Home » DIN 916 / ISO 4029 Socket Set Screw Cup Point A2 Stainless

DIN 916 / ISO 4029 Socket Set Screw Cup Point A2 Stainless

DIN 916 / ISO 4029 — Socket Set Screw with Cup Point | A2 Stainless Steel

Brand: FULLERKREG  |  Material: A2 Stainless Steel (SUS304)  |  Surface: Passivated (Bright Finish)

Product Overview

FULLERKREG DIN 916 / ISO 4029 Socket Set Screws with Cup Point in A2 Stainless Steel (SUS304) are precision headless set screws engineered for corrosion-sensitive environments where alloy steel is unsuitable. The cup point geometry — a concave spherical recess at the tip — bites into the mating shaft surface to deliver reliable clamping, anti-rotation, and positioning performance. Combined with the inherent corrosion resistance of A2 stainless steel and a bright passivated finish, these set screws are the preferred choice for food processing, marine, pharmaceutical, chemical, and outdoor industrial applications.

Standards & Specifications

  • Standards: DIN 916, ISO 4029
  • Thread Form: ISO Metric Coarse Thread (per ISO 68-1)
  • Thread Tolerance: 6g (per ISO 965-1)
  • Drive Type: Hexagon Socket (Allen / Hex Key)
  • Point Type: Cup Point — concave spherical recess at tip
  • Material: A2 Stainless Steel (SUS304 / 1.4301 / 18-8)
  • Material Grade: A2 per ISO 3506-3
  • Surface Treatment: Passivated — bright, clean finish with enhanced corrosion resistance
  • Applicable Standard for Mechanical Properties: ISO 3506-3

Material & Mechanical Properties

Property Value Standard
Material A2 Stainless Steel (SUS304 / 1.4301) ISO 3506-3
Chemical Composition (Cr) 17.5 – 19.5% —
Chemical Composition (Ni) 8.0 – 10.5% —
Minimum Tensile Strength 700 MPa (A2-70) ISO 3506-3
Hardness (typical) HV 200 – 300 ISO 3506-3
Thread Tolerance 6g ISO 965-1
Surface Treatment Passivated (Bright / 洗白钝化) —
Magnetic Properties Slightly magnetic (work-hardened) —
Operating Temperature -196°C to +800°C (intermittent) —

Note: A2 stainless steel set screws are not hardened to the same level as alloy steel 45H/12.9 grade. For applications requiring maximum holding force on hardened shafts, alloy steel grade is recommended. A2 is optimized for corrosion resistance.

Surface Treatment: Passivation (洗白钝化)

All FULLERKREG A2 stainless set screws undergo a passivation treatment after manufacturing:

  • Process: Acid passivation (citric acid or nitric acid bath) removes free iron and surface contaminants from the machined surface.
  • Result: A bright, clean, silver-white finish with a reinforced chromium oxide passive layer.
  • Benefit: Significantly enhances corrosion resistance beyond the as-machined state, especially in chloride-containing environments.
  • Appearance: Uniform bright metallic finish — no discoloration, no scale, no heat tint.

Dimensional Range

Thread Size Pitch (mm) Socket Size s (mm) Length Range (mm)
M3 0.5 1.5 3 – 16
M4 0.7 2.0 4 – 20
M5 0.8 2.5 5 – 25
M6 1.0 3.0 6 – 30
M8 1.25 4.0 8 – 40
M10 1.5 5.0 10 – 50
M12 1.75 6.0 12 – 60
M16 2.0 8.0 16 – 80
M20 2.5 10.0 20 – 100
M24 3.0 12.0 25 – 120

Custom lengths and special configurations available upon request. Contact FULLERKREG for non-standard requirements.

Cup Point Geometry

The cup point (concave spherical recess) is the defining feature of DIN 916 / ISO 4029 set screws. Key functional advantages:

  • Positive mechanical lock: The rim of the cup bites into the shaft surface, resisting rotation and axial movement.
  • Reduced shaft damage: The concave geometry distributes contact stress more evenly than cone or dog points, minimizing shaft marring.
  • Vibration resistance: Reliable performance under dynamic and cyclic loads.
  • Repositionable: Allows limited repositioning without severe shaft damage.
  • Versatile: Suitable for both hardened and unhardened shafts; ideal for stainless and non-ferrous shafts in corrosive environments.

Corrosion Resistance of A2 Stainless Steel

  • Excellent resistance to atmospheric corrosion, fresh water, mild acids, and alkalis.
  • Good resistance to food acids, dilute organic acids, and many chemical environments.
  • Moderate resistance to chloride environments — suitable for light marine exposure; for severe marine or seawater immersion, A4 (SUS316) is recommended.
  • Not recommended for strong reducing acids (e.g., hydrochloric acid) or high-chloride immersion without additional protection.
  • Passivation further enhances the natural chromium oxide passive layer, improving resistance to pitting and crevice corrosion.

