Home » Hex Head Wood Screws (DIN 571) - Marine Stainless Steel (A4)

Hex Head Wood Screws (DIN 571) - Marine Stainless Steel (A4)

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Hex Head Wood Screws — DIN 571

Marine Stainless Steel A4 (SUS316) · Grade A4-70 · Passivated Finish

DIN 571ISO 3506-1A4-70SUS316 / 1.4401RoHS Compliant

Premium marine-grade hex head lag screws conforming to DIN 571 standard. Manufactured in A4 stainless steel (SUS316 / 1.4401) with molybdenum content for superior resistance to chloride corrosion, saltwater, and aggressive chemical environments. The preferred choice for marine construction, coastal infrastructure, and demanding industrial applications.

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DIN 571 · A4 Marine Stainless Steel
⚓ Why A4 Marine Grade? Unlike standard A2 (SUS304), A4 stainless steel contains 2–3% molybdenum (Mo), which dramatically improves resistance to pitting and crevice corrosion in chloride-rich environments such as seawater, de-icing salts, and industrial chemicals. A4-70 is the recommended grade for all marine, coastal, and chemically aggressive applications.

Key Features

⚓

Marine Grade A4 (SUS316)

Contains 2–3% molybdenum for superior chloride and saltwater corrosion resistance.

📐

DIN 571 Standard

Fully compliant with DIN 571 hex head wood screw dimensional standard.

⚡

Grade A4-70

Minimum tensile strength 700 MPa per ISO 3506-1.

✨

Passivated Surface

Clean passivation finish — no coating, maintains natural stainless appearance and maximum corrosion resistance.

🔧

External Hex Drive

WS8 to WS24 hex drive for high-torque installation with standard metric wrenches.

📏

Wide Size Range

M5 to M16, lengths from 20 mm to 300 mm. Custom lengths available on request.

Dimensional Specifications — DIN 571

All dimensions conform to DIN 571 standard. Tolerances per ISO 4759-1.

Nominal Diameter (d) Thread Pitch (p) Head Height (k) Head Width A/F (s) Wrench Size Min. Length Max. Length Point Type
M5 2.0 mm 3.5 mm 8 mm WS8 20 mm 60 mm Gimlet Point
M6 2.5 mm 4.0 mm 10 mm WS10 20 mm 140 mm Gimlet Point
M8 3.0 mm 5.5 mm 13 mm WS13 25 mm 200 mm Gimlet Point
M10 3.5 mm 7.0 mm 17 mm WS17 30 mm 200 mm Gimlet Point
M12 4.0 mm 8.0 mm 19 mm WS19 40 mm 250 mm Gimlet Point
M16 5.0 mm 10.0 mm 24 mm WS24 60 mm 300 mm Gimlet Point

Available Sizes Matrix — A4 Marine Stainless Steel

✓ = Standard stock size  |  — = Available on request (MOQ applies)

Ø \ Length 20 25 30 35 40 45 50 55 60 65 70 75 80 90 100 110 120 130 140 150 160 180 200 220 250 300
M5 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ — — — — — — — — — — — — — — — — —
M6 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ — ✓ ✓ ✓ ✓ ✓ ✓ ✓ — — — — — — —
M8 — ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ — — — — — — — ✓ — — —
M10 — — ✓ ✓ ✓ ✓ ✓ — ✓ — ✓ — ✓ ✓ ✓ — ✓ — — ✓ — ✓ ✓ — — —
M12 — — — — ✓ — ✓ — ✓ — ✓ — ✓ ✓ ✓ — ✓ — — ✓ — ✓ ✓ — ✓ —
M16 — — — — — — — — ✓ — ✓ — ✓ ✓ ✓ — ✓ — — ✓ — ✓ ✓ — ✓ ✓

Mechanical Properties — A4-70 Grade

All values per ISO 3506-1. Test performed at room temperature.

Property Value Test Standard
Material Grade A4 (SUS316 / 1.4401) ISO 3506-1
Strength Grade A4-70 ISO 3506-1
Min. Tensile Strength 700 MPa ISO 3506-1
Min. Yield Strength (0.2% proof) 450 MPa ISO 3506-1
Min. Elongation 20% ISO 3506-1
Hardness (max) 250 HV ISO 3506-1
Surface Treatment Passivated ASTM A967 / ISO 16048
Magnetic Properties Slightly magnetic (work-hardened) —
Operating Temperature −200°C to +400°C —
Corrosion Resistance Excellent (C4/C5 / marine environment) ISO 12944
Pitting Resistance (PRE) ≥ 24 (Mo-enhanced) ASTM G48

Chemical Composition — SUS316 / 1.4401 (A4 Marine Stainless Steel)

Element Min % Max % Role
Chromium (Cr) 16.5 18.5 Primary corrosion resistance
Nickel (Ni) 10.0 13.0 Austenitic structure stability
Molybdenum (Mo) 2.0 2.5 Chloride / pitting resistance ★
Carbon (C) — 0.07 Strength control
Manganese (Mn) — 2.0 Deoxidizer
Silicon (Si) — 1.0 Deoxidizer
Phosphorus (P) — 0.045 —
Sulfur (S) — 0.015 —
Nitrogen (N) — 0.11 Strength enhancement
Iron (Fe) Balance — Base metal

A4 vs A2 — Which Grade Do You Need?

