Press Fit Inserts: A Complete Guide to Threaded Inserts for Plastic, Metal, and More
Press fit inserts, or press-in threaded inserts, are a great way to add long-lasting internal threads to materials that are too soft, thin, or not suitable for direct threading. These inserts are widely used in manufacturing, engineering, and product design to ensure that plastic, metal, and composite materials have strong, reusable threads.
A press fit threaded insert is designed to be installed into a pre-drilled hole using pressure, rather than heat or threading. Once installed, it creates a secure threaded connection for screws and bolts, improving durability and long-term performance.
What Are Press Fit Threaded Inserts?
Press fit inserts are fasteners with a knurled or textured outer surface and internal threads. They are pressed into a hole to create a strong, permanent thread.
These inserts are commonly used when:
- The base material does not hold threads well
- A stronger, longer-lasting threaded connection is required
- Repeated assembly and disassembly is needed
The knurled design, including diamond knurls, helps the insert grip the surrounding material, preventing rotation or pull-out during use.
Key Benefits of Press Fit Inserts
Strength and Durability
Press fit inserts improve thread strength in softer materials like plastic by distributing the load evenly and reducing stress concentration. EZ LOK designs help maintain structural integrity and prevent material splitting.
Secure and Dependable Connection
The press installation process ensures a tight fit. When a fastener is inserted, the insert expands slightly, increasing holding strength and preventing loosening over time.
Easy Installation Process
Press fit inserts do not require heat or specialized tools for installation, unlike heat set inserts.
Cost-Effective Manufacturing
Press fit inserts simplify the manufacturing process by reducing tooling requirements and minimizing errors during installation.
Materials and Options
Depending on the application, press fit inserts are available in a variety of materials:
- Brass – corrosion resistant and ideal for electrical and general applications
- Stainless steel – higher strength and durability for demanding environments
- Other metal options depending on specification requirements
They are also available in multiple sizes, lengths, and configurations, including:
- Flush inserts
- Flanged inserts
- Reverse slot designs
This range of options ensures compatibility with different hole sizes, components, and applications.
Applications of Press Fit Inserts
Press fit threaded inserts are used across many industries and manufacturing processes:
- Plastic components and housings
- 3D printing applications
- Electronics and enclosures
- Automotive and industrial equipment
- Assembly of multi-component systems
They are especially valuable in plastic applications where direct threading would not provide sufficient strength or durability.
Press Fit Inserts for Plastic
Press fit inserts are commonly used in both thermoplastics and thermoset plastics.
Thermoplastics
Thermoplastics can be reshaped with heat. Press fit inserts provide:
- Strong retention through knurled surfaces
- Resistance to torque and pull-out
- Clean installation without heat
Thermoset Plastics
Thermoset plastics are rigid and cannot be reshaped. In these materials, press fit inserts:
- Reduce the risk of cracking or breaking
- Provide a secure threaded connection
- Maintain material integrity during installation
Installation Process
Press fit inserts are easy and efficient to install.
Step-by-Step Guide
- Drill the correct hole size according to specifications
- Align the insert with the hole
- Press the insert into place using a tool (such as an arbor press)
- Insert the fastener to expand and secure the insert
During installation, the insert compresses slightly and then expands as the screw is installed, locking it firmly into the material.
Tools Used
- Arbor press
- Manual press tool
- Production press systems
Using the correct tool ensures proper alignment and consistent results.
Important Design Considerations
When selecting and installing press fit inserts, consider the following:
Hole Size
Choosing the correct hole size is critical. A hole that is too small may damage the insert, while a hole that is too large may reduce retention strength.
Material Compatibility
Different materials (plastic, metal, wood) require specific insert designs for optimal performance.
Length and Size
Selecting the correct insert length and internal thread size ensures compatibility with your fasteners and components.
Manufacturing Process
Consider how inserts fit into your overall manufacturing workflow, including assembly speed and consistency.
Press Fit Inserts vs Other Insert Types
Press fit inserts are one type of threaded insert.
Compared to other options:
- Heat set inserts require heat and are better suited for thermoplastics
- Threaded inserts (self-tapping) cut threads into the material
- Press fit inserts are easier, faster, and more cost-effective to install
They are ideal when you need a balance of strength, ease of installation, and production efficiency.
Why Choose EZ LOK Press Fit Inserts?
EZ LOK press fit inserts are designed to deliver:
- Reliable performance across plastic applications
- Easy, tool-friendly installation
- Strong, reusable threads
- A wide range of sizes, types, and materials
Their designs ensure secure installation while minimizing the risk of damage to the base material.
Press fit inserts are a flexible and dependable solution for creating strong, long-lasting threaded connections in a wide range of materials. Whether used in plastic components, manufacturing assemblies, or 3D printing applications, they provide a secure and cost-effective way to improve product performance.
By selecting the right type, size, and material—and following proper installation practices—you can ensure long-lasting results and efficient production.