (10.9 and above) when electroplated. Plating must be followed by an appropriate baking treatment, or a non-electroplated finish (mechanical zinc, zinc flake) should be substituted.
Sizes of Hex Nuts Available in Grade 12.9 Steel
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Nut height m style 1 (mm) | Nut height m style 2 (mm) | Reference standard |
|---|---|---|---|---|---|---|
| M1 | 0.25 | 2.5 | 2.71 | 0.8 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M1.2 | 0.25 | 3.0 | 3.28 | 1.0 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M1.4 | 0.3 | 3.0 | 3.28 | 1.2 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M1.6 | 0.35 | 3.2 | 3.48 | 1.3 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M2 | 0.4 | 4.0 | 4.32 | 1.6 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M2.5 | 0.45 | 5.0 | 5.45 | 2.0 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M3 | 0.5 | 5.5 | 6.01 | 2.4 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M3.5 | 0.6 | 6.0 | 6.58 | 2.8 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M4 | 0.7 | 7.0 | 7.66 | 3.2 | - | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M5 | 0.8 | 8.0 | 8.79 | 4.0 | 5.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M6 | 1.0 | 10.0 | 11.05 | 5.0 | 6.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M8 | 1.25 | 13.0 | 14.38 | 6.5 | 8.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M10 | 1.5 | 16.0 | 17.77 | 8.0 | 10.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M12 | 1.75 | 18.0 | 20.03 | 10.0 | 12.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M14 | 2.0 | 21.0 | 23.36 | 11.0 | 14.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M16 | 2.0 | 24.0 | 26.75 | 13.0 | 16.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M18 | 2.5 | 27.0 | 29.56 | 15.0 | 18.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M20 | 2.5 | 30.0 | 32.95 | 16.0 | 20.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M22 | 2.5 | 32.0 | 35.03 | 18.0 | 22.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M24 | 3.0 | 36.0 | 39.55 | 19.0 | 24.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M27 | 3.0 | 41.0 | 45.2 | 22.0 | 27.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M30 | 3.5 | 46.0 | 50.85 | 24.0 | 30.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M33 | 3.5 | 50.0 | 55.37 | 26.0 | 33.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M36 | 4.0 | 55.0 | 60.79 | 29.0 | 36.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M39 | 4.0 | 60.0 | 66.44 | 31.0 | 39.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M42 | 4.5 | 65.0 | 71.3 | 34.0 | 42.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M45 | 4.5 | 70.0 | 76.95 | 36.0 | 45.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M48 | 5.0 | 75.0 | 82.6 | 38.0 | 48.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M52 | 5.0 | 80.0 | 88.25 | 42.0 | 52.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |
| M56 | 5.5 | 85.0 | 93.56 | 45.0 | 56.0 | ISO 4032 (Style1) / ISO 4033 (Style2) |