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 hex standoffs, female-female are specified in this grade, the dimensions remain per Industry standard; 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 Hex Standoffs, Female-Female
The most common stainless group for indoor and general outdoor fasteners. For hex standoffs, female-female, 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 hex standoffs, female-female: (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 Hex Standoffs, Female-Female, 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 Hex Standoffs, Female-Female Available in A2 Stainless Steel
| Thread size | Pitch (mm) | Across flats s (mm) | Across corners e (mm) | Length range L (mm) | Thread depth each end (mm) | Reference standard |
|---|---|---|---|---|---|---|
| M2.5 | 0.45 | 5 | 5.8 | 5~40 | 5 | Industry standard |
| M3 | 0.5 | 5.5 | 6.4 | 5~50 | 6 | Industry standard |
| M4 | 0.7 | 7 | 8.1 | 6~60 | 8 | Industry standard |
| M5 | 0.8 | 8 | 9.2 | 8~80 | 10 | Industry standard |
| M6 | 1.0 | 10 | 11.5 | 10~100 | 12 | Industry standard |
| M8 | 1.25 | 13 | 15.0 | 12~100 | 16 | Industry standard |
| M10 | 1.5 | 17 | 19.6 | 15~100 | 20 | Industry standard |
