Titanium nylock nut is a prevailing torque type lock nut that integrates a titanium alloy body with a non-metallic nylon insert to create a highly reliable, reusable locking fastener. The core structure consists of a precision-machined hexagonal (hex), hex-flange, or 12-point flange nut body made from titanium alloy bar stock. A ring of nylon (typically PA66) is securely crimped into a collar at the top of the nut, occupying approximately the top one-third to one-half of the nut’s height. The internal diameter of this nylon ring is slightly smaller than the major diameter of the mating bolt .
The locking principle is based on elastic deformation and friction. When the bolt is threaded into the nut, it first engages with the standard metal threads. As it advances into the section containing the nylon insert, the bolt threads must force their way through the undersized nylon ring. This action creates radial pressure and significant frictional resistance, generating a prevailing torque that effectively resists loosening under vibration, thermal cycling, and dynamic loads. The nylon also acts as a thread sealant, helping to prevent moisture and contaminant ingress .
2. Material Grades and Properties
Titanium nylock nuts are available in various grades, each offering a distinct balance of strength, ductility, and corrosion resistance. The choice of grade is critical for application-specific performance .
The table below summarizes the key titanium grades used for these nuts.
|
Grade
|
Common Alloy Name
|
Key Characteristics and Typical Applications
|
|---|---|---|
|
Grade 1
|
Commercially Pure Titanium
|
Unalloyed titanium offering excellent ductility and formability. Highest corrosion resistance but lowest strength. Used in applications requiring maximum corrosion resistance where mechanical loads are low .
|
|
Grade 2
|
Commercially Pure Titanium
|
The most common grade of unalloyed titanium. A good balance of strength, ductility, and corrosion resistance. Widely used in general industrial, chemical, and marine applications .
|
|
Grade 5
|
Ti-6Al-4V (TC4)
|
The most widely used titanium alloy. Offers an excellent strength-to-weight ratio and good fatigue resistance. The premier choice for aerospace, automotive racing, medical implants, and high-performance sports equipment .
|
|
Grade 7
|
Ti-0.15Pd
|
Similar to Grade 2 but with added Palladium for enhanced crevice corrosion resistance, especially in reducing acids. Suitable for chemical process applications .
|
|
Grade 9
|
Ti-3Al-2.5V
|
A compromise between the fabricability of Grade 2 and the strength of Grade 5. Good cold-forming properties. Often used in aerospace tubing and hydraulic lines .
|
|
Grade 12
|
Ti-0.3Mo-0.8Ni
|
Excellent high-temperature strength and corrosion resistance, similar to some stainless steels. Used in heat exchangers and chemical processing equipment .
|
|
Grade 23
|
Ti-6Al-4V ELI
|
A higher purity version of Grade 5. Enhanced fracture toughness and improved ductility. Primarily used in medical implants and critical aerospace applications .
|
Typical Mechanical Properties for Key Grades:
-
Grade 2 (CP Titanium): Yield Strength: Min. 275 MPa, Tensile Strength: Min. 345 MPa, Elongation: 20% Min .
-
Grade 5 (Ti-6Al-4V): Tensile Strength: 950-1050 MPa, Yield Strength: 870-925 MPa, Elongation: 14-18%, Hardness: 30-40 HRC .
3. Standards, Specifications, and Sizes
Titanium nylock nuts are manufactured according to various international standards that define their dimensions, mechanical properties, and functional requirements .
-
Dimensional Standards:
-
DIN 985 / ISO 7040: Standard hex nylon insert lock nuts .
-
DIN 6923: Hex flange nylon insert lock nuts .
-
DIN 934: Standard hex nuts (basis for some nylock designs) .
-
-
Material Standards: The titanium material is often certified to ASTM B348 / ASME SB-348 .
Standard metric thread sizes range from M3 to M24, and imperial sizes from #2 to 1″ are commonly available. Custom sizes can be manufactured to order .
The table below provides example dimensions for Titanium Hex Flange Nylock Nuts (based on DIN 6923) .
|
Size
|
Thread Pitch (mm)
|
Flange OD (mm)
|
Height (mm)
|
Wrench Size (mm)
|
|---|---|---|---|---|
|
M6
|
1.0
|
14.2
|
6
|
10
|
|
M8
|
1.25
|
17.9
|
8
|
13
|
|
M10
|
1.25
|
21.8
|
10
|
15
|
|
M12
|
1.25
|
26.0
|
12
|
18
|
4. Advantages and Limitations
Advantages:
-
High Strength-to-Weight Ratio: Titanium provides strength comparable to steel at about 45% of the weight, crucial for aerospace and performance vehicles .
-
Excellent Corrosion Resistance: Titanium’s stable oxide layer offers superior resistance to corrosion in marine, chemical, and other harsh environments compared to steel .
-
Superior Vibration Resistance: The nylon insert effectively prevents self-loosening under severe vibration, outperforming standard nuts and lock washers .
-
Non-Magnetic and Biocompatible: Essential for applications in medical imaging (MRI), sensitive electronics, and medical implants (using biocompatible grades like 23) .
-
Reusability: Can be reused several times, though with a gradual reduction in locking torque .
Limitations:
-
Temperature Limit: The primary limitation is the nylon insert. While titanium can withstand temperatures over 500°C, the nylon insert begins to soften at approximately 120°C – 135°C (for PA66), leading to a loss of locking torque. For high-temperature applications, all-metal locking nuts are recommended .
-
Limited Reusability: For critical applications, they are considered limited-use components and should be replaced after a set number of cycles or during major overhauls .
-
Cost: Titanium and its machining process are more expensive than steel, making these fasteners a premium choice .
5. Surface Treatments and Identification
Surface treatments enhance both aesthetics and performance. A common finish is anodizing, an electrochemical process that creates a durable, colored oxide layer on the titanium. Common colors include Blue, Gold, Purple, Black, Red, Green, and Rainbow . This color coding can be used for torque identification, project stages, or aesthetic customization in consumer products like bicycles and motorcycles .
6. Applications
Titanium nylock nuts are specified in demanding industries where their unique properties provide critical advantages :
-
Aerospace & Aviation: Aircraft structures, engine mounts, landing gear components, and control linkages.
-
High-Performance Automotive & Motorcycle Racing: Suspension systems, brake components, and engine accessories.
-
Marine & Offshore: Pump skids, subsea instruments, and structures exposed to seawater.
-
Medical Devices: Surgical tools and non-implantable medical equipment (using biocompatible grades like 23 for implants).
-
Chemical & Energy Sectors: Heat exchangers, reactors, and piping systems in corrosive environments.
