When Self-Drilling Screws are required in A4 Stainless 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 A4 Stainless Steel for Self-Drilling Screws
Specified for marine, coastal and chemical applications. For self-drilling screws, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | A4-80 (316) |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Self-Drilling Screws in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
Two important notes for stainless self-drilling 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-Drilling Screws Available in A4 Stainless 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 |