Typical Applications

  • Food processing and beverage equipment (FDA-compatible environments)
  • Pharmaceutical and medical device manufacturing
  • Chemical processing equipment and laboratory instruments
  • Marine and coastal outdoor installations
  • Shaft-to-hub locking in corrosive or washdown environments
  • Pumps, valves, and fluid handling systems
  • Semiconductor and cleanroom equipment
  • Architectural and decorative hardware requiring a bright finish
  • General industrial machinery in humid or wet environments

A2 vs. Alloy Steel — Selection Guide

Property A2 Stainless (This Product) Alloy Steel 45H/12.9
Corrosion Resistance ✅ Excellent ⚠️ Limited (Black Oxide only)
Surface Hardness HV 200–300 (moderate) HRC 45–53 (very high)
Tensile Strength 700 MPa (A2-70) 1220 MPa (12.9)
Holding Force on Hard Shafts ⚠️ Moderate ✅ Maximum
Food / Pharma Suitability ✅ Yes ❌ Not recommended
Appearance Bright silver-white Matte black
Magnetic Slightly (work-hardened) Yes

Installation Guidelines

  • Use the correct hex key (Allen wrench) matching the socket size — refer to the dimensional table above.
  • Ensure the shaft and bore are clean and free of oil or debris before installation.
  • For vibration-critical applications, apply a stainless-compatible thread-locking compound (e.g., Loctite 243 or equivalent).
  • Anti-galling precaution: Stainless steel fasteners are susceptible to galling (cold welding) during installation. Apply anti-seize compound (e.g., nickel-based anti-seize) to the threads before tightening to prevent seizure.
  • Tighten slowly and steadily — avoid high-speed power tools which increase galling risk.
  • Do not exceed the rated tightening torque for the thread size and A2-70 grade.

Quality Assurance

  • Dimensional Inspection: 100% thread gauge inspection per ISO 965-1 (6g tolerance)
  • Material Verification: PMI (Positive Material Identification) / spectrometer analysis for SUS304 composition
  • Hardness Testing: Vickers hardness test per ISO 3506-3
  • Tensile / Proof Load Testing: Per ISO 3506-3 (A2-70)
  • Salt Spray Test: Corrosion resistance verification post-passivation
  • Socket Torque Test: Drive socket integrity verification
  • Lot Traceability: Full material and process traceability per batch

Packaging Options

  • Bulk (polybag or carton) — standard for wholesale orders
  • Small box (labeled, per size) — available for mixed or sample orders
  • Custom packaging — available for OEM and private-label customers

Ordering Information

  • Price: Unit price per piece (USD), not per thousand. Contact us for volume pricing.
  • Customer Base: B2B wholesale only. We do not serve retail / B2C customers.
  • Order Method: All orders are placed offline. Online prices are for reference and inquiry only. Please contact us via email to place orders.
  • MOQ: Varies by size — contact FULLERKREG for minimum order quantities.
  • Lead Time (Small Batch): Approx. 30 days, delivered DDP.
  • Lead Time (Large Volume): FOB Shanghai; other Incoterms negotiable.
  • Custom Orders: Non-standard lengths, special configurations, or OEM requirements available upon request.

Frequently Asked Questions

Q: What is the difference between DIN 916 and ISO 4029?
A: DIN 916 is the German standard; ISO 4029 is the international equivalent. Both specify the same cup point set screw geometry and are dimensionally interchangeable. FULLERKREG products comply with both standards.

Q: What does A2 stainless steel mean?
A: A2 is the designation for austenitic stainless steel per ISO 3506-3, corresponding to SUS304 / 1.4301 (18% Chromium, 8–10% Nickel). It offers excellent general corrosion resistance and is the most widely used stainless steel grade for fasteners.

Q: What is passivation (洗白钝化)?
A: Passivation is an acid treatment process that removes free iron and surface contaminants from the stainless steel surface, restoring and enhancing the natural chromium oxide passive layer. The result is a bright, clean, silver-white finish with improved corrosion resistance.

Q: Are A2 stainless set screws suitable for marine environments?
A: A2 (SUS304) provides good resistance to light marine and coastal environments. For direct seawater immersion or high-chloride splash zones, A4 (SUS316) is recommended. Contact FULLERKREG if you require A4 grade.

Q: Why do stainless steel set screws sometimes seize during installation?
A: Stainless steel is prone to galling (cold welding) due to its tendency to work-harden under friction. To prevent this, always apply an anti-seize compound to the threads before installation and tighten slowly by hand or with a calibrated torque wrench.

Q: Can A2 stainless set screws lock onto hardened shafts?
A: A2 stainless has moderate surface hardness (HV 200–300). It can engage unhardened and lightly hardened shafts effectively. For very hard shafts (HRC 40+), alloy steel 45H/12.9 grade set screws provide superior bite and holding force.

Q: Do you offer custom lengths or thread pitches?
A: Yes. FULLERKREG can produce non-standard configurations. Please contact us with your technical requirements.

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