Threaded Inserts

Threaded inserts are cylindrical fasteners with an internal thread, designed to be installed into a pre-drilled or pre-formed hole to create a durable threaded interface for screws, bolts, or other fixings. They are widely used to provide strong, wear-resistant threads in materials that may otherwise be too soft, thin, or prone to damage, such as plastics, wood, composites, sheet metal, and softer metals.

Threaded inserts are available in a wide range of sizes, materials, finishes, and fixing hole requirements to suit different applications and environments. Common options include plain, galvanised, zinc-plated, and passivated finishes, offering varying levels of corrosion resistance and durability.

RS Singapore supplies a comprehensive range of threaded inserts to meet the needs of maintenance, repair, and industrial assembly applications, ensuring secure and repeatable fastening performance across a variety of materials.

Types of Threaded Bushes

Threaded inserts, also called threaded bushes, are grouped by the base material they fasten into and the way they are installed.

For Plastics & Polymers

These inserts are designed to create durable threads in plastic components where repeated assembly and disassembly may be required.

• Thermal Inserts: Thermal, or heat-set, inserts are heated and pressed into a moulded or drilled hole in a thermoplastic part. The hot metal softens the surrounding plastic, which flows into the knurled body and hardens as it cools, anchoring the insert. They are used for thermoplastic mouldings and many 3D-printed parts.
• Ultrasonic Inserts: Ultrasonic threaded inserts are installed using equipment that applies high-frequency ultrasonic vibration and pressure. The vibration plasticises the surrounding thermoplastic at the insert interface so that it flows into the insert's undercuts, knurls, or retention features. As the plastic cools and solidifies, it locks the insert in place.

For Metals

They are used to reinforce, repair, or create threads in metal components that are subject to repeated use or high loads.

• Helical Inserts: Helical inserts are coil-shaped thread repair or thread reinforcement inserts, commonly made from stainless steel, brass, or other high-strength alloys. They are typically used to restore or strengthen threaded holes in metals such as aluminium, aluminium alloys, and other lower-strength parent materials.
• Key-Locking Inserts: Key-locking inserts are solid threaded bushings with both internal and external threads. During installation, locking keys are driven into the parent material to create a positive mechanical lock that helps prevent rotation. They offer high resistance to torque-out and pull-out, making them suitable for heavy-duty applications and assemblies exposed to vibration.
• Self-Tapping Inserts: Self-tapping inserts cut or form their own thread as they are driven into a pre-drilled hole, reducing or eliminating the need for a separate tapping operation. They provide strong thread reinforcement and high pull-out resistance, making them suitable for softer metals, thermoplastics, wood, and other materials where durable threads are required.

For Sheet Metal & Panels

These inserts create strong, permanent threads in thin sheet metal, panels, and hollow sections where conventional tapping is impractical.

• Self-Clinching Threaded Inserts: These inserts are pressed into punched or drilled holes in ductile sheet metal, causing the surrounding material to flow into the insert’s undercut or retention features to create a permanent and high-strength mechanical lock. They are typically installed using a press and are suitable where a flush or low-profile threaded fixing point is required.
• Rivet Bushes and Blind Threaded Inserts: These inserts create strong internal threads in thin sheet metal, panels, or hollow sections. They are installed using a setting tool that deforms the insert body to lock it in place. Blind threaded inserts are particularly useful where installation access is only available from one side of the assembly.

How Threaded Inserts Work

Threaded inserts create strong, durable internal threads by securely anchoring into the parent material and distributing fastening loads.

