Whether you’re fixing an oversized or misplaced hole or need to complete a repair on original equipment (OEM), key locking inserts are the ideal fastener for repairing damaged threads.
What Are Key Locking Inserts?
Key locking inserts are solid, single-piece inserts that are threaded both internally and externally. Offering a positive mechanical lock to prevent rotation caused by vibration or torsion, these inserts are often known by the shorthand “keysert,” but Keysert® is actually the registered trademark of Alcoa Fastening Systems.
They are easy to install with a standard drill or tap, which also makes them easy to removed without damaging the parent material. Below are the four main styles of key locking inserts.
- Thin Wall: With a smaller external thread size than the more standard heavy duty inserts, Thin Wall inserts are perfect for tight spaces where less pull-out strength is required.
- Heavy Duty: As the standard key locking insert suitable for most applications, Heavy Duty inserts are general purpose and have a thick and heavy-duty thread wall. These inserts are ideal for applications where the mating stud or bolt will be removed regularly.
- Extra Heavy Duty: Supplying greater pull-out strength, longer life, and stability, Extra Heavy Duty inserts have greater external thread area and an increased wall thickness. Their ideal use is with materials with lower ultimate shear strength, which allows for maximum pull-out strength and integrity.
- Solid: These inserts are ideal for relocating misplaced holes, plugging holes, salvaging expensive castings, or filling in holes that are too big.
Key locking inserts are excellent for use in reinforcing softer materials, such as magnesium or aluminum, and can be used in countless other materials, including cold-rolled steel, cast iron, and even plastic.
Some of the most common uses for key locking inserts include:
- Tool and die
- Heavy machinery
- Small engines
Advantages of Key Locking Inserts
If you’re deciding between a key locking insert or another insert, there are some major benefits to the former. The danger of using a helical threaded insert is that these inserts are usually designed with a “tang,” or piece of material at the bottom of the insert that is the catch point for the installation tool. After installation, the tang is broken off and can end up loose in the chassis of your application. In certain applications, this can cause an electrical short or other malfunction. With a key locking insert, there is no danger of a tang or other component of the fastener ending up loose in the chassis, making it a safer, more secure solution.
In addition to being durable and strong, key locking inserts also have the benefit of being installed using standard tools or by hand—there’s no need for a pre-winder tool. Even better? With key locking inserts, cross threading is nearly impossible.
How to Install
To install a key locking insert to repair a damaged thread, follow these steps:
- Drill out the old thread with a standard drill and chamfer the new hole with a standard sink.
- Tap the new thread with a standard tap.
- Screw the key locking insert in place by hand first, and then use an installation tool to thread it down until it’s resting slightly below the surface.
- Position the installation tool so the grooves are not aligned with the keys and, using a hammer, tap the keys down into the insert to secure the installation.
To uninstall a key locking insert, simply drill out the material between the keys and the internal thread with a standard drill. Then, deflect the keys inward and break them off. You can then remove the insert using a standard screw extracting tool, and a same-size replacement insert can be installed into the original hole.
Not sure what type of key locking insert you need for your application? Request a quote and take advantage of our fastener experts’ years of experience and knowledge to make sure you’ve got the right key locking insert for the job.