Home » DIN 915 / ISO 4028 Socket Set Screw with Dog Point A4 Stainless

DIN 915 / ISO 4028 Socket Set Screw with Dog Point A4 Stainless

DIN 915 / ISO 4028 — Socket Set Screw with Dog Point | A4 Marine Stainless Steel | Bright Passivated

FULLERKREG DIN 915 / ISO 4028 socket set screws (grub screws) with dog point are manufactured to full DIN and ISO dimensional standards in A4 marine-grade stainless steel (SUS 316) with a bright passivated surface finish. The precision-ground cylindrical dog point provides positive mechanical location and engagement, while the A4 grade delivers superior corrosion resistance — including resistance to chlorides, seawater, and aggressive chemical environments — making these set screws the definitive choice for precision positioning in the most demanding corrosion-resistant applications.

Product Specifications

Parameter Detail
Standard DIN 915 / ISO 4028
Type Socket Set Screw (Grub Screw) — Dog Point
Drive Hexagon Socket (Hex Allen Key)
Material A4 Marine Stainless Steel (SUS 316 / 1.4401)
Property Class A4-70 (per ISO 3506-3)
Surface Treatment Bright Passivated (Electrochemical Passivation)
Thread Metric Coarse Thread (ISO 68-1)
Thread Tolerance 6H (internal) / 6g (external) per ISO 965
Tensile Strength Min. 700 MPa (A4-70)
Hardness Max. 220 HV (Vickers)
Size Range M3 — M20
Length Range 5 mm — 60 mm (size-dependent)
Point Type Dog Point (Extended Cylindrical Pin)
Head Type Fully Threaded, Headless (Grub)
RoHS Compliant Yes

Key Dimensions (DIN 915 / ISO 4028)

Thread (d) Hex Key (s) Dog Point Dia. (dp) h8 Dog Point Length (t) min. Common Lengths (l)
M3 1.5 mm 2.0 mm 1.5 mm 5, 6, 8, 10, 12 mm
M4 2.0 mm 2.5 mm 2.0 mm 6, 8, 10, 12, 16 mm
M5 2.5 mm 3.5 mm 2.5 mm 8, 10, 12, 16, 20 mm
M6 3.0 mm 4.0 mm 3.0 mm 8, 10, 12, 16, 20, 25 mm
M8 4.0 mm 5.5 mm 4.0 mm 10, 12, 16, 20, 25, 30 mm
M10 5.0 mm 7.0 mm 5.0 mm 12, 16, 20, 25, 30, 40 mm
M12 6.0 mm 8.5 mm 6.0 mm 16, 20, 25, 30, 40, 50 mm
M16 8.0 mm 11.0 mm 8.0 mm 20, 25, 30, 40, 50, 60 mm
M20 10.0 mm 14.0 mm 10.0 mm 25, 30, 40, 50, 60 mm

Dog point diameter (dp) is ground to h8 tolerance per DIN 915 / ISO 4028 for precise hole engagement. All dimensions per DIN 915 / ISO 4028. Consult FULLERKREG datasheet or contact us for full tolerance tables.

Dog Point — Design & Function

The dog point is a precision-ground cylindrical pin extension that protrudes beyond the threaded body of the set screw. Unlike friction-only point types (flat, cup, cone), the dog point engages a matching hole or slot in the mating shaft or component, providing positive mechanical location independent of clamping force alone.

