Stainless Steel Self-Tapping Screws A2 / A4
When the fastener must outlast the structure around it, the stainless self-tapping screw is the answer. A2 (304) and A4 (316) austenitic stainless steel gives bright, rust-free fastening for outdoor, marine and hygienic environments, while the sharp self-tapping thread forms its own thread in metal and plastic without pre-drilling. Supplied by a stainless fastener manufacturer across the full metric range.
Features and Benefits
- A2 / A4 stainless steel — no coating to scratch away, corrosion resistance is in the metal itself
- A4 (316) adds molybdenum for chloride-rich marine and chemical atmospheres
- Sharp self-tapping point with coarse thread — quick installation into steel, aluminum and plastics
- Bright passivated finish that stays clean in wash-down and exposed applications
- Head styles from pan and countersunk to hex washer, with Phillips or Torx drives
Typical Applications
- Outdoor structures, balustrades and street furniture
- Marine, waterfront and pool environments (A4 / 316)
- Food processing, brewing and pharmaceutical wash-down areas (A4 / 316)
- Signage, cladding and architectural panels
- Aluminum and stainless assembly where galvanic corrosion must be avoided
Model Specifications
| Size | Length Range | Head Styles | Material |
|---|---|---|---|
| 3.5 mm (#6) | 13-50 mm | Pan / countersunk / hex | A2 (304) / A4 (316) |
| 4.2 mm (#8) | 13-75 mm | Pan / countersunk / hex | A2 (304) / A4 (316) |
| 4.8 mm (#10) | 16-100 mm | Pan / countersunk / hex | A2 (304) / A4 (316) |
| 5.5 mm (#12) | 20-150 mm | Hex washer / countersunk | A2 (304) / A4 (316) |
| 6.3 mm (#14) | 25-200 mm | Hex washer | A2 (304) / A4 (316) |
A2 vs A4 Selection Guide
| Property | A2 (AISI 304) | A4 (AISI 316) |
|---|---|---|
| Molybdenum content | — | 2-3%, added chloride resistance |
| Best environment | General outdoor, urban | Marine, coastal, chemical |
| Typical corrosion rate vs carbon steel | Roughly 1/150 | Lower still in salt spray |
| Relative cost | Standard | Premium |
Material and Performance
- Material: A2 / A4 austenitic stainless to ISO 3506, mechanical class 70
- Thread: self-tapping, coarse pitch for metal and engineering plastics
- Finish: passivated bright; black oxide and lubricated versions for stainless threading into stainless
- Certification: material certificates to EN 10204 3.1 on request
Installation Guidelines
- Use sharp, matched driver bits — worn bits cam out and damage the recess on stainless heads.
- Where stainless screws thread into stainless nuts or holes, use an anti-galling lubricant.
- On hard metals, a pilot hole of 80-90% of root diameter improves thread life and drive speed.
- Avoid mixing with plain carbon fasteners in the same assembly — the carbon part will corrode preferentially.
- For wash-down areas, specify A4 and round heads without crevices that trap residue.
Why Source from BuildFastener
Full A2 and A4 programs from one supplier, from 3.5 mm to 6.3 mm with matching washers and nuts. Lots carry mill certificates and passivation verification. Contact us for wholesale pricing and marine-project packages.
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