• Thread Reinforcement: Threaded inserts create a durable internal thread in materials that may not reliably withstand repeated fastening. By providing a pre-formed thread, they improve resistance to wear, stripping, and thread damage, especially in softer materials such as plastics, wood, or light metals.
• Mechanical Retention and Anchoring: Inserts are secured using external features such as knurls, barbs, external threads, expansion sections, or locking keys. These features prevent rotation and movement under load, ensuring the insert remains firmly fixed during repeated use.
• Load Distribution and Strength: By spreading the applied load over a larger surface area, threaded inserts improve pull-out strength and torque resistance, helping maintain joint integrity under repeated fastening or higher mechanical loads.
• Installation Methods: Depending on the material and insert design, threaded inserts can be installed by press-fitting, threading (self-tapping or screw-in), heat staking or ultrasonic insertion (for plastics), expansion, or clinching for sheet materials.
• Performance and Installation Factors: Proper hole preparation and installation are critical for reliable performance. Factors such as hole diameter, material thickness, parent material hardness, insertion temperature, installation torque, and tool alignment all influence pull-out strength, torque-out resistance, and thread durability.

Threaded Inserts Selection Guide

Choose a threaded insert based on the parent material, application, load requirements, and installation method.

• Base Material Compatibility: Select inserts designed for the parent material, such as plastics, metals, or wood. Different designs (e.g. heat-set, self-clinching, or helical inserts) are optimised for reliable retention and performance in specific materials.
• Size and Fit: Ensure the thread size, insert length, outside diameter, and hole diameter match the screw and application. Incorrect sizing or hole preparation can reduce retention strength and reliability.
• Load and Performance Requirements: Consider pull-out and torque-out resistance based on the expected load, vibration, and frequency of use. High-load or frequently serviced applications require inserts with greater retention and wear resistance.
• Installation Method: Choose an installation method that suits the material and production setup. Heat-set and ultrasonic inserts are commonly used in plastics, while press-fit or self-clinching inserts suit sheet metal. Also consider installation equipment and accessibility.
• Material and Environmental Conditions: Select materials and finishes (e.g. stainless steel, brass, zinc-plated steel) based on corrosion resistance, temperature exposure, and operating environment.
• Application Type: Use solid or specialised inserts to create new threads in soft or thin materials. For repairing damaged threads in metal components, helical or key-locking inserts are typically preferred.

Applications of Nut Inserts

Threaded inserts, also known as nut inserts, create durable internal threads in materials that are prone to thread wear or stripping. They are widely used across manufacturing, repair, and prototyping applications where reliable fastening and repeated assembly are required.

• Consumer Electronics: In plastic housings for laptops, phones, and other electronic devices, threaded inserts provide durable screw attachment points that can withstand repeated assembly and servicing. They help prevent thread wear and stripping that can occur when screws are installed directly into plastic.
• Drone Manufacturing: Drone assemblies often incorporate threaded inserts in lightweight plastic components to provide secure mounting points for motors and other hardware. The inserts help maintain reliable fastener retention in applications exposed to vibration and repeated loading.
• Automotive Repair: Helical and key-locking inserts are used to repair damaged or stripped threads in engine components and soft-metal castings. An example is the repair of spark-plug threads, where an insert restores a durable threaded connection without replacing the entire component.
• Commercial Furniture Manufacturing: Ready-to-assemble furniture is often supplied with pre-installed threaded inserts, providing durable metal threads in wood or composite panels for bolts and other fasteners. This allows repeated assembly and disassembly without rapidly wearing the fixing point.
• Hardware Prototyping: In functional prototyping and short-run production, heat-set inserts add durable threads to 3D-printed enclosures, jigs, and fixtures. They enable printed parts to accommodate bolted connections and repeated assembly without damaging the plastic.

Trusted Threaded Inserts Manufacturer Supplier in Singapore

RS is a trusted manufacturer and supplier of threaded inserts in Singapore, offering a wide range from leading brands such as Hank, Böllhoff, and RS PRO. Our prices are clearly listed online, making it easy to compare sizes, materials, finishes, fixing hole diameters, and pack options before ordering.

Orders can be placed online for delivery or collection, or by phone. The online ordering process is easy, allowing you to select quantities, choose delivery and payment options, review your order, and receive an order confirmation.

The RS range also includes related fasteners and retaining components, such as spring pins and circlips, helping you source multiple products from a single supplier.

Most in-stock items are available for next-working-day delivery, subject to availability, order value, and cut-off times, with full delivery details on our delivery page.