For self-tapping threaded inserts in A2 Stainless Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70) is summarized below together with every size supplied.
Why Choose A2 Stainless Steel for Self-Tapping Threaded Inserts
The most common stainless group for indoor and general outdoor fasteners. For self-tapping threaded inserts, 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 |
Corrosion Behavior in Service
A2 (304) gives excellent atmospheric and most-water corrosion resistance and is the most common stainless for Self-Tapping Threaded Inserts 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 threaded inserts: (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.
Using Stainless Fasteners in Aluminum
The galvanic couple here runs the wrong way: aluminum is the less noble metal, so it corrodes and the fastener does not. What governs the rate is the ratio of areas — a large anode and a small cathode is a tolerable combination, the reverse concentrates the attack into thin material around the hole. An isolating washer plus sealant breaks the circuit; where that is impractical, match the fastener to the substrate.
Sizes of Self-Tapping Threaded Inserts Available in A2 Stainless Steel
| Internal thread | Outer diameter (mm) | Length L (mm) | Hole in parent (mm) | Suitable parent material | Head form | Material | Installation |
|---|---|---|---|---|---|---|---|
| M3 | 6.0 | 6.0 | 6.0 | Alloy, cast iron, plastic | Flush | Case-hardened steel | Mandrel or driver |
| M4 | 8.0 | 8.0 | 8.0 | Alloy, cast iron, plastic | Flush | Case-hardened steel | Mandrel or driver |
| M5 | 9.0 | 10.0 | 9.0 | Alloy, cast iron, plastic | Flush | Case-hardened steel | Mandrel or driver |
| M6 | 11.0 | 12.0 | 11.0 | Alloy, cast iron, plastic | Flush | Case-hardened steel | Mandrel or driver |
| M8 | 14.0 | 14.0 | 14.0 | Alloy, cast iron, timber | Flush | Case-hardened steel | Mandrel or driver |
| M10 | 16.0 | 18.0 | 16.0 | Alloy, cast iron, timber | Flush | Case-hardened steel | Mandrel or driver |
