FULLERKREG DIN 916 K Serrated-Locking Cup-Tip Set Screw — Alloy Steel ML40Cr | Grade 45H (12.9) | Black Oxide
FULLERKREG DIN 916 K serrated-locking cup-tip set screws are engineered for high-vibration and high-load applications where conventional set screws are prone to loosening. The knurled (serrated) locking ring beneath the hex socket head bites into the mating surface under torque, providing a mechanical anti-loosening effect without adhesives or secondary locking elements.
Key Features
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Standard: DIN 916 K (cup-tip set screw with serrated locking collar)
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Drive: Internal hex (Allen / hex socket), per ISO 4026 / DIN 916 geometry
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Point Style: Cup tip — provides a secure, non-marring grip on shafts and flat surfaces
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Locking Mechanism: Serrated (knurled) collar — mechanically locks against the mating surface to resist vibration-induced loosening
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Material: Alloy Steel ML40Cr (chromium-molybdenum alloy steel, equivalent to 40Cr per GB/T 3077)
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Strength Grade: 45H — equivalent to ISO 898-1 Grade 12.9 for set screws
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Surface Treatment: Black oxide (blackening) — corrosion inhibition, low reflectivity, dimensional neutrality
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Thread: Metric coarse thread (ISO 68-1), right-hand
Material & Mechanical Properties
Manufactured from ML40Cr alloy steel — a chromium-alloyed medium-carbon steel offering excellent hardenability, toughness, and fatigue resistance. Fully compliant with the mechanical requirements of ISO 898-1 and DIN 267-11 for property class 45H / 12.9 set screws.
| Property |
Value |
Standard Reference |
| Property Class |
45H (≡ 12.9) |
ISO 898-1 / DIN 267-11 |
| Minimum Hardness |
45 HRC |
ISO 898-1 Table 10 |
| Maximum Hardness |
52 HRC |
ISO 898-1 Table 10 |
| Vickers Hardness (min) |
450 HV |
ISO 898-1 |
| Minimum Torsional Strength |
Per ISO 898-1 Table 10 by size |
ISO 898-1 |
| Core Hardness |
390–460 HV |
DIN 267-11 |
| Material |
ML40Cr Alloy Steel |
GB/T 3077 / ISO equivalent |
Surface Treatment: Black Oxide
- Chemical blackening (black oxide) per applicable finishing standards
- Provides mild corrosion resistance — recommended for indoor or protected environments
- Adds no measurable dimensional change (unlike zinc plating)
- Low reflectivity — suitable for optical, precision, and aesthetic assemblies
- Typically applied with a light oil post-treatment for enhanced protection
Dimensional Reference (DIN 916 / ISO 4029 Cup-Tip)
| Size |
Thread Pitch (mm) |
Hex Key Size (mm) |
Cup Tip Dia. dk (mm) |
Common Lengths (mm) |
| M3 |
0.5 |
1.5 |
1.5 |
3, 4, 5, 6, 8, 10, 12 |
| M4 |
0.7 |
2.0 |
2.0 |
4, 5, 6, 8, 10, 12, 16 |
| M5 |
0.8 |
2.5 |
2.5 |
5, 6, 8, 10, 12, 16, 20 |
| M6 |
1.0 |
3.0 |
3.0 |
6, 8, 10, 12, 16, 20, 25 |
| M8 |
1.25 |
4.0 |
4.0 |
8, 10, 12, 16, 20, 25, 30 |
| M10 |
1.5 |
5.0 |
5.0 |
10, 12, 16, 20, 25, 30, 40 |
| M12 |
1.75 |
6.0 |
6.0 |
12, 16, 20, 25, 30, 40, 50 |
| M16 |
2.0 |
8.0 |
8.0 |
16, 20, 25, 30, 40, 50 |
| M20 |
2.5 |
10.0 |
10.0 |
20, 25, 30, 40, 50 |
All dimensions per DIN 916 / ISO 4029. Consult FULLERKREG product listings for exact available size/length combinations.
Locking Performance: How the Serrated Collar Works
The DIN 916 K variant adds a knurled (serrated) locking ring integrated at the base of the hex socket head. When the set screw is tightened:
- The cup tip engages the shaft or mating surface, transmitting axial clamping force.
- The serrated collar simultaneously bites into the bore wall or housing surface.
- The resulting mechanical interlock resists rotational loosening under dynamic loads, vibration, and thermal cycling — without thread-locking adhesives.
This makes DIN 916 K set screws ideal for shaft collars, shaft couplings, gear hubs, pulleys, and precision positioning assemblies subject to vibration or shock.
Typical Applications
- Shaft-to-hub locking in motors, gearboxes, and drive systems
- Shaft collars and couplings in industrial machinery
- Precision positioning in CNC fixtures and tooling
- Vibration-prone assemblies in automotive, robotics, and automation equipment
- Optical and instrumentation mounts requiring secure, non-marring fastening
- Replacement for standard DIN 916 where vibration loosening is a concern
Compliance & Standards
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DIN 916 — Hexagon socket set screws with cup point
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DIN 916 K — DIN 916 with serrated (knurled) locking collar
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ISO 4029 — Hexagon socket set screws with cup point (international equivalent)
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ISO 898-1 — Mechanical properties of fasteners made of carbon steel and alloy steel
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DIN 267-11 — Fasteners: Technical specifications — Property classes for set screws
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ISO 68-1 — Metric screw threads: General plan
Packaging & Supply
- Available in bulk bags, boxes, and custom packaging for OEM and MRO supply
- Wholesale and B2B pricing available — contact FULLERKREG for volume quotations
- Full material certifications (mill certs, hardness test reports) available on request
- RoHS compliant; REACH-compliant surface treatment
Why Choose FULLERKREG?
- Manufactured to DIN/ISO dimensional and mechanical standards — not just nominal equivalents
- Full traceability: heat number, material cert, and hardness test documentation available
- Consistent 45H / 12.9 hardness verified by Rockwell testing per ISO 898-1
- Black oxide finish applied in-process with oil post-treatment for shelf-stable inventory
- Competitive lead times for standard sizes; custom lengths and thread forms on request
