Material specification page for self-drilling screws in Grade 12.9 Steel. Covers the grade designation (class 12.9), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to DIN 7504.
Why Choose Grade 12.9 Steel for Self-Drilling Screws
The highest common strength class, for high-load machine assembly. For self-drilling 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 |
Corrosion Behavior in Service
Carbon and alloy steel self-drilling screws 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 Self-Drilling 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 Self-Drilling Screws Available in Grade 12.9 Steel
| Size | Nominal diameter (mm) | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Drill point capacity (mm) | Common length range (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|---|
| ST3.5 | 3.5 | 1.27 | 6.9 | 2.1 | 0.7~2.0 | 13~25 | DIN 7504 K/N | Tek self-drilling screw, drill flute point |
| ST3.9 | 3.9 | 1.29 | 7.5 | 2.3 | 0.7~2.5 | 13~32 | DIN 7504 K/N | Tek self-drilling screw, drill flute point |
| ST4.2 | 4.2 | 1.41 | 8.2 | 2.5 | 0.7~3.0 | 13~38 | DIN 7504 K/N | Tek self-drilling screw, drill flute point |
| ST4.8 | 4.8 | 1.59 | 9.5 | 2.9 | 0.7~4.0 | 16~50 | DIN 7504 K/N | Tek self-drilling screw, drill flute point |
| ST5.5 | 5.5 | 1.81 | 10.9 | 3.3 | 1.0~5.0 | 19~60 | DIN 7504 K/N | Tek self-drilling screw, drill flute point |
| ST6.3 | 6.3 | 1.81 | 12.5 | 3.8 | 1.0~6.0 | 19~80 | DIN 7504 K/N | Tek self-drilling screw, drill flute point |