Inserts are classified as two general types: those held in place by external threads and those that use some means other than threads (knurls, grooves, interference fit) for their holding power.

We have all done it, overtightened a bolt and blown out the threads. When a bolt starts to tighten up and then go suddenly loose, you know that the threads are toast and now you have a problem.

These requirements should be considered in selecting the best insert: shear strength of parent material, operating temperature, load requirement, presence of ...