Grade 12.9 Steel Lag Screws (Hex Wood Screws) are stocked to DIN 571. The grade provides requires plating or black-oxide protection and is magnetic; the practical service range is up to approx. +300 °C. Property data, grade comparison and the full size table follow.
Why Choose Grade 12.9 Steel for Lag Screws (Hex Wood Screws)
The highest common strength class, for high-load machine assembly. For lag screws (hex wood 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 lag screws (hex wood 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.
Galvanic & Galling Considerations
For lag screws (hex wood 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.
Sizes of Lag Screws (Hex Wood Screws) Available in Grade 12.9 Steel
| Nominal diameter (mm) | Pitch (mm) | Width across flats s (mm) | Head height k (mm) | Pilot/guide hole (mm) | Common length range (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|
| 5 | 2.0 | 8.0 | 3.5 | 3.0 | 25~100 | DIN 571 | Wood screw, self-tapping point |
| 6 | 2.5 | 10.0 | 4.0 | 4.0 | 30~150 | DIN 571 | Wood screw, self-tapping point |
| 8 | 3.0 | 13.0 | 5.5 | 5.0 | 40~200 | DIN 571 | Wood screw, self-tapping point |
| 10 | 3.5 | 16.0 | 6.5 | 7.0 | 50~250 | DIN 571 | Wood screw, self-tapping point |
| 12 | 4.0 | 18.0 | 7.5 | 8.5 | 60~300 | DIN 571 | Wood screw, self-tapping point |
| 14 | 4.0 | 21.0 | 9.0 | 10.0 | 60~300 | DIN 571 | Wood screw, self-tapping point |
| 16 | 4.5 | 24.0 | 10.0 | 11.5 | 80~300 | DIN 571 | Wood screw, self-tapping point |
| 18 | 5.0 | 27.0 | 11.5 | 13.0 | 80~300 | DIN 571 | Wood screw, self-tapping point |
| 20 | 5.0 | 30.0 | 12.5 | 14.5 | 100~300 | DIN 571 | Wood screw, self-tapping point |
| 22 | 5.5 | 32.0 | 14.0 | 16.0 | 100~300 | DIN 571 | Wood screw, self-tapping point |
| 24 | 6.0 | 36.0 | 15.0 | 17.5 | 100~300 | DIN 571 | Wood screw, self-tapping point |