Hex Nut manufactured in Grade 12.9 Steel (class 12.9) are dimensioned to GB/T 6170 / ISO 4032. The sections below give the mechanical and physical properties of the grade, its behavior in corrosive and elevated-temperature service, and the full size table.
Why Choose Grade 12.9 Steel for Hex Nut — GB/T 6170 / ISO 4032 (Series 066)
The highest common strength class, for high-load machine assembly. For hex nut — gb/t 6170 / iso 4032 (series 066), 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 nut — gb/t 6170 / iso 4032 (series 066) 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.
Comparable Grades
For Hex Nut — GB/T 6170 / ISO 4032 (Series 066), class 8.8 is the comparable strength step. Move up when the joint preload approaches the proof load of the current class; move down when the joint is over-specified. For corrosion-critical service, switch to stainless A2 or A4.
Sizes of Hex Nut — GB/T 6170 / ISO 4032 (Series 066) Available in Grade 12.9 Steel
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|---|
| M3 | 0.5 | 5.5 | 6.01 | 2.4 | ISO 4032 / GB/T 6170 |
| M4 | 0.7 | 7.0 | 7.66 | 3.2 | ISO 4032 / GB/T 6170 |
| M5 | 0.8 | 8.0 | 8.79 | 4.7 | ISO 4032 / GB/T 6170 |
| M6 | 1.0 | 10.0 | 11.05 | 5.2 | ISO 4032 / GB/T 6170 |
| M8 | 1.25 | 13.0 | 14.38 | 6.8 | ISO 4032 / GB/T 6170 |
| M10 | 1.5 | 16.0 | 17.77 | 8.4 | ISO 4032 / GB/T 6170 |
| M12 | 1.75 | 18.0 | 20.03 | 10.8 | ISO 4032 / GB/T 6170 |
| M14 | 2.0 | 21.0 | 23.36 | 12.8 | ISO 4032 / GB/T 6170 |
| M16 | 2.0 | 24.0 | 26.75 | 14.8 | ISO 4032 / GB/T 6170 |
| M18 | 2.5 | 27.0 | 30.14 | 15.8 | ISO 4032 / GB/T 6170 |
| M20 | 2.5 | 30.0 | 33.53 | 18.0 | ISO 4032 / GB/T 6170 |
| M24 | 3.0 | 36.0 | 39.98 | 21.5 | ISO 4032 / GB/T 6170 |
| M30 | 3.5 | 46.0 | 50.85 | 25.6 | ISO 4032 / GB/T 6170 |
| M36 | 4.0 | 55.0 | 60.79 | 31.0 | ISO 4032 / GB/T 6170 |