Grade 12.9 Steel Countersunk Socket Screws combine the dimensional form of ISO 10642 / DIN 7991 with the material properties of grade class 12.9: requires plating or black-oxide 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 12.9 Steel for Countersunk Socket Screws
The highest common strength class, for high-load machine assembly. For countersunk socket screws, 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 |
Galvanic & Galling Considerations
For countersunk socket screws 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 Countersunk Socket Screws, 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 Countersunk Socket Screws Available in Grade 12.9 Steel
| Size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Hex key s (mm) | Countersink angle (deg) | Reference standard |
|---|---|---|---|---|---|---|
| M3 | 0.5 | 6.72 | 1.86 | 2.0 | 90 | ISO 10642 / DIN 7991 |
| M4 | 0.7 | 8.96 | 2.48 | 2.5 | 90 | ISO 10642 / DIN 7991 |
| M5 | 0.8 | 11.2 | 3.1 | 3.0 | 90 | ISO 10642 / DIN 7991 |
| M6 | 1.0 | 13.44 | 3.72 | 4.0 | 90 | ISO 10642 / DIN 7991 |
| M8 | 1.25 | 17.92 | 4.96 | 5.0 | 90 | ISO 10642 / DIN 7991 |
| M10 | 1.5 | 22.4 | 6.2 | 6.0 | 90 | ISO 10642 / DIN 7991 |
| M12 | 1.75 | 26.88 | 7.44 | 8.0 | 90 | ISO 10642 / DIN 7991 |
| M14 | 2.0 | 30.0 | 8.4 | 10.0 | 90 | ISO 10642 / DIN 7991 |
| M16 | 2.0 | 33.6 | 9.3 | 10.0 | 90 | ISO 10642 / DIN 7991 |
| M20 | 2.5 | 40.32 | 11.2 | 12.0 | 90 | ISO 10642 / DIN 7991 |
| M24 | 3.0 | 47.04 | 13.0 | 14.0 | 90 | ISO 10642 / DIN 7991 |