A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70) is the most common stainless group for indoor and general outdoor fasteners. When thread cutting screws (type f) are specified in this grade, the dimensions remain per DIN 7516; the material determines corrosion behavior (good general corrosion resistance) and the service temperature range (approx. -200 °C to +400 °C, subject to the property class and the joint). Both are covered below with the size table.
Why Choose A2 Stainless Steel for Thread Cutting Screws (Type F)
The most common stainless group for indoor and general outdoor fasteners. For thread cutting screws (type f), this matters when good general corrosion resistance is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Good general corrosion resistance |
Galvanic & Galling Considerations
Two important notes for stainless thread cutting screws (type f): (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.
Comparable Grades
For Thread Cutting Screws (Type F), the alternative stainless grade is A4 (316). A2 (304) suits general indoor and outdoor service; A4 (316) adds molybdenum for marine and chloride environments. Where higher strength matters more than corrosion, switch to plated alloy-steel class 8.8 or 10.9.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so in the presence of an electrolyte — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. The effect is driven by the area ratio: a small stainless fastener in a large aluminum section is normally acceptable, while a large stainless fastener in thin aluminum is not. Where the joint is wet, isolate the two metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Thread Cutting Screws (Type F) Available in A2 Stainless Steel
| Thread size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Core hole in steel (mm) | Max material thickness (mm) | Common length range (mm) | Reference standard |
|---|---|---|---|---|---|---|---|
| M3 | 0.5 | 5.6 | 2.4 | 2.65 | 3 | 6~25 | DIN 7516 |
| M4 | 0.7 | 8.0 | 3.1 | 3.55 | 4 | 8~30 | DIN 7516 |
| M5 | 0.8 | 9.5 | 3.7 | 4.50 | 5 | 8~40 | DIN 7516 |
| M6 | 1.0 | 12.0 | 4.6 | 5.40 | 6 | 10~50 | DIN 7516 |
| M8 | 1.25 | 16.0 | 6.0 | 7.20 | 8 | 12~50 | DIN 7516 |
| M10 | 1.5 | 20.0 | 7.5 | 9.00 | 10 | 16~60 | DIN 7516 |