⚓ A4 (SUS316) — This Product

  • Contains 2–3% Molybdenum (Mo)
  • Superior chloride & saltwater resistance
  • Recommended for marine & coastal use
  • Suitable for C4/C5 corrosion categories
  • Ideal for food, pharma, chemical industries
  • Higher cost, maximum protection

🔩 A2 (SUS304) — Standard Grade

  • No Molybdenum content
  • Good general corrosion resistance
  • Suitable for indoor & mild outdoor use
  • C3/C4 corrosion categories
  • Not recommended for saltwater exposure
  • Lower cost, wide availability

Pre-Drilling Recommendations

Pre-drilling is mandatory for hardwoods and strongly recommended for softwoods. Pilot hole depth ≥ 2/3 of screw length.

Screw Diameter Softwood — Pilot Hole Hardwood — Pilot Hole Clearance Hole
M5 3.0 mm 3.5 mm 5.5 mm
M6 3.5 mm 4.5 mm 6.5 mm
M8 5.0 mm 6.0 mm 9.0 mm
M10 6.0 mm 7.5 mm 11.0 mm
M12 7.0 mm 9.0 mm 13.0 mm
M16 10.0 mm 12.0 mm 17.0 mm

Recommended Tightening Torque (Reference Values)

Screw Size Softwood (N·m) Hardwood (N·m) Notes
M5 × 40 3 – 5 4 – 6 Use torque wrench
M6 × 50 6 – 9 8 – 12 —
M8 × 70 15 – 20 18 – 25 —
M10 × 100 30 – 40 35 – 50 —
M12 × 120 55 – 70 65 – 85 —
M16 × 150 120 – 150 140 – 180 —

Typical Applications

⛵

Marine & Boat Building

Deck fittings, dock structures, boat building — where saltwater exposure demands maximum corrosion protection.

🌊

Coastal & Offshore Infrastructure

Boardwalks, piers, jetties, and coastal timber structures in salt-air environments.

🏊

Swimming Pools & Aquatic Facilities

Chlorinated water environments where standard stainless steel is prone to pitting corrosion.

🏭

Chemical & Process Industries

Securing wooden structures in chemical plants, processing facilities, and aggressive industrial environments.

🍽️

Food & Beverage Processing

Hygienic, non-contaminating fasteners compliant with food-grade facility requirements.

❄️

Cold Storage & Refrigeration

Excellent performance at low temperatures down to −200°C for cold chain infrastructure.

Packaging & Ordering Information

📦 Standard Packaging

  • M5–M6: 100 / 200 / 500 / 1,000 pcs per box
  • M8–M10: 50 / 100 / 200 pcs per box
  • M12–M16: 10 / 25 / 50 pcs per box
  • Bulk / pallet quantities available on request
  • Custom packaging with FULLERKREG branding available

📋 Ordering Notes

  • MOQ: 1 box (standard sizes)
  • Custom lengths: MOQ 500 pcs, lead time 15–25 days
  • EN 10204 3.1 material certificates available on request
  • RoHS & REACH compliant
  • Country of Origin: China (full traceability)
  • OEM / private label orders welcome

Standards Compliance & Certifications

📐
DIN 571Hex Head Wood Screws dimensional standard
🔬
ISO 3506-1Mechanical properties of stainless steel fasteners
✅
ISO 9001:2015Quality management system certified
🌿
RoHS DirectiveRestriction of hazardous substances compliant
📄
EN 10204 3.1Material test certificate available on request
🇪🇺
REACH RegulationFully compliant

Frequently Asked Questions

Q1: Why choose A4 marine stainless steel over A2 for wood screws?
A4 (SUS316) contains 2–3% molybdenum, which significantly enhances resistance to pitting and crevice corrosion caused by chlorides (saltwater, de-icing salts, pool chemicals). A2 (SUS304) lacks molybdenum and can suffer pitting corrosion in marine or chloride-rich environments. For any coastal, marine, or chemically aggressive application, A4 is the correct choice.
Q2: What does A4-70 strength grade mean?
A4-70 designates the material (A4 = austenitic stainless steel with molybdenum) and the strength class (70 = minimum tensile strength of 700 MPa). This is defined by ISO 3506-1 and ensures the fastener meets both corrosion resistance and mechanical performance requirements.
Q3: Do DIN 571 A4 wood screws require pre-drilling?
Yes. Pre-drilling is strongly recommended for all wood types and mandatory for hardwoods. This prevents wood splitting, reduces installation torque, and ensures proper thread engagement. Refer to our pre-drilling table for recommended pilot hole sizes.
Q4: Are material test certificates available for A4 screws?
Yes. EN 10204 3.1 material test certificates confirming chemical composition and mechanical properties are available upon request for all orders. Please specify when placing your order.
Q5: Is A4 stainless steel suitable for swimming pool environments?
Yes. A4 (SUS316) is specifically recommended for chlorinated water environments such as swimming pools, water treatment facilities, and aquatic centers. The molybdenum content provides the necessary resistance to chloride-induced pitting corrosion that would affect A2 grade fasteners.
Q6: Can FULLERKREG supply custom lengths for A4 DIN 571 screws?
Yes. Custom lengths outside the standard range are available with a minimum order quantity of 500 pieces. Lead time is typically 15–25 business days. Contact our sales team with your specifications for a quotation.
Q7: What is the difference between SUS316 and SUS316L?
SUS316L (1.4404) is a low-carbon variant of SUS316 (1.4401), with carbon content ≤ 0.03% vs ≤ 0.07% for standard 316. The lower carbon in 316L reduces the risk of sensitization during welding. For fastener applications (non-welded), standard SUS316 / A4 provides equivalent corrosion resistance and is the standard grade for DIN 571 screws.
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