Threaded Inserts: How to Put Them In


Threaded inserts are metal or plastic components used in fasteners. Typically, they’re employed to create screw or bolt threading. These inserts can repair a damaged thread track, install threads into a workpiece, or attach more securely to soft or malleable surfaces that might resist linking. Typically used to fill an existing hole or slot, threaded inserts have a cylindrical inner cavity lined with threads and an exterior design that allows them to be lodged securely.

Inserts for fasteners come in various materials, from metals like brass and steel to plastics like PVC. Similarly, they come in different styles to suit multiple needs. Injection-molded inserts are utilized in plastic fabrication holes, whereas key-lock inserts are used to fix damaged threads. While threaded brass inserts can be used in various applications, they primarily secure plastic. Installing these inserts is a multi-step operation that may call for specialized tools or methods.

Wood with Threaded Inserts

Care must be taken while inserting a threaded brass insert into a wooden surface. You’ll need a copper tube with an inside diameter somewhat more significant than the external diameter of the threaded rod, some masking tape, and a couple of nuts of comparable size, depending on the needs of your application.

Before inserting the threaded insert, a pilot hole must be bored into the wood. Mounting the workpiece in a drill press can help maintain a perpendicular insertion angle to the surface. Still, the drill press must be turned off throughout the procedure. Clamping the workpiece too tightly can prevent the threaded rod from turning freely inside the copper sleeve, which is why a loose fit is necessary. The rod is twisted into its slot with a wrench, and the copper tubing (a sleeve) is held with masking tape. Considerations for clearing the region of chips may be necessary depending on the hardness of the wood.

Thermoplastic Inserts with Threads

It takes different tools and techniques to install threaded brass inserts in a thermoplastic material like acrylic, as opposed to wood. Melting the insert into the workpiece might create a strong bond between the two. When working with acrylic, this is typically done on the smoother side so that less melted plastic collects around the insert, making it more straightforward to set up. The typical procedures in such a method include:

A threaded brass insert typically features a taper on one side to facilitate its placement within a slot. The thermoplastic workpiece should have a sequence of predrilled holes along its surface, and the inserts should be positioned there.

A heated soldering iron can be inserted into the threaded insert after the workpiece has been clamped or shifted such that the insert holes protrude over the edge of a bench or other work surface. The insert can be driven straight into the material by applying light pressure to the soldering iron.

Inserts can be guided into the workpiece with the help of a soldering iron, allowing for a straighter protrusion. Although a tiny amount of melted plastic may rise above the insert, it should be pressed down until it is flush with the top surface of the workpiece. The insert’s flushness with the lower half of the plastic cover may also need to be examined, depending on the nature of the application.

After placing the threaded insert, you can double-check its alignment using a screw or bolt for inspection. If the screw is attached at an angle, you can straighten it out with a soldering iron.

Preheating the insert on the soldering iron before installation is recommended when working with a large brass insert. You can also use a drill press to hold the workpiece still while you heat the insert, but you shouldn’t operate the media at any point.

Dr. Ilya Leybovich
Author on Staff at

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