When Lag Screws (Hex Wood Screws) are required in Grade 8.8 Steel, the alternative grades and the trade-offs between them matter as much as the dimensions. This page covers both, plus mechanical and corrosion data.
Why Choose Grade 8.8 Steel for Lag Screws (Hex Wood Screws)
The workhorse medium-carbon alloy grade for structural joints. For lag screws (hex wood screws), 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 |
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 8.8 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 |