DIN 16903 threaded inserts

DIN 16903 threaded inserts, also known as plastic inserts or overmolding inserts, are metal components designed to be integrated directly into injection moulding processes to create durable and reliable internal threads in plastic parts.

These inserts are used when a standard thread formed directly in plastic is not sufficient to ensure long-term mechanical performance. Under conditions such as high loads, vibration, or repeated assembly cycles, plastic threads can wear or deform, reducing the reliability of the joint.

During the injection moulding process, the insert is placed inside the mould before the plastic is injected. The molten material flows around the component, creating a permanent mechanical interlock between metal and polymer after cooling.

Different geometries are available to meet specific application requirements. Hexagonal inserts provide high resistance to rotation, knurled inserts improve pull-out strength through enhanced surface grip, while flanged designs ensure precise positioning during moulding.

Material selection also plays a key role in performance. Brass is the most commonly used material due to its excellent balance of machinability, strength, and corrosion resistance, while steel and stainless steel are preferred for more demanding mechanical or environmental conditions.

DIN 16903 inserts are widely used across industries such as automotive, electronics, electromechanical systems, industrial automation, and technical equipment, where reliable threaded connections are critical for product performance and safety.

From a design perspective, key factors such as plastic material type, applied load, and installation method must be evaluated carefully. Incorrect selection can lead to rotation, pull-out, or premature failure of the insert.

Common issues in plastic assemblies include thread wear, insert rotation under torque, or structural failure during tightening operations. These problems are typically linked to improper insert design selection rather than material defects.

Although the DIN 16903 standard is officially withdrawn, its designation is still widely used in industry as a reference for this category of overmoulding threaded inserts.

Selecting the correct insert requires a technical evaluation of operating conditions, mechanical stresses, and the long-term behavior of the plastic material.

Ultimately, insert selection is not just a catalogue choice, but an engineering decision that directly impacts the durability and reliability of the final assembly.

ATS Lamberti supplies standard and custom DIN 16903 threaded inserts for injection moulding and overmoulding applications, supporting engineers and procurement teams in selecting the most suitable solution based on material, process conditions, and mechanical requirements.