What Are Keenserts®?

“Keensert,” otherwise known generically as “key-locking insert,” is the trademarked name for a type of metal threaded insert fastener in which keys are hammered into grooves through the threads, permanently locking the insert where installed.

Keenserts come in a variety of styles for a wide range of applications, including miniature, thinwall, lightweight, heavy duty, extra heavy duty, locking, non-locking, locking, solid and floating styles. 

Major brands that manufacture Keenserts® include Acme, Alcoa, Camloc, Clarendon, Fairchild, Kaynar, Microdot and Tridair Keenserts, which either currently or have historically manufactured these key-locking inserts in imperial, metric and mil-spec sizes and materials.

How Do Keenserts® Work?

A Keensert® is hammered with keys that lock the insert to the workpiece during installation. The locking keys are mounted in dove-tail groove features cut into the insert body. At the final step of the installation of Keenserts, the keys are driven deeper into the dovetail slots to effectively lock the insert to the workpiece housing.

They key-locking inserts are threaded into a pre-tapped hole, and then the “keys” are driven down into the tapped threads, providing a mechanical lock against rotation, especially when the mating stud or bolt will be removed frequently.

Key-locking inserts can be internally self-locking or non-locking. Non-locking inserts are more popular and are sufficient for the most common applications, allowing for more flexibility in their usage post-installation.

Inserts with the internal self-locking feature are designed to securely lock a bolt when it is entered into the insert with only a few turns. Even after repeated installations and removals of the bolt, the lock maintains sufficient locking torque to prevent the bolt from vibrating out.

In comparison to “Heli-coil®,” or Helical wire inserts, a related type of threaded insert,  Keenserts are typically stronger and easier to install than their Heli-coil counterparts, but they can tend to be more expensive as well. In heavy wear, high-vibration and high-heat situations, where saving space is not a concern and hole depth is limited, key-locking inserts are the best bet. When reducing costs and minimizing space are priorities, Helical wire inserts are the way to go

Examples of Keensert Application

Keenserts are used in alloys, light materials, steel and cast iron — wherever there is need to increase the strength of the thread in such materials. Industries such as manufacturing, aerospace, electronics and automotive are common use cases for key inserts and other threaded inserts. They can also be used for thread repair, if the defected thread has to be replaced with the same nominal diameter.

Examples of the various styles of Keenserts being used in industry include:

  • Miniature key-locking inserts are used in electronic and aerospace applications where size and strength are critical. (These inserts may be installed in sheet material as thin as 1/16″.)
  • Thinwall Keenserts have smaller external threads than standard heavy duty inserts and are ideal for tight spaces where less pull-out strength is acceptable.
  • Heavy duty inserts feature a thick, heavy-duty thread wall, suitable for most applications, but especially where the fasteners’ strength will be tested.
  • Extra heavy duty inserts are used in oversized and overly worn holes.

In general, key-locked inserts are used for thread repair and to strengthen threads. The benefit of these threaded inserts is that they can be used to repair a stripped threaded hole, mold or cast threads into a work piece, provide a durable threaded hole in a soft material, or simply to change from unified to metric threads. Both helical wire and key-locking inserts are commonly used in the manufacturing and repair of aerospace assemblies and electronic equipment, with Keenserts offering the benefits of strength and ease-of-installation cited above.

If you have questions regarding which fasteners are ideally suited to meet your particular needs, visit for an overview of the complete range of commercial and mil-spec fasteners.