Grade 8.8 Steel Cap (Acorn) Nuts combine the dimensional form of DIN 1587 with the material properties of grade class 8.8: requires plating (zinc) for corrosion protection, magnetic, service range up to approx. +300 °C. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.
Why Choose Grade 8.8 Steel for Cap (Acorn) Nuts
The workhorse medium-carbon alloy grade for structural joints. For cap (acorn) nuts, this matters when requires plating (zinc) for corrosion protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | class 8.8 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | up to approx. +300 °C |
| Corrosion characteristic | Requires plating (zinc) for corrosion protection |
Galvanic & Galling Considerations
For cap (acorn) 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.
Comparable Grades
For Cap (Acorn) 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 Cap (Acorn) Nuts Available in Grade 8.8 Steel
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Total height m (mm) | Dome diameter (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|
| M4 | 0.7 | 7.0 | 7.66 | 8.0 | 7.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M5 | 0.8 | 8.0 | 8.79 | 10.0 | 8.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M6 | 1.0 | 10.0 | 11.05 | 12.0 | 10.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M8 | 1.25 | 13.0 | 14.38 | 15.0 | 13.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M10 | 1.5 | 17.0 | 18.90 | 18.0 | 17.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M12 | 1.75 | 19.0 | 21.10 | 22.0 | 19.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M16 | 2.0 | 24.0 | 26.75 | 28.0 | 24.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M20 | 2.5 | 30.0 | 33.53 | 34.0 | 30.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |