Material specification page for hexagon coupling nuts in Property Class 8.8 Steel. Covers the grade designation (ISO 898-1 property class 8.8), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to DIN 6334.
Why Choose Property Class 8.8 Steel for Hexagon Coupling Nuts
The workhorse medium-carbon alloy class for structural joints. For hexagon coupling nuts, this matters when requires plating (zinc) for corrosion protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 8.8 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
| Corrosion characteristic | Requires plating (zinc) for corrosion 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 10.9 or 12.9 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 8.8 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 |
