The key distinction is between a free-running insert and a locking insert. A free-running type provides a standard internal thread, while a locking type adds resistance to loosening from vibration. Locking resistance can be useful in machinery or repeated-service assemblies, but it may not suit every bolt, torque procedure, or maintenance requirement.
Length also matters. A short insert may not provide enough thread engagement in a highly loaded joint, while an unnecessarily long insert can complicate a blind-hole installation. Choose the shortest length that provides the required engagement and fits the available hole depth.
Start with the bolt specification, including nominal diameter and pitch. Do not select an insert from the outside diameter alone: the installation hole requires a suitable tapped thread, and the insert must produce the intended internal thread after installation. Confirm whether the assembly uses metric or inch threads and keep the insert, installation tooling, and replacement bolt within the same thread system.
Match the insert to the parent material and service environment. A soft alloy, cast material, plastic component, or steel part can impose different requirements for thread strength, installation behavior, and pull-out resistance. For outdoor, chemical, marine, or high-temperature use, ask which insert material and finish are appropriate rather than assuming a standard option will perform adequately.
Check the hole geometry before ordering. Blind holes need enough depth for the insert and installation process, while through-holes may allow more flexibility. Confirm the required insert length, whether a tang or tangless installation is preferred, and whether the repair leaves enough surrounding material. A common mistake is specifying the bolt size but not the available hole depth or the condition of the damaged thread.
For an inquiry, provide the thread size and pitch, parent material, required insert length or available hole depth, and the operating environment. Also ask whether the required insert type, installation tools, and technical documentation are available for the intended assembly.
