The HeliCoil is a popular brand of thread repair and thread creating insert offered by Emhart Teknologies, Shelton, CT. A HeliCoil is a coiled-wire type of insert used to create internal screw threads which will accommodate standard-sized fasteners.
You may not have been aware, but HeliCoils were developed, not to repair threads, but to make stronger threads in weaker materials, such as aluminum. Primarily for aircraft, the HeliCoil was created in 1938 as new aircraft designs required lighter materials. These lighter materials did not always have the proper strength to support a threaded fastener. The solution was a thread insert made of a very high strength alloy. In addition to stronger threads, the insert also distributes the load more equally amoung the threads.
Check out this video on the creation of the Threaded Insert:
