Home » DIN 915 / ISO 4028 Socket Set Screw Dog Point — Alloy Steel 45H Black

DIN 915 / ISO 4028 Socket Set Screw Dog Point — Alloy Steel 45H Black

DIN 915 / ISO 4028 — Socket Set Screw with Dog Point | Alloy Steel 45H | Grade 12.9 | Black Oxide

FULLERKREG DIN 915 / ISO 4028 socket set screws (grub screws) with dog point are manufactured to full DIN and ISO dimensional standards in alloy steel ML40Cr, heat-treated to 45H property class (equivalent to Grade 12.9), with a black oxide surface finish. The dog point — a precision-ground cylindrical extension beyond the thread — provides positive mechanical location and engagement, making these set screws the definitive choice for precision positioning, indexing, and shaft-locking applications where friction-based holding alone is insufficient.

Product Specifications

Parameter Detail
Standard DIN 915 / ISO 4028
Type Socket Set Screw (Grub Screw) — Dog Point
Drive Hexagon Socket (Hex Allen Key)
Material Alloy Steel ML40Cr (Chromium Alloy Steel)
Property Class 45H (Grade 12.9 equivalent per DIN 267-11 / ISO 898-1)
Surface Treatment Black Oxide (Blackening)
Thread Metric Coarse Thread (ISO 68-1)
Thread Tolerance 6H (internal) / 6g (external) per ISO 965
Tensile Strength Min. 1220 MPa
Hardness 39 – 51 HRC
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) 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.

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
  • High holding capacity — combined with 45H / Grade 12.9 clamping force, the dog point provides both mechanical and friction-based retention simultaneously
  • Keyway-free design — eliminates the need for a keyway on the shaft, simplifying shaft machining and reducing stress concentrations

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 — Alloy Steel ML40Cr

ML40Cr is a chromium-alloyed medium-carbon steel specifically selected for high-strength fastener production. Its composition and heat treatment characteristics make it the standard material for 45H / Grade 12.9 set screws.

Chemical Composition (ML40Cr)

Element Content (%)
Carbon (C) 0.37 – 0.44
Silicon (Si) 0.17 – 0.37
Manganese (Mn) 0.50 – 0.80
Chromium (Cr) 0.80 – 1.10
Phosphorus (P) ≤ 0.025
Sulfur (S) ≤ 0.025

Mechanical Properties — 45H Property Class (Grade 12.9 Equivalent)

Property Value Standard
Tensile Strength (Rm) Min. 1220 MPa DIN 267-11 / ISO 898-1
Proof Load Stress (Sp) Min. 1100 MPa DIN 267-11
Hardness 39 – 51 HRC (385 – 530 HV) DIN 267-11
Minimum Breaking Torque Per DIN 267-11 size table DIN 267-11
Heat Treatment Quenched & Tempered —

45H vs. Standard Property Classes

Property Class Material Tensile Strength Hardness Typical Use
14H Carbon steel Min. 700 MPa 22–32 HRC General purpose
22H Carbon / alloy steel Min. 900 MPa 32–39 HRC Medium duty
45H Alloy steel ML40Cr Min. 1220 MPa 39–51 HRC High-strength, heavy duty

45H is the highest standard property class for set screws per DIN 267-11, equivalent to Grade 12.9 in the ISO 898-1 bolt property class system.

Surface Finish — Black Oxide

  • Process: Hot alkaline blackening — a chemical conversion coating forming a thin magnetite (Fe₃O₄) layer on the steel surface
  • Appearance: Uniform matte black finish with a professional, low-reflectance appearance
  • Coating Thickness: Typically 1–2 microns — no significant dimensional change; dog point diameter tolerance (h8) is maintained
  • Corrosion Resistance: Moderate — provides basic protection against light oxidation; supplemental oil or wax treatment recommended for humid environments
  • No Hydrogen Embrittlement Risk: Black oxide does not introduce hydrogen into the steel — critical for Grade 12.9 / 45H fasteners where hydrogen embrittlement is a serious concern with electroplated alternatives
  • Adhesion: Excellent base for supplemental lubricants and thread-locking compounds
  • Temperature Resistance: Stable up to approximately 300°C

Typical Applications

The dog point’s positive mechanical engagement combined with 45H / Grade 12.9 clamping force makes these set screws the preferred choice for precision and high-load applications:

  • Precision Shaft Location: Locating gears, pulleys, sprockets, and couplings at exact axial positions on shafts using a drilled engagement hole — eliminates positional drift under load
  • Indexing & Detent Mechanisms: Engaging indexing holes in rotary tables, dividing heads, and indexing fixtures for repeatable angular positioning
  • Keyway-Free Shaft Assemblies: Replacing traditional key-and-keyway connections in applications where shaft machining complexity must be minimized
  • Machine Tool & Tooling: Securing and locating tool holders, boring bar cartridges, and adjustable cutting tool components
  • Automotive & Motorsport: Locating camshaft timing components, gear selectors, and drivetrain elements requiring precise, repeatable positioning
  • Robotics & Automation: Precise location of servo motor shafts, encoder discs, and actuator components where positional accuracy is critical
  • Jig & Fixture Building: Locating and locking adjustable stops, guides, and reference components in production tooling
  • Adjustable Mechanical Assemblies: Any assembly requiring the component to be removed, repositioned, and reinstalled at the same or different indexed positions