Key Functional Advantages

  • Positive axial location — the dog point engages a drilled hole in the shaft, preventing axial movement regardless of vibration or load reversal
  • Positive rotational location — when engaged in a hole or slot, prevents shaft rotation relative to the hub without relying solely on friction
  • Repeatable repositioning — the set screw can be removed and reinstalled with the component returning to exactly the same position; ideal for indexed or adjustable assemblies
  • No shaft damage — the cylindrical dog point engages a pre-drilled hole cleanly; no marring, indenting, or deformation of the shaft surface
  • Keyway-free design — eliminates the need for a keyway on the shaft, simplifying shaft machining and reducing stress concentrations
  • Superior corrosion-resistant engagement — A4 stainless construction ensures the dog point does not corrode or seize in the shaft hole even in chloride-rich or chemically aggressive environments, maintaining clean disassembly throughout service life

Dog Point vs. Other Set Screw Point Types

Point Type Standard Holding Mechanism Repositionable Shaft Damage Best For
Flat Point DIN 913 / ISO 4026 Friction only Yes None Non-marring, frequent adjustment
Cup Point DIN 916 / ISO 4029 Friction + indent Limited Circular indent Permanent locking, soft shafts
Cone Point DIN 914 / ISO 4027 Friction + deep indent No Deep indent Permanent location, V-groove
Dog Point DIN 915 / ISO 4028 Friction + positive pin engagement Yes None (pre-drilled hole) Precision location, indexing, keyway-free
Oval Point ISO 4026 variant Friction only Yes Minimal Curved surfaces, pivot points

Material — A4 Marine Stainless Steel (SUS 316)

Chemical Composition

  • Chromium (Cr): 16.0 – 18.0%
  • Nickel (Ni): 10.0 – 14.0%
  • Molybdenum (Mo): 2.0 – 3.0% — the critical addition that defines A4 / 316 grade
  • Carbon (C): ≤ 0.08%
  • Manganese (Mn): ≤ 2.0%
  • Silicon (Si): ≤ 1.0%
  • Type: Austenitic stainless steel

Mechanical Properties — A4-70 (per ISO 3506-3)

Property Value
Tensile Strength (Rm) Min. 700 MPa
Proof Load Stress (Sp) Min. 450 MPa
Hardness Max. 220 HV (Vickers)
Magnetic Non-magnetic (annealed state)
Temperature Range −196°C to +400°C continuous

A4 vs. A2 — Why Choose Marine Grade for Dog Point Applications?

Property A2 (SUS 304) A4 (SUS 316)
Molybdenum Content None 2–3% (key differentiator)
Chloride Resistance Moderate Superior
Marine / Saltwater Use Not recommended Recommended
Pitting Resistance (PRE) ~18 ~24–26
Chemical Resistance Good Excellent
Dog Point Seizure Risk in Chloride Environments Higher — pitting can lock dog point in hole Lower — Mo-enhanced passive film resists pitting
Food / Pharma Wash-down Suitable (mild) Preferred (chloride cleaning agents)
Property Class A2-70 A4-70

For dog point set screws specifically, A4 is strongly preferred over A2 in any environment with chloride exposure: the dog point engages a blind hole in the shaft, creating a crevice geometry that concentrates chloride attack. A4’s molybdenum content provides critical resistance to crevice corrosion in this geometry.

Surface Finish — Bright Passivated

  • Process: Electrochemical passivation — removes free iron and surface contaminants from the stainless steel surface
  • Effect: Restores and enhances the natural chromium oxide passive layer; for A4, the molybdenum-enhanced passive film is fully activated by passivation treatment
  • Appearance: Bright, clean, silver finish — no coating thickness added, no dimensional change; dog point h8 tolerance is fully maintained
  • Compliant with: ASTM A967 / ISO 16048 passivation standards
  • No hydrogen embrittlement risk: No electroplating involved
  • Hygienic: Smooth, non-porous, non-contaminating surface; suitable for food, pharmaceutical, and clean-room environments

Typical Applications

The combination of A4 marine stainless steel, bright passivated finish, and dog point positive engagement makes these set screws the definitive choice for precision positioning in corrosive and demanding environments:

