Thread Knurled Insert Nuts for EV Manufacturing

Thread Knurled Insert Nuts for EV Manufacturing – Reliable Fastening Solutions for Electric Vehicle Systems

The rapid development of the electric vehicle (EV) industry has significantly increased the demand for lightweight structures, high-precision components, and reliable fastening technologies. Modern EV manufacturing integrates numerous engineering plastics, composite materials, and lightweight structural parts to reduce vehicle weight and improve energy efficiency.

However, plastic components alone cannot provide durable internal threads capable of withstanding high assembly torque, vibration, and repeated servicing. Threaded knurled insert nuts offer an effective solution by forming high-strength metal threaded connections embedded directly inside plastic components.

Through precision knurled surfaces and optimized embedding processes, these inserts provide reliable fastening points, improved assembly efficiency, and enhanced structural durability for critical EV components.

Key Functions of Thread Knurled Insert Nuts in Electric Vehicles

Threaded insert nuts—also known as threaded inserts or pre-embedded nuts—are widely used in EV plastic components to provide durable and reusable internal threads.

Their primary functions include:

Creating High-Strength Internal Threads

Engineering plastics used in EV components cannot maintain thread integrity under repeated assembly. Embedded metal inserts provide durable threads capable of supporting long-term mechanical loads.

Improving Structural Reliability

The external knurled structure—such as straight knurling, diamond knurling, or herringbone patterns—forms a strong mechanical interlock with plastic materials, preventing rotation or pull-out.

Supporting Lightweight Vehicle Design

Replacing traditional metal fastening structures with plastic components reinforced by insert nuts significantly reduces overall vehicle weight while maintaining mechanical strength.

Enhancing Assembly Efficiency

Threaded inserts allow automated installation during injection molding or post-processing, improving production efficiency and consistency.

Major Application Areas in EV Manufacturing

Threaded knurled insert nuts play a critical role in multiple systems within electric vehicles.

Power Battery Systems

In EV battery packs, numerous plastic or composite parts require reliable threaded connections. Insert nuts are commonly embedded in:

• Battery pack housings

• Battery module brackets

• Protective covers

• Structural plastic frames

These inserts provide strong threaded mounting points for assembling battery modules and allow easy maintenance or replacement.

Materials such as environmentally friendly brass (C3604) or stainless steel are widely used to ensure corrosion resistance and compliance with automotive safety standards.

Electric Motors and Electronic Control Systems

Threaded inserts are frequently used in plastic structures within:

• Motor housings

• End caps

• IGBT module housings

• Power electronics enclosures

These components require metal-plastic composite connections that balance mechanical strength with thermal conductivity, ensuring stable operation of high-power electronic systems.

Vehicle Interior and Structural Components

Thread knurled insert nuts are also widely used in injection-molded components throughout the vehicle interior and body structure, including:

• Seat mounting brackets

• Dashboard support structures

• Wiring harness fixing components

• Interior panel assemblies

Replacing traditional metal nuts with embedded inserts can reduce weight by approximately 25–35% in certain structural parts, supporting EV lightweighting strategies and improving vehicle range.

Charging Interfaces and High-Voltage Connectors

Charging ports and high-voltage connectors require extremely reliable fastening solutions to ensure durability under repeated plug-in cycles.

Thread knurled inserts are commonly used in:

• Charging socket housings

• High-voltage connector assemblies

• Electrical interface modules

These inserts ensure strong threaded connections while maintaining electrical and structural reliability in high-voltage environments.

Technical Advantages in EV Production

Thread-knurled insert nuts offer several key advantages that align with the technical requirements of electric vehicle manufacturing.

Lightweight Engineering

By replacing metal structural parts with reinforced-plastic components, EV manufacturers can significantly reduce vehicle weight. In some designs, lightweight materials supported by threaded inserts contribute to overall vehicle weight reductions of up to 100 kg.

High Mechanical Bonding Strength

The knurled outer surface of the insert forms a mechanical bond with the plastic during installation. This structure provides excellent resistance to:

• Pull-out forces

• Torque loads

• Long-term vibration

These characteristics are essential for components operating under continuous mechanical stress.

Compatibility with Automated Manufacturing

Thread insert nuts support multiple installation processes compatible with automated production lines, including:

• Hot-melt insertion

• Ultrasonic embedding

• Injection molding pre-embedding

These processes allow high-volume EV production with stable installation quality and reduced assembly time.

Compliance with Automotive Environmental Standards

Most modern insert nuts used in EV manufacturing are produced using RoHS-compliant brass materials, such as C3604, ensuring compliance with environmental and automotive material regulations.

Manufacturing Process Considerations

For optimal performance, the integration of thread knurled insert nuts requires precise process control during plastic molding and assembly.

Injection Molding Integration

During injection molding, inserts can be positioned inside the mold cavity before plastic injection. The molten plastic then flows around the knurled surface, creating a strong mechanical bond.

To ensure proper installation, mold hole diameter tolerances are typically controlled within ±0.05 mm, ensuring secure insert positioning and optimal bonding strength.

Automated Insert Feeding Technology

Recent technological developments have improved the efficiency of automated insert installation.

For example, in March 2024, the Chinese manufacturer Inpu Plastics applied for a patent titled “Nut Feeding Device for Injection Molded Parts Processing of New Energy Vehicles” (CN 222201418 U).

This technology addresses positioning deviations during automated insert feeding and improves installation accuracy in high-volume EV production environments.

 Materials and Typical Specifications

Threaded knurled insert nuts used in EV manufacturing are typically available in a range of materials and sizes.

Common Materials

• Lead-free brass (C3604)

• Brass alloys (H59, H62)

• Stainless steel (SUS303, SUS304)

Typical Thread Sizes

• M2 – M6 for electronic modules

• M4 – M8 for structural plastic parts

Dimensions are usually customized according to the structural design of EV components.

 Future Trends in EV Fastening Technology

As electric vehicles continue to evolve toward higher energy density, lighter structures, and intelligent electronic systems, the demand for reliable fastening solutions will continue to grow.

Thread knurled insert nuts support these trends by providing:

• Durable metal threads in lightweight plastic components

• Efficient compatibility with automated manufacturing

• Improved structural performance for critical EV systems

These advantages make threaded inserts an essential fastening technology in modern electric vehicle design and production.

Conclusion

Thread-knurled insert nuts provide a reliable, high-performance fastening solution for plastic components in electric vehicle manufacturing. Their precision knurled structures, robust materials, and compatibility with advanced molding processes allow EV manufacturers to achieve:

• High-strength threaded connections

• Improved lightweight design

• Enhanced assembly efficiency

• Long-term structural reliability

As the EV industry continues to expand, embedded threaded insert technology will play an increasingly important role in supporting the next generation of efficient, lightweight, and durable electric vehicles.