the key insert also named keylocking threaded insert and keylocked threaded insert in abroad.they may be used in alloys,light materials,steel and cast iron to increase the strength of the thread in these materials.They can also be used for thread repair,whereas the defect thread can be replaced with the same nominal dimeter.
key insert have less attrition.A multiple tightening and loosening of the bolt is possible.locking inserts include a dry film lubrication on the surface to protect the screw from galling.
key insert have a positive lock against rotation and vibration.
key insert usually have 2 or 4 pre-assembled kees depending on the diameter.after installation of the kees into the parent material the assembly in form-closed.No check with a thread gauge in the area of the kees.
Pull-out-strength for key insert calculation as follows:
Pull-out-strength(N)=shear engagement(mm2)*ultimate shear strength of parent material(N/mm2).