Specifying Self-Tapping Screws in Grade 8.8 Steel pairs the dimensional form of Self-Tapping Screws (DIN 7976 / ISO 1481) with the engineering properties of Grade 8.8 Steel. This page explains when to choose the grade, how it behaves in service, and which grades to compare it against.
Why Choose Grade 8.8 Steel for Self-Tapping Screws
The workhorse medium-carbon alloy grade for structural joints. For self-tapping 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 self-tapping 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-Tapping Screws, class 10.9 or 12.9 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-Tapping Screws Available in Grade 8.8 Steel
| Size | Nominal diameter (mm) | Pilot hole (mm) | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Plate thickness (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|---|
| ST2.2 | 2.2 | 1.7 | 0.71 | 4.2 | 1.4 | 0.5~1.0 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST2.9 | 2.9 | 2.3 | 0.94 | 5.6 | 1.7 | 0.6~1.6 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST3.5 | 3.5 | 2.8 | 1.27 | 6.9 | 2.1 | 0.8~2.0 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST3.9 | 3.9 | 3.1 | 1.29 | 7.5 | 2.3 | 0.9~2.5 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST4.2 | 4.2 | 3.4 | 1.41 | 8.2 | 2.5 | 1.0~2.5 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST4.8 | 4.8 | 3.9 | 1.59 | 9.5 | 2.9 | 1.2~3.0 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST5.5 | 5.5 | 4.5 | 1.81 | 10.9 | 3.3 | 1.5~3.5 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST6.3 | 6.3 | 5.1 | 1.81 | 12.5 | 3.8 | 2.0~4.0 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST8.0 | 8.0 | 6.7 | 2.12 | 16.0 | 4.8 | 2.5~5.0 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |
| ST9.5 | 9.5 | 8.0 | 2.12 | 19.0 | 5.7 | 3.0~6.0 | DIN 7976 / ISO 1481 | Cross-recess pan-head self-tapping |