What is a thread insert?
In the world of mechanical fastening and repair, thread inserts are small components that solve big problems. Whether you're working with soft materials, repairing damaged threads, or designing parts that need to be taken apart and reassembled repeatedly, thread inserts are your go-to solution.
But what exactly is a thread insert? Let’s break it down.
A thread insert is a small cylindrical component made of metal (usually stainless steel, brass, or phosphor bronze) or plastic, that is inserted into a pre-drilled hole to provide a durable internal thread. Once installed, it allows screws and bolts to be securely fastened without damaging the base material.
Thread inserts are commonly used in:
Aluminum and magnesium components
Plastics and composite parts
Wood assemblies
Damaged or stripped threads in steel or cast iron
Soft materials like aluminum or plastic can easily wear out or strip when screws are frequently installed and removed. A thread insert provides strong, wear-resistant threads that extend the life of the assembly.
When an internal thread is damaged due to cross-threading or overtightening, a thread insert can restore the thread to its original size — often stronger than before.
According to Machinery’s Handbook, installing a helical thread insert in a stripped hole can restore up to 95% of the original thread strength.
Many thread inserts offer excellent resistance to loosening under vibration, especially locking inserts used in automotive, aerospace, and industrial machines.
Stainless steel inserts in aluminum parts prevent galvanic corrosion, improving reliability in marine or chemical environments.
There are several types, each designed for specific applications:
Made of coiled stainless steel wire
Installed into a tapped hole
Common for thread repair and aerospace use
Creates a free-running or locking thread
Have locking keys that are driven down after installation
Ideal for high-strength permanent threads
Often used in heavy-duty equipment and aerospace
Installed by pressing or melting into a plastic hole
Provides durable threads in 3D printed or molded parts
No pre-tapping required — the insert cuts its own thread
Suitable for wood, aluminum, and soft metals
Installed from one side (blind hole)
Common in sheet metal or tubing applications
Thread inserts are sized based on:
Outer diameter (matches hole size)
Inner thread size (matches the bolt or screw)
Length (can affect pullout strength)
Thread standard (metric, UNC, UNF, etc.)
Example: An M6 thread insert may have an outer diameter of 9mm and an inner thread of M6×1.0.
Thread inserts are found in many industries:
Automotive: Cylinder heads, engine blocks, plastic covers
Aerospace: Lightweight aluminum parts with frequent maintenance
Electronics: Threaded connectors in plastic enclosures
Furniture & Woodworking: Repeat assembly/disassembly without thread wear
3D Printing: Adding strong metal threads to plastic parts
If you manufacture metal or plastic components and your customers demand durability, thread inserts are a value-added feature.
If you're sourcing thread inserts from a factory, consider the following:
Material: Stainless steel for corrosion resistance; brass for electrical contact
Type: Helical vs. solid vs. self-tapping
Surface finish: Passivated, zinc-plated, or lubricated
Packaging: Bulk, preloaded kits, or customized assortments
As a direct manufacturer of precision-engineered thread inserts, we offer:
Metric and inch sizes
High-volume OEM supply
Custom thread inserts for non-standard applications
We also support installation tooling, technical assistance, and sample testing — helping global customers simplify procurement and increase production reliability.
A thread insert may be small, but its impact on mechanical integrity is enormous. Whether you're reinforcing soft material, repairing a stripped hole, or building precision assemblies, thread inserts are the cost-effective, engineering-approved way to add strength and repeatability.
Contact our experts today for a free quote or technical consultation.