For key-locking 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 Key-Locking Threaded Inserts
The most common stainless group for indoor and general outdoor fasteners. For key-locking 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 Key-Locking 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 key-locking 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
Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.
Sizes of Key-Locking Threaded Inserts Available in A2 Stainless Steel
| Internal thread | External thread | Length L (mm) | Tapped hole required | Keys | Locking method | Material | Typical use |
|---|---|---|---|---|---|---|---|
| M4 | M8x1.0 | 8.0 | M8x1.0 | 4 | Driven keys broach parent | Carbon steel / 303 stainless | High-vibration repair |
| M5 | M10x1.25 | 10.0 | M10x1.25 | 4 | Driven keys broach parent | Carbon steel / 303 stainless | High-vibration repair |
| M6 | M12x1.25 | 12.0 | M12x1.25 | 4 | Driven keys broach parent | Carbon steel / 303 stainless | High-vibration repair |
| M8 | M14x1.25 | 14.0 | M14x1.25 | 4 | Driven keys broach parent | Carbon steel / 303 stainless | Aerospace, motorsport |
| M10 | M16x1.5 | 16.0 | M16x1.5 | 4 | Driven keys broach parent | Carbon steel / 303 stainless | Aerospace, motorsport |
| M12 | M20x1.5 | 20.0 | M20x1.5 | 4 | Driven keys broach parent | Carbon steel / 303 stainless | Aerospace, motorsport |
