Hexagon Coupling Nuts manufactured in Property Class 12.9 Steel (ISO 898-1 property class 12.9) are dimensioned to DIN 6334. 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 Property Class 12.9 Steel for Hexagon Coupling Nuts
The highest common strength class, for high-load machine assembly. For hexagon coupling nuts, this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 12.9 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
| Corrosion characteristic | Requires plating or black-oxide protection |
Corrosion Behavior in Service
Carbon and alloy steel hexagon coupling 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.
Comparable Grades
For Hexagon Coupling Nuts, 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 Hexagon Coupling Nuts Available in Property Class 12.9 Steel
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e (mm) | Length l (mm) | Reference standard |
|---|---|---|---|---|---|
| M6 | 1.0 | 10 | 11.05 | 18 | DIN 6334 |
| M8 | 1.25 | 13 | 14.38 | 24 | DIN 6334 |
| M10 | 1.5 | 17 | 18.90 | 30 | DIN 6334 |
| M12 | 1.75 | 19 | 21.10 | 36 | DIN 6334 |
| M14 | 2.0 | 22 | 24.49 | 42 | DIN 6334 |
| M16 | 2.0 | 24 | 26.75 | 48 | DIN 6334 |
| M18 | 2.5 | 27 | 29.56 | 54 | DIN 6334 |
| M20 | 2.5 | 30 | 33.53 | 60 | DIN 6334 |
| M22 | 2.5 | 32 | 35.03 | 66 | DIN 6334 |
| M24 | 3.0 | 36 | 39.98 | 72 | DIN 6334 |
| M27 | 3.0 | 41 | 45.20 | 81 | DIN 6334 |
| M30 | 3.5 | 46 | 50.85 | 90 | DIN 6334 |
| M33 | 3.5 | 50 | 55.37 | 99 | DIN 6334 |
| M36 | 4.0 | 55 | 60.79 | 108 | DIN 6334 |
