For dowel screws (wood-to-metal) in A4 Stainless Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) is summarized below together with every size supplied.
Why Choose A4 Stainless Steel for Dowel Screws (Wood-to-Metal)
Specified for marine, coastal and chemical applications. For dowel screws (wood-to-metal), this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Dowel Screws (Wood-to-Metal) in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
Two important notes for stainless dowel screws (wood-to-metal): (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 Dowel Screws (Wood-to-Metal) Available in A4 Stainless Steel
| Machine thread | Wood end nominal (mm) | Overall length (mm) | Wood end length (mm) | Machine end length (mm) | Pilot hole in hardwood (mm) | Material |
|---|---|---|---|---|---|---|
| M5 | 5.0 | 40 | 20 | 16 | 3.2 | Steel zinc plated |
| M6 | 6.0 | 50 | 25 | 20 | 4.0 | Steel zinc plated |
| M6 | 6.0 | 60 | 30 | 25 | 4.0 | Steel zinc plated |
| M8 | 8.0 | 70 | 35 | 30 | 5.5 | Steel zinc plated |
| M8 | 8.0 | 80 | 40 | 35 | 5.5 | Steel zinc plated |
| M10 | 10.0 | 100 | 50 | 45 | 7.0 | Steel zinc plated |
