For cap (acorn) nuts in A2 Stainless Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for A2 Stainless Steel (A2-70 (304)) is summarized below together with every size supplied.
Why Choose A2 Stainless Steel for Cap (Acorn) Nuts
The most common stainless grade for indoor and general outdoor fasteners. For cap (acorn) nuts, 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 Cap (Acorn) Nuts 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 cap (acorn) nuts: (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 Cap (Acorn) Nuts Available in A2 Stainless Steel
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Total height m (mm) | Dome diameter (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|
| M4 | 0.7 | 7.0 | 7.66 | 8.0 | 7.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M5 | 0.8 | 8.0 | 8.79 | 10.0 | 8.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M6 | 1.0 | 10.0 | 11.05 | 12.0 | 10.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M8 | 1.25 | 13.0 | 14.38 | 15.0 | 13.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M10 | 1.5 | 17.0 | 18.90 | 18.0 | 17.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M12 | 1.75 | 19.0 | 21.10 | 22.0 | 19.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M16 | 2.0 | 24.0 | 26.75 | 28.0 | 24.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |
| M20 | 2.5 | 30.0 | 33.53 | 34.0 | 30.0 | DIN 1587 | Closed-end domed cap nut, decorative / protective |