China Factory Ensat 302 Self-Tapping Fastening Inserts repair sleeves Sandum/InsaiL offers a wide range of Self Tapping Threaded inserts for Aluminium, cast iron, plastics and NF metals. These available in sizes M2 to M30 and equivalent UNC, UNF and BSW threading. Self Tapping Threaded Insert is designed as a permanent fastener in materials which are of insufficient strength to sustain applied loads in threads tapped directly in to these materials or where thread wear occurs due to frequent assembly and disassembly. The Self Tapping Threaded Insert is a bushing with internal and external threads designed to tap its own threads and is driven into a drilled or cored hole. The thread cutting action is performed by the holes or by the slot on the pilot portion of the inserts.