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
  • For indexed applications, use a jig or dividing head to ensure hole positions are accurately located

Installation Procedure

  • Thread engagement: Minimum engagement length = 1× nominal diameter; for maximum holding power, 1.5× diameter is recommended
  • 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; 45H allows significantly higher torques than standard grades
  • Lubrication: Apply molybdenum disulfide (MoS₂) paste or equivalent anti-galling compound to threads; ensures accurate torque-to-clamp-force conversion
  • Hex key: Use a high-quality, calibrated hex key of the correct size; worn keys risk rounding the socket at high torques
  • Locking: For high-vibration applications, apply medium-strength thread-locking adhesive to the threads before installation
  • Hydrogen embrittlement: Black oxide finish does not introduce hydrogen — safe for Grade 12.9 / 45H; never substitute with electroplated fasteners at this strength level without baking treatment

Recommended Tightening Torques (45H / Grade 12.9, MoS₂ Lubricated)

Thread Torque (N·m) — Reference
M3 0.45 N·m
M4 1.05 N·m
M5 2.10 N·m
M6 3.60 N·m
M8 8.80 N·m
M10 17.5 N·m
M12 30.0 N·m
M16 75.0 N·m
M20 145.0 N·m

Reference values for MoS₂-lubricated 45H / Grade 12.9 alloy steel set screws. For dry installation, increase values by approximately 25–30%. 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
  • DIN 267-11 — Technical delivery conditions for fasteners — set screws; defines 45H property class (tensile strength, hardness, breaking torque)
  • ISO 898-1 — Mechanical properties of fasteners made of carbon steel and alloy steel; Grade 12.9 reference
  • ISO 965-1 — Metric screw thread tolerances
  • 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, toolroom, and wholesale customers
  • Each pack labeled with: Part number, Thread size × Length, Material (ML40Cr), Property Class (45H), Standard (DIN 915 / ISO 4028), Surface (Black Oxide), 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)
  • Hardness testing per DIN 267-11 (39–51 HRC) on every production batch
  • Breaking torque testing per DIN 267-11 size requirements
  • Material certification available on request — confirms ML40Cr alloy steel composition
  • Thread gauge inspection (Go/No-Go) per ISO 965
  • Heat treatment records (quench & temper parameters) maintained for full traceability
  • Black oxide coating uniformity inspection on each batch
  • Dog point concentricity and surface finish verified on sample basis per batch

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: What is a dog point and how does it differ from a flat point?
A: A dog point is a precision-ground cylindrical pin extension beyond the threaded body of the set screw. Unlike a flat point, which relies entirely on friction against the shaft surface, the dog point engages a pre-drilled hole in the shaft, providing positive mechanical location. This means the component is positively retained axially and rotationally even if the set screw loses some clamping force, and the assembly can be disassembled and reassembled to exactly the same position.

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: What does 45H mean for set screws?
A: 45H is the property class designation for set screws defined in DIN 267-11. It specifies a minimum tensile strength of 1220 MPa and a hardness range of 39–51 HRC. It is the highest standard property class for set screws and is equivalent to Grade 12.9 in the ISO 898-1 bolt classification system.

Q: Why is black oxide used instead of zinc plating for Grade 12.9 set screws?
A: Electroplating processes (including zinc plating) introduce hydrogen into high-strength steel, creating a risk of hydrogen embrittlement — a form of delayed brittle fracture that can cause catastrophic failure without warning. Black oxide is a chemical conversion coating that does not introduce hydrogen, making it the safe and standard surface treatment for Grade 12.9 / 45H fasteners, as specified in ISO 4042 and DIN 267-11.

Q: Can the dog point set screw replace a key-and-keyway connection?
A: Yes, in many applications. The dog point engaging a drilled hole in the shaft provides both axial and rotational location without requiring a keyway to be machined into the shaft. This simplifies shaft manufacturing, reduces stress concentrations, and allows the connection point to be repositioned. However, for very high torque transmission applications, a key-and-keyway or spline connection may still be preferred. Consult your engineering team for load-critical applications.

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. For Grade 12.9 torques, always use a high-quality hex key to avoid rounding the socket.

Q: Can I get a material test certificate (MTC)?
A: Yes. FULLERKREG provides Mill Test Certificates on request, confirming the ML40Cr alloy steel chemical composition and heat treatment property class (45H).

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

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