  • Marine & Offshore: Locating components in deck hardware, winches, rigging, steering systems, and offshore platform equipment exposed to seawater and salt spray; A4 prevents dog point seizure in shaft holes due to chloride-induced pitting
  • Coastal & Outdoor Installations: Architectural hardware, outdoor signage structures, and mechanical assemblies in salt-air environments requiring repeatable disassembly
  • Chemical Processing: Precision location of components in pumps, valves, agitators, and reactors handling chlorides, dilute acids, and corrosive process fluids
  • Food & Beverage Processing: Locating conveyor shafts, agitators, and filling machine components in wash-down environments using chloride-containing cleaning agents (CIP systems) where A4 is the preferred grade
  • Pharmaceutical & Medical: Precision location in sterilizable assemblies, clean-room equipment, and laboratory instruments requiring non-magnetic, non-reactive, autoclavable fasteners
  • Swimming Pools & Water Treatment: Pump and filtration system components exposed to chlorinated water where A2 would be susceptible to pitting
  • Desalination & Water Treatment Plants: Equipment handling brackish water and brine streams requiring maximum chloride resistance
  • Electronics & Precision Instrumentation: Non-magnetic location of encoder discs, sensor components, and optical assemblies in sensitive or MRI-adjacent environments

Installation Guidelines

Shaft Hole Preparation

  • Drill a hole in the shaft at the desired location to match the dog point diameter (dp) — refer to the dimension table above
  • Recommended hole tolerance: H8 (clearance fit with dog point h8) for easy engagement and removal; H7 for tighter location with minimal play
  • Hole depth should be at least equal to the dog point length (t) plus 0.5 mm clearance at the bottom
  • Deburr the hole entrance to prevent galling on the dog point during engagement
  • In marine or chemical environments, ensure the shaft hole is clean and free of corrosion products before engagement to prevent seizure

Installation Procedure

  • Thread engagement: Minimum engagement length = 1× nominal diameter (e.g., M6 requires min. 6 mm engagement)
  • Alignment: Align the dog point with the shaft hole before tightening; partial engagement will damage the dog point and hole
  • Tightening torque: Use a calibrated torque wrench — refer to the torque table below
  • Anti-galling lubrication: Apply molybdenum disulfide paste or PTFE-based lubricant to threads before installation; stainless-to-stainless assemblies are particularly susceptible to galling — lubrication is essential
  • Hex key: Use the correct size hex key (Allen key) — see dimension table above
  • Locking: For vibration-prone or marine applications, apply medium-strength thread-locking adhesive to the threads before installation
  • Do not over-torque: A4 stainless has lower hardness than alloy steel; over-torquing risks thread stripping or socket rounding
  • Periodic inspection: In severe marine or chemical environments, inspect and re-passivate or replace fasteners as part of scheduled maintenance

Recommended Tightening Torques (A4-70, MoS₂ Lubricated)

Thread Torque (N·m) — Reference
M3 0.30 N·m
M4 0.70 N·m
M5 1.40 N·m
M6 2.40 N·m
M8 5.80 N·m
M10 11.5 N·m
M12 20.0 N·m
M16 49.0 N·m
M20 96.0 N·m

Reference values for MoS₂-lubricated A4-70 stainless steel set screws. For dry installation, increase values by approximately 15–20%. Lubrication is strongly recommended for stainless-to-stainless assemblies to prevent galling. Always verify with your engineering team for safety-critical applications.

Standards & Compliance

  • DIN 915 — Socket set screws with hexagon socket and long dog point
  • ISO 4028 — Hexagon socket set screws with long dog point
  • ISO 3506-3 — Mechanical properties of corrosion-resistant stainless steel fasteners (set screws); A4-70 property class
  • DIN 267-11 — Technical delivery conditions for fasteners; stainless steel property classes
  • ISO 965-1 — Metric screw thread tolerances
  • ASTM A967 / ISO 16048 — Passivation of stainless steel
  • RoHS 2011/65/EU — Restriction of hazardous substances compliant

Packaging & Ordering

  • Available in standard retail packs, engineering bulk packs, and full-box quantities
  • Custom quantity packaging available for OEM and wholesale customers
  • Each pack labeled with: Part number, Thread size × Length, Material (A4), Standard (DIN 915 / ISO 4028), Surface (Bright Passivated), Quantity
  • Bulk orders: contact FULLERKREG for volume pricing and lead times

Quality Assurance

  • 100% dimensional inspection on critical sizes per DIN 915 / ISO 4028, including dog point diameter (h8 tolerance)
  • Material certification (Mill Test Certificate) available on request — confirms A4 / SUS 316 composition including Molybdenum content
  • Hardness and tensile testing per ISO 3506-3 batch requirements
  • Thread gauge inspection (Go/No-Go) per ISO 965
  • Dog point concentricity and surface finish verified on sample basis per batch
  • Salt spray corrosion testing available for qualification batches
  • Traceability: heat number and batch records maintained

Frequently Asked Questions

Q: What is the difference between DIN 915 and ISO 4028?
A: DIN 915 and ISO 4028 are technically equivalent standards for socket set screws with long dog point. DIN 915 is the German standard; ISO 4028 is the international equivalent. Dimensions and tolerances are identical — parts are fully interchangeable.

Q: Why choose A4 over A2 for dog point set screws specifically?
A: The dog point engages a blind hole in the shaft, creating a crevice geometry that concentrates chloride attack — the most aggressive form of stainless steel corrosion. A4 (SUS 316) contains 2–3% Molybdenum, which dramatically improves resistance to pitting and crevice corrosion in chloride environments. In marine, coastal, food processing (CIP wash-down), or chemical applications, A4 is strongly preferred to prevent the dog point from corroding and seizing in the shaft hole, which would make disassembly extremely difficult.

Q: What hole size should I drill in the shaft for the dog point?
A: The dog point is manufactured to h8 tolerance. For standard engagement, drill the shaft hole to H8 tolerance (clearance fit) for easy assembly and disassembly. For tighter location with minimal play, use H7. Refer to the dimension table above for the dog point diameter (dp) for each thread size.

Q: Can A4 stainless dog point set screws be used in seawater immersion?
A: A4 (316) stainless performs well in seawater splash and spray environments and is suitable for intermittent seawater immersion. For continuous full immersion in seawater, higher-grade alloys may be required depending on temperature and chloride concentration. Contact FULLERKREG for guidance on extreme marine applications.

Q: Why is lubrication especially important for A4 stainless set screws?
A: Stainless steel is particularly susceptible to galling — a form of adhesive wear where threads seize and weld together during tightening. This is especially common in stainless-to-stainless assemblies. Applying an anti-galling lubricant (MoS₂ paste or PTFE compound) before installation is essential to prevent galling and ensure accurate torque application.

Q: Can A4 dog point set screws be used in food processing equipment?
A: Yes, and A4 is the preferred grade for food processing environments that use chloride-containing cleaning agents (CIP systems, hypochlorite-based sanitizers). The Molybdenum content provides the additional chloride resistance needed in these wash-down conditions. The bright passivated finish provides a smooth, non-porous, non-contaminating surface suitable for food contact.

Q: What hex key (Allen key) size do I need?
A: Refer to the dimension table above. Examples: M3 requires a 1.5 mm hex key; M6 requires a 3.0 mm hex key; M10 requires a 5.0 mm hex key.

Q: How can I verify the material is genuine A4 / SUS 316?
A: FULLERKREG provides Mill Test Certificates (MTC) on request, confirming the chemical composition including Molybdenum content. This is the standard method for verifying A4 / 316 grade in engineering and procurement.

Q: Are these RoHS compliant?
A: Yes. FULLERKREG A4 stainless dog point set screws are manufactured without restricted hazardous substances and are RoHS 2011/65/EU compliant.

FULLERKREG — Precision Fasteners to DIN / ISO Standards. For technical support, custom sizes, or bulk quotations, please contact our engineering team.

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