A threaded insert is a cylindrical tube-shaped piece of metal with an internal thread. Threaded inserts are designed to be placed into existing holes to provide a threaded receptacle so that screws, bolts or other fixings can be installed. Threaded inserts with an external thread are also used to strengthen existing threads or to repair damaged threads usually in metalwork.
How to fit a threaded insert
The first step is to drill, mill tap or cut a hole of the recommended size into the material the insert will be embedded. The second step depends entirely on the type of insert, the material it will be used with and how the insert will be fitted.
Types of Threaded InsertFor plastic
Plastics are generally categorized into two main types Thermoplastic and Thermoset. These two plastics may sound similar but their physical characteristics are very different. Therefore the type of insert used is different.
• Thermoset
Thermoset plastics, due to cross-linking polymers at the curing stage enhance the materials physical and mechanical properties. This process makes thermoset plastic easier to mill and drill, so a press-fit threaded insert is better for this application.
• Thermoplastic
Threaded inserts for thermoplastic materials are more specialized and require a slightly different approach. Inserts are installed by heating the metal insert to a specific temperature. Once the desired temperature is reached the threaded insert is pressed onto the plastic. The heat from the metal melts the plastic and the insert fits into the desired position. When the plastic cools the insert is retained.
Threaded inserts for metal
Threaded inserts for metal have an external thread. The insert is simply matched by thread size and screwed into the existing threaded hole.
Threaded inserts for wood
It is possible to use both press-in and thread-in inserts in wood. If however a hardwood is being used it is advised to prepare a slightly larger hole than the insert and secure with a suitable adhesive. Hardwoods have a higher chance of cracking than other woods.
Materials and finishes
Threaded inserts are available in various materials and finishes and metric course threads to suit every application.
• Brass
• Steel
• Stainless Steel (316 & 302)
• Bright zinc plated
• Clear passivated
• Galvanised
• Plain
Thread sizes
M3, M3.5, M4, M5, M6, M8 and M10