Property Class 12.9 Steel Sealing Cap Nuts are supplied to DIN 1587. The grade provides requires plating or black-oxide protection and is magnetic; the practical service range is commonly limited to approx. +300 °C; confirm against the coating and the load. Property data, grade comparison and the full size table follow.
Why Choose Property Class 12.9 Steel for Sealing Cap Nuts
The highest common strength class, for high-load machine assembly. For sealing cap 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 sealing cap 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 sealing cap 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 Sealing Cap Nuts Available in Property Class 12.9 Steel
| Thread size | Pitch (mm) | Across flats s (mm) | Across corners e (mm) | Total height m (mm) | Dome diameter (mm) | O-ring seat | Reference standard |
|---|---|---|---|---|---|---|---|
| M5 | 0.8 | 8 | 8.79 | 10 | 8 | 4.5 x 1.5 NBR | DIN 1587 + O-ring |
| M6 | 1.0 | 10 | 11.05 | 12 | 10 | 5.5 x 1.5 NBR | DIN 1587 + O-ring |
| M8 | 1.25 | 13 | 14.38 | 15 | 13 | 7.5 x 2.0 NBR | DIN 1587 + O-ring |
| M10 | 1.5 | 17 | 18.90 | 18 | 17 | 9.5 x 2.0 NBR | DIN 1587 + O-ring |
| M12 | 1.75 | 19 | 21.10 | 22 | 19 | 11.5 x 2.0 NBR | DIN 1587 + O-ring |
| M16 | 2.0 | 24 | 26.75 | 28 | 24 | 15.5 x 2.5 NBR | DIN 1587 + O-ring |
