Specifying Self-Tapping Screws in A2 Stainless Steel pairs the dimensional form of Self-Tapping Screws (DIN 7976 / ISO 1481) with the engineering properties of A2 Stainless Steel. This page explains when to choose the grade, how it behaves in service, and which grades to compare it against.
Why Choose A2 Stainless Steel for Self-Tapping Screws
The most common stainless grade for indoor and general outdoor fasteners. For self-tapping screws, this matters when good general corrosion resistance is the primary requirement.
Mechanical & Physical Properties
| Grade designation | A2-70 (304) |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C |
| Corrosion characteristic | Good general corrosion resistance |
Corrosion Behavior in Service
A2 (304) gives excellent atmospheric and most-water corrosion resistance and is the most common stainless for Self-Tapping Screws in indoor and general outdoor service. In chloride-bearing environments (marine air, road salt, swimming pools) consider stepping up to A4 (316).
Galvanic & Galling Considerations
Two important notes for stainless self-tapping screws: (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.
Sizes of Self-Tapping Screws Available in A2 Stainless